Download document

INDUSTRY STANDARD

INDUSTRY PROVISION SYSTEM UNITS OF MEASUREMENT Eddy current meters SPECIFIC ELECTRICAL CONDUCTIVITY IN THE RANGE 14 - 37 MSm/m Verification method

OST 1 01117-85 Introduced for the first time

By Order of the Ministry of June 19, 1985 No. 298-65, the introduction date was set from July 1, 1986.

This standard applies to eddy current meters of electrical conductivity (hereinafter referred to as meters) of materials intended for measurements in the range from 14 to 37 MS/m, and establishes methods and means for their initial and periodic verification.

1. VERIFICATION OPERATIONS

1.1. When calibrating meters, the operations specified in table should be performed. 1.

Table 1

the name of the operation	Standard clause number	Obligation to carry out operations when
		release from production and repair	operation and storage
Visual inspection
Testing
Determination of metrological parameters
Determination of basic error
Determining the influence of detuning from changing the gap
Determining the influence of the edge effect
Determining the influence of product thickness
Determination of the influence of product surface roughness
Determination of parameters of the eddy current transducer

1.2. The parameters of the eddy current transducer (ECT) are determined when the meters are released from production and after the ECC is repaired.

1.3. Periodic verification must be carried out at least once a year.

1.4. If negative results are obtained during one of the operations, verification of the meter is stopped and the verification result is considered negative.

2. MEANS OF VERIFICATION

2.1. When conducting verification, the following means must be used:

A set of state standard samples of electrical conductivity with a certification error for electrical conductivity in the range from 14.0 to 33.3 MSm/m - no more than 0.55%, and in the range from 33.4 to 37.0 MSm/m - not more than 1% (numbers according to the State Register of Measures and Measuring Instruments from 1395-78 to 1412-78);

Bridge E7-4 with a resistance measurement range from 0.1 to 10.0 7 Ohms, with an inductance measurement range from 10 -5 to 100 H;

2.2. It is not allowed to verify meters using sets of state standard samples of electrical conductivity (hereinafter referred to as GSOue sets) used to adjust meters during operation.

3. CONDITIONS OF VERIFICATION AND PREPARATION FOR IT

3.1. When conducting verification, the following conditions must be met:

Ambient air temperature................................... 293 K ± 2 K (20 °C ± 2 °C );

relative air humidity................................... (65 ± 15)%;

3.3. Before carrying out verification, the following preparatory work must be completed:

Maintain the meter being verified and verification means under these conditions for at least 4 hours;

Ground devices operating from the network;

Prepare the meter to be verified and verification means in accordance with the operating instructions.

4. VERIFICATION

4.1. Visual inspection

Availability of space for branding.

4.2. Testing

4.2.1. Check the smoothness of movement and the clarity of fixation in the specified positions of the controls, and the compliance of their actions with the inscriptions on the meter panel.

4.2.2. Check the overall performance of the meter according to the technical description.

4.3. Determination of metrological parameters

4.3.1. Determination of the main error of meters is carried out using the GSOUE kit, depending on the type of indicator device of the meter being verified.

4.3.1.1. Determination of the main error of meters that have a digital display board or a pointer device calibrated in units of electrical conductivity as an indicator device is carried out as follows.

Configure the meter to be verified in accordance with the technical documentation for this type of meter according to standard samples No. 1395-78 and No. 1412-78 of the GSOue set.

If the measurement range of the meter being verified is less than the range from 14 to 37 MS/m or the meter has several subranges, the adjustment should be carried out using standard samples of the GSOue set that have electrical conductivity values ​​closest to the boundaries of the range (subranges).

The main error is determined over the entire range (subranges) of specific electrical conductivity values ​​at at least three points evenly spaced in the range (subranges), one of which must be in the middle of the verified range (subrange), excluding the meter adjustment points.

To determine the main error, it is necessary to sequentially install the ETP of the meter being verified on the surface of selected standard samples, and carry out at least 5 measurements at each point. Record the meter readings in the verification report in the table of observation results.

Based on the meter readings, calculate the arithmetic mean value taken as the result of measuring the electrical conductivity, using the formula:

where s i- meter reading;

n- number of measurements.

The main relative error of the meters being verified is determined by the formula:

Where? - basic relative error;

s is the actual value of the specific electrical conductivity of the standard sample of the GSOue set;

- the result of measuring the electrical conductivity of a given standard sample.

The main relative error of the meter should not exceed the value specified in the documentation for it.

If measurements are performed according to OST 1 92070.0-78, the main relative error should not exceed ± 2%.

4.3.1.2. Determination of the main error of meters that have a pointer device with a uniform division scale as an indicator device, not calibrated in units of electrical conductivity, is carried out as follows:

Set up the meter to be verified according to standard samples No. 1395-78 and No. 1397-78 (No. 1402-78 and No. 1404-78 or No. 1410-78 and No. 1412-78) of the GSOue set so that the dial indicator is within the dial indicator scale calibrated meter;

Calculate the price of division of the dial indicator scale using the formula:

Where? - the price of division of the dial indicator scale;

s" - actual value of specific electrical conductivity of standard sample No. 1397-78 (No. 1404-78 or No. 1412-78);

s" - actual value of specific electrical conductivity of standard sample No. 1395-78 (No. 1402-78 or No. 1410-78);

Da is the difference in the readings of the pointer indicator of the meter being verified, calculated by the formula:

Da = a" - a" (4)

for dial indicators with a zero mark at the edge of the scale or according to the formula:

Da = a" + a" (5)

for dial indicators with a zero mark in the center of the scale,

where a" is the reading of the dial indicator of the meter being verified when measuring specific electrical conductivity of standard sample No. 1397-78 (No. 1404-78 or No. 1412-78);

a" - readings of the dial indicator of the meter being verified when measuring specific electrical conductivity of standard sample No. 1395-78 (No. 1402-78 or No. 1410-78).

For the convenience of calculations, by correcting the sensitivity of the meter being verified, it is possible to select a certain value of the scale division value of the dial indicator (for example, set one scale division equal to 0.1 MS/m).

Sequentially install the ETP of the meter being verified on the surface of standard samples No. 1396-78, 1403-78 and No. 1411-78 of the GSOue set and record the meter readings in the verification report. At least 5 measurements must be taken at each point.

Based on the meter readings, calculate the observation results using the formulas:

s i= s" + ?Da 1 , (6)

s i= s" + ?Da 2 , (7)

where s i- result of observation;

s", s" - actual values ​​of the specific electrical conductivity of standard samples of the GSOue set used when setting up the meter being verified, with smaller and larger values ​​relative to the point being measured;

Da 1, Da 2 - the difference in the readings of the meter being verified, calculated using the formulas:

Da 1 = a i- a" (8)

Da 2 = a" - a i (9)

for meters with a dial indicator with a zero mark at the edge of the scale and according to the formulas:

Da 1 = a" - a i (10)

Da 2 = a i+ a" (11)

for meters with a dial indicator with a zero mark in the center of the scale,

where a i- readings of the dial indicator of the meter being verified when measuring the specific electrical conductivity of a standard sample, recorded in the verification report;

a", a" - readings of the dial indicator of the meter being verified during setup.

The result of measuring specific electrical conductivity is calculated using formula (1).

The main relative error of the meters being verified is determined by formula (2).

The main relative error of the meter should not exceed the value specified in the documentation for it. If measurements are performed according to OST 1 92070.0-78, the main relative error should not exceed ± 2%.

4.3.2. Determination of the influence of detuning from changes in the gap is carried out for meters that have adjustment of detuning from the gap. For meters with one measurement range, this operation should be carried out on standard sample No. 1403-78 of the GSOue set. For meters with several measurement subranges, this operation must be carried out on one standard sample of the GSOue set, corresponding to the middle of each subrange.

Set up the meter being verified as specified in the requirements of paragraphs. 4.3.1.1 or 4.3.1.2. Detune the meter from changes in the gap in accordance with the technical description for the meter being verified.

Install the VTP of the meter being verified on a standard sample of the GSOUE kit, carry out at least 5 measurements of electrical conductivity and record the meter readings in the verification report.

Place a gap simulator on a standard sample of the GSOue set and repeat the measurements, the results of which are recorded in the verification report.

Based on the meter readings, calculate the measurement results of the electrical conductivity of a standard sample of the GSOue set without gap s0 and with a gap simulator s3, as specified in the requirements of paragraphs. 4.3.1.1 and 4.3.1.2.

The relative difference between the measurement results is calculated using the formula:

and should not exceed 2%.

4.3.3. Determination of the influence of the edge effect when measuring electrical conductivity is carried out on standard sample No. 1.

The settings of the meters being verified, which have a digital display board or a pointer device calibrated in units of electrical conductivity as an indicator device, must be carried out on standard samples of the GSOue set in accordance with the technical documentation for the meter.

The adjustment of meters being verified, having as an indicator device a pointer device with a uniform scale of divisions, not calibrated in units of specific electrical conductivity, must be carried out in accordance with the requirements of clause 4.3.1.2 on standard samples of the GSOue set, having values ​​of specific electrical conductivity closest to the preliminary measured value of electrical conductivity of standard sample No. 1.

Install the ETP of the meter being verified in the central zone of standard sample No. 1 and measure its electrical conductivity. Record the results of 5 observations in the verification report.

Consistently, installing the ETP of the meter being verified at a minimum distance from the edge of standard sample No. 1 in two mutually perpendicular directions, as indicated in reference Appendix 2, take 3 measurements at each point. Record the observation results in the verification protocol.

Calculate the results of measurements of the electrical conductivity of standard sample No. 1 in the center and in the edge zones using the formulas given in paragraphs. 4.3.1.1 or 4.3.1.2.

To in the center and at the minimum permissible distance from the edge of standard sample No. 1 according to the formula:

where s And- the result of measuring the electrical conductivity in the center of standard sample No. 1;

s To- the result of measuring the electrical conductivity at the edge of standard sample No. 1.

The maximum relative difference in the measurement of electrical conductivity in the center and at the edge of the sample should not exceed ± 1%.

4.3.4. Determination of the influence of product thickness when measuring specific electrical conductivity is carried out on standard sample No. 2.

The settings of the meters being verified must be carried out in accordance with the requirements of clause 4.3.3.

Install the ETC of the meter being verified in the center of a section with a smaller thickness and measure its electrical conductivity. Record the results of 5 observations in the verification report. Then measure the electrical conductivity of a section of a standard sample of greater thickness, similar to that indicated above.

Calculate the results of measurements of the electrical conductivity of standard sample No. 2 in sections of various thicknesses in accordance with the requirements of paragraphs. 4.3.1.1 and 4.3.1.2.

Calculate relative difference of electrical conductivity measurement? T in areas of varying thickness according to the formula:

where s" T- the result of measuring the electrical conductivity of a section of standard sample No. 2 with a smaller thickness;

s" T- the result of measuring the electrical conductivity of a section of standard sample No. 2 with greater thickness.

The relative difference in the measurement of specific electrical conductivity of standard sample No. 2 in areas of different thicknesses should not exceed ± 1%.

4.3.5. Determination of the influence of product surface roughness is carried out on standard sample No. 3.

The settings of the meters being verified must be carried out in accordance with clause 4.3.3.

Install the VTP of the meter being verified in the central zone of standard sample No. 3 on a surface characterized by roughness Rz 1, and carry out 5 measurements of electrical conductivity. Record the observation results in the verification protocol.

Similarly, measure the electrical conductivity of standard sample No. 3 from the side of the surface with roughness Rz 2 .

Calculate the results of measurements of the electrical conductivity of standard sample No. 3 in areas with different roughness in accordance with the requirements of paragraphs. 4.3.1.1 and 4.3.1.2.

Calculate relative difference of electrical conductivity measurement? R standard sample No. 3 in areas with different roughness according to the formula:

where s" R Rz 1 ;

s" R- the result of measuring the electrical conductivity of standard sample No. 3 in the area with roughness Rz 2 .

The relative difference in measuring the electrical conductivity of standard sample No. 3 in areas with different roughness should not exceed ± 1%.

4.3.6. Determination of the VTP parameters of the meter being verified is carried out using a universal bridge of type E7-4 by measuring the active resistance and inductance of the VTP windings.

The measured values ​​of active resistance and inductance of the VTP windings must be within the limits established in the technical documentation for the meter being verified.

5. REGISTRATION OF VERIFICATION RESULTS

5.1. The results of the meter verification must be documented in the protocol given in the recommended Appendix 5.

5.2. Positive verification results should be formalized by recording the results of departmental verification in the operational passport, certified in the prescribed manner, and by applying a verification stamp to the meter being verified.

5.3. It is prohibited to release into circulation and use meters that have been verified with a negative result. In this case, the mark must be canceled and an indication of the unsuitability of the meter must be made in the documents for the meter being verified.

ANNEX 1

Mandatory

CLEARANCE SIMULATOR

*Size for reference.

The gap simulator material is any non-conducting, non-magnetic material.

h and- the thickness of the gap simulator must correspond to the value of the adjusted gap according to the technical description for this type of meter being verified.

Maximum deviations in the thickness of the gap simulator are ± 0.01 mm.

Gap simulators must be metrologically certified based on geometric parameters.

The frequency of checking gap simulators is at least once a year.

APPENDIX 2

Mandatory

STANDARD SAMPLE No. 1

*Size for reference.

The material of standard sample No. 1 is alloy D16 according to GOST 4784-74 in the annealed state.

l- the minimum permissible distance from the edge of the sample to the axis of the winding of the high-voltage transformer (according to the technical description for this type of meter being verified).

Standard sample No. 1 must be metrologically certified in terms of geometric parameters.

Standard sample No. 1 is subject to annual verification.

APPENDIX 3

Mandatory

STANDARD SAMPLE No. 2

*Size for reference.

The material of standard sample No. 2 is alloy D16 according to GOST 4784-74 in the annealed state.

h 1 - the minimum thickness of standard sample No. 2 must correspond to the minimum permissible thickness of the controlled product according to the technical description for this type of meter being verified.

h 2 = 2h 1 .

^ - places of measurement of specific electrical conductivity.

Maximum size deviations h 1 and h 2 ± 0.1 mm.

Standard sample No. 2 must be metrologically certified in terms of geometric parameters.

Standard sample No. 2 is subject to annual verification.

APPENDIX 4

Mandatory

STANDARD SAMPLE No. 3

*Size for reference.

The material of standard sample No. 3 is alloy D16 according to GOST 4784-74 in the annealed state.

Rz 1 - surface roughness parameter A must be equal to the maximum permissible value of the roughness of the controlled surface according to the technical description for this type of meter being verified.

If the required roughness parameter is not specified in the technical description for the meter, the parameter Rz 1 is taken equal to 40 µm.

Standard sample No. 3 must be metrologically certified in terms of geometric parameters.

Standard sample No. 3 is subject to annual verification.

DECOR
verification protocol for eddy current meters of electrical conductivity

PROTOCOL No. ______ verification of eddy current meter of electrical conductivity _________________________________________________________________________ type of meter being verified Head No. _________, subject to _____________________________________________ type of verification owned by _________________________________________________________________ Business name carried out by ______________________________________________________________ name of the enterprise (organization, division), __________________________________________________________________________ who carried out the verification Verification date “____” _________19____ The observation results are given in table. 1.

Table 1 The verification results are given in table. 2. table 2 Conclusion ________________________________________________________________ pass, fail Trustee _______________ “_____” ______________ 19_____

Specific electrical conductivity (electrical conductivity) - quantitative characteristic of water’s ability to conduct electric current.

This ability is directly related to the concentration of ions in water. Conducting ions come from dissolved salts and inorganic materials such as alkalis, chlorides, sulfides and carbonate compounds, etc. The more ions present, the higher the conductivity of water.

Ions conduct electricity due to their positive and negative charges. When substances dissolve in water, they split into positively charged (cationic) and negatively charged (anionic) particles. When solutes are broken down in water, the concentrations of each positive and negative charge remain equal. This means that although the conductivity of water increases with added ions, it remains electrically neutral

In most cases, the specific electrical conductivity of land surface waters is an approximate characteristic of the concentration of inorganic electrolytes in water - Na cations+ , K + , Ca 2+ , Mg 2+ and Clˉ, SO 4 2-, HCO 3 - anions . The presence of other ions, e.g. Fe (II), Fe (III), Mn(II), NO 3 - , HPO 4 2- usually has little effect on the value of electrical conductivity, since these ions are rarely found in water in significant quantities. Hydrogen and hydroxyl ions in the range of their usual concentrations in surface waters of land have practically no effect on the electrical conductivity. The influence of dissolved gases is equally small.

Conductivity can be measured by applying an alternating electrical current (I) to two electrodes immersed in a solution and measuring the resulting voltage (V). During this process, cations migrate to the negative electrode, anions to the positive electrode and the solution acts as an electrical conductor. Voltage is used to measure water resistance, which is then converted to conductivity. Conductivity is the reciprocal of resistance and is measured in the amount of conductivity over a certain distance.

The unit of electrical conductivity is Siemens per 1 m (S/m).For water, derived values ​​are used as a unit of measurement - milliSiemens per 1 m (mS/m) or microSiemens per 1 cm (μS/cm). For very pure water, it is inconvenient to operate with the conductivity value, so the term resistivity, measured in Ohm/m (KOhm/cm or MOhm/cm), is more often used. So, for example, pThe conductivity of rivers can range from 50 to 1500 µS/cm, ddistilled water has a conductivity in the range from 0.5 to 5 µS/cm, ultrapure deionized water 10-18 MOhm/cm.

Conductivity in streams and rivers primarily depends on the geology of the area through which the water flows. Streams flowing through areas with granite rock tend to have lower conductivity because granite is composed of more inert materials that do not ionize (dissolve into ionic components) when washed in water. On the other hand, streams flowing through areas with clay soils tend to be more conductive due to the presence of materials that ionize when flushed in water. Groundwater inflows can have similar effects depending on where they flow through. Discharges to rivers can change conductivity depending on their composition. A faulty sewer system will increase conductivity due to the presence of chloride, phosphate and nitrate; an oil spill will reduce conductivity.

The conductivity of water must be accurately measured using a calibrated device - a conductivity meter. Conductivity is directly affected by the geometric properties of the electrodes; that is, conductivity is inversely proportional to the distance between the electrodes and proportional to the area of ​​the electrodes. This geometric relationship is known as the cell constant. Constant cell and resistance measurement that must be checked and adjusted if necessary.

In addition to the geometric properties of the electrode in the device, and conductivity is also affected by temperature: the warmer the water, the higher the conductivity. For this reason, electrical conductivity is reported as conductivity at 25 degrees Celsius (25 °C).Increasing the temperature of the solution will lead to a decrease in its viscosity and an increase in the mobility of ions in the solution. Increasing the temperature can also lead to an increase in the number of ions in solution due to the dissociation of molecules. Since the conductivity of a solution depends on these factors, increasing the temperature of the solution will lead to an increase in its conductivity. Knowing this dependencemany instruments automatically correct the actual reading to display the value that would theoretically be observed at a nominal temperature of 25°. This is typically done using a temperature sensor built into the conductivity sensor and a software algorithm built into the conductivity meter. However forLinear temperature compensation assumes that the temperature coefficient of variation has the same value for all measured temperatures. This assumption is incorrect; but for many measurements this does not make a significant contribution to the overall measurement uncertainty of the reported result.

http://www.iwinst.org/wp-content/uploads/2012/04/Conductivity-what-is-it.pdf
https://hmc.usp.org/sites/default/files/documents/HMC/GCs-Pdfs/c645.pdf
https://www.google.ru/urlsa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=0ahUKEwjR9Kautv_WAhVFP5oKHRb4D3MQFgg7MAI&url=http%3A%2F%2Fwww.fondriest.com%2Fenvironmental-measurements%2Fparameters%2Fwater-quality%2Fcon ductivity- salinity-tds%2F&usg=AOvVaw31-HAReIg1Tn1CDOmaAVim
The Clean Water Team Guidance Compendium for Watershed Monitoring and Assessment State Water Resources Control Board FS-3.1.3.0(EC)V2e 4/27/2004
https://www.reagecon.com/pdf/technicalpapers/Effect_of_Temperature_TSP-07_Issue3.pdf
RD 52.24.495-2005 Hydrogen index and specific electrical conductivity of water. Methodology for performing measurements using the electrometric method

Usage: in measuring technology in hydrophysical research. The essence of the invention: a seawater electrical conductivity meter contains a sinusoidal signal generator 1, an alternating current source 2, a primary measuring transducer (PMT) 3, two rectifiers 4, 6, a comparator 5, a direct current source 7, two controlled switches 8, 9, a capacitor 10, RS trigger 11, integrator 12, voltage-frequency converter 13, frequency divider 14, recorder 15, distributor 16. The meter automatically balances the rectified output voltage of the primary PIP 3 with the voltage accumulated by the timing capacitor 10, the charging current of which is formed from the generator voltage 1, feeding PIP 3, and the charging time is set as a multiple of the period of the meter’s output frequency. 2 ill.

The invention relates to measuring technology and can be used in hydrophysical studies to measure the specific electrical conductivity of sea water. A known conductometer with a three-electrode cell containing an operational amplifier, a matching transformer with a reference resistor in the secondary winding and a power source. The principle of operation of the conductometer is to automatically balance the currents in the current electrode of the three-electrode cell and in the reference resistor circuit. The amount of current, measured by the voltage drop across the reference resistor, is proportional to the electrical conductivity of the liquid into which the conductometric cell is immersed. The disadvantage of such a conductometer is the low noise immunity of the analog output signal, as well as its dependence on the instability of the amplitude of the alternating voltage of the power source, which reduces the measurement accuracy. A device is known for measuring the specific electrical conductivity of a liquid, containing a series-connected sinusoidal voltage generator, a primary functional transducer and a meter, the second input of the functional transducer is connected to the output of the generator; The functional converter is designed as a two-channel voltage-frequency converter and contains a phase shifter, two comparators, a reference voltage source, a logic block, an integrator, voltage-frequency and frequency-voltage converters. The principle of operation of the device is to balance the durations of 0 and x pulses generated by comparators of their alternating voltages U o and U x coming from the outputs of the generator and primary converter, respectively. The voltage U x is brought into phase with the voltage U 0 using a phase shifter. The reference inputs of the comparators are supplied with voltages from the output of the reference voltage source (U 0) and through the feedback circuit from the output of the frequency-voltage converter (U x). In steady state operation ( 0 =T x), the output frequency of the device is proportional to the measured electrical conductivity. The disadvantage of the known device is the low measurement accuracy due to the presence of a phase shifter in the measuring circuit of the device and the error it introduces in synchronizing the phases of alternating voltages U 0 and U x. The closest to the proposed meter in technical essence and the achieved result is a device for measuring the specific electrical conductivity of sea water, containing a sinusoidal signal generator, the output of which is connected to the primary converter and the input of the reference voltage source, a comparator, the output of which is connected to a series-connected integrator, voltage converter -frequency and recorder; the second input of the comparator is connected to the output of the frequency-voltage converter, the first input of which is connected to the output of the voltage-frequency converter, and the second input to the output of the reference voltage source. The operating principle of the device is to automatically balance the voltages U x and U p supplied to the inputs of the comparator from the outputs of the primary converter and the frequency-voltage converter, respectively. The disadvantage of the known device is the low measurement accuracy due to the nonlinearity of the sinusoid of the generator output voltage and the instability of the reference voltage, and, consequently, the nonlinearity of the dependence of the output voltage U p of the frequency-voltage converter on changes in the amplitude of the generator output voltage. The purpose of the invention is to increase the measurement accuracy by converting the sinusoidal voltage of the generator into the charging current of the timing capacitor. This is achieved by the fact that the meter of the electrical conductivity of sea water, containing a sinusoidal signal generator, a primary measuring transducer, a comparator, a series-connected integrator, a voltage-to-frequency converter and a recorder, additionally includes a series-connected frequency divider, connected by the input to the output of the voltage-to-frequency converter , a pulse distributor and a controlled RS trigger, connected by the output to the input of the integrator, an alternating current source connected by the input to the output of the generator, and by the output to the input of the primary measuring transducer, the output of which is connected through a rectifier to the input of the comparator, connected by the output to the second input of the RS trigger , a second rectifier connected in series with the generator output, a direct current source, the first and second controlled switches and a timing capacitor, the control inputs of the first and second keys are connected respectively to the second and first outputs of the distributor, the third output of which is connected to the third input of the controlled RS- trigger, the fourth output of the distributor is connected to its second input, the second output of the timing capacitor is connected to the combined output of the first switch and the second input of the comparator, the first output of the capacitor is grounded. Achieving this goal is associated with the conversion of the alternating voltage of the generator into the charging current of the timing capacitor, the charging time of which, by means of frequency correction of the voltage-frequency converter, is set to a multiple of the output frequency period; the voltage accumulated by the capacitor compensates for the pre-rectified output voltage of the primary measuring transducer. In fig. 1 shows a block diagram of the proposed meter; in fig. 2 signal timing diagrams explaining the operation of the meter. The meter of electrical conductivity of sea water contains a series-connected sinusoidal signal generator 1, an alternating current source 2, a primary measuring transducer (PMT) 3, a rectifier 4 and a comparator 5, a series-connected second rectifier 6 connected by the input to the output of the generator 1, a constant source 7 current, controlled switches 8, 9 and a timing capacitor 10, connected by the second output to the combined output of the key 8 and the second input of the comparator 5, the first output of the capacitor 10 is grounded, series-connected controlled RS trigger 11, integrator 12, voltage-to-frequency converter 13, divider 14 frequencies, combined by an input with the input of the recorder 15, and a pulse distributor 16, connected by the first output to the R-input of the trigger 11, the second S-input of which is connected to the output of the comparator 5, the second control inputs of the keys 8 and 9 are connected to the second and first outputs, respectively distributor 16, the third output of which is connected to the third input of trigger 11, the fourth output of the distributor is connected to its second R-input. The meter works as follows. The sinusoidal voltage U g of generator 1 is converted by source 2 into an amplitude-stabilized alternating current I I, feeding the three-electrode cell of PIP 3: I I U g /R t2, where R T2 is the resistance of the current-setting resistor of source 2. At the output of PIP 3, a sinusoidal voltage curve 17 is formed. (in Fig. 2), the amplitude of which is inversely proportional to the specific electrical conductivity of sea water into which PIP 3 is immersed. Rectifier 4 converts the alternating voltage from the output of PIP 3 into a direct voltage U supplied to the first input of comparator 5:

Where K 4 is the conversion coefficient of the rectifier 4. At the second input of the comparator 5, a compensation voltage is formed, accumulated by the timing capacitor 10 during the duration pi of the output pulse of the distributor 16. The output pulses of the converter 13 (diagram 18 in Fig. 2), following with a frequency f through divider 14, which reduces the frequency by K 14 times, is supplied to the C-input of distributor 16 (diagram 19 in Fig. 2), the pulses at outputs 1-4 of which are presented in diagrams 20-23 in Fig. 2. The duration pi of the pulses at outputs 1-3 of the distributor 16 is determined by the following expression: pi = . During the pulse duration pi (diagram 21 in Fig. 2) from the second output of the distributor 16, supplied to the control V-input of the switch 8, the timing capacitor 10 is charged (diagram 24, Fig. 2) from the direct current source 7, controlled through the rectifier 6 sinusoidal voltage U g of generator 1. The charge current of capacitor 10 is determined by the following expression: I 3 = , where K 6 is the conversion coefficient of rectifier 6, R t7 is the resistance of the current-setting resistor of source 7. The voltage U c on the capacitor plates is determined by the charging time, charge current I c and capacitance C: U c = The maximum voltage value U cmax to which the capacitor 10 can be charged is determined by the duration pi: U c max = At ​​the end of the pulse duration 21, the charging of the capacitor 10 stops, and with the beginning of the next cycle of operation of the distributor 16 during the pulse duration (diagram 20 in Fig. 2) from its first output, which opens the key 8, the capacitor 10 is discharged (diagram 28 in Fig. 2). Comparator 5, comparing the voltages U c and U supplied to its inputs, is triggered (diagram 24 in Fig. 2) if their equality is achieved during the duration of pulse 21 (see Fig. 2), i.e. h< < ри. Выходной импульс компаратора 5 (диаграмма 25 на фиг. 2) устанавливает триггер 11 в состояние лог. "1", которое действует на его выходе (диаграмма 26 на фиг. 2) в течение длительности импульса (диаграмма 22 на фиг. 2) с третьего выхода распределителя 16, поступающего на вход 3 управления триггера 11. Состояние лог. "1" на выходе триггера 11 вызывает увеличение выходного напряжения интегратора 12 (диаграмма 27, фиг. 2), что приводит к увеличению частоты f выходных импульсов генератора 13, а следовательно, к уменьшению длительности ри импульса (диаграмма 21, фиг. 2) распределителя 16, т.е. к выравниванию длительностей з и ри ( ри _ з). Если же электрическая проводимость морской воды такова, что напряжение U остается недосягаемым для напряжения U c в течение длительности ри (диаграмма 28, фиг. 2), сигнал на выходе компаратора 5 будет отсутствовать. Сигнал лог. "0", действующий при этом на выходе триггера 11, вызовет уменьшение выходного напряжения (диаграмма 29 на фиг. 2) интегратора 12. Частота f преобразователя 13 уменьшится, длительность ри возрастет, создавая возможность достижения равенства U U c в течение длительности ри. Таким образом, в течение нескольких циклов работы распределителя 16 наступит установившийся режим, характеризующийся условием з ри, т.е. достижением равенства напряжений U (1) (4) выходная частота преобразователя пропорциональна удельной электропроводимости морской воды. Предлагаемый измеритель имеет меньшую погрешность, а также более простую схему и высокую надежность. Лабораторные испытания подтверждают снижение относительной основной погрешности на 0,02% по сравнению с прототипом.

CLAIM

SEA WATER SPECIFIC ELECTRICAL CONDUCTIVITY METER, containing a sinusoidal signal generator, a primary measuring transducer, a comparator, a series-connected integrator, a voltage-to-frequency converter and a recorder, characterized in that, in order to increase the measurement accuracy, a series-connected frequency divider is additionally introduced into it input to the output of the voltage-to-frequency converter, a pulse distributor and a controlled RS trigger, connected by the output to the input of the integrator, an alternating current source connected by the input to the output of the generator, and the output to the input of the primary measuring transducer, the output of which is connected through a rectifier to the first input of the comparator , connected by the output to the S-input of the RS trigger, a second rectifier connected in series, connected by the input to the output of the generator, a direct current source, the first and second controlled switches and a timing capacitor, the other output of which, connected to the output of the second switch, is connected to a common power bus , the control inputs of the first and second switches are connected respectively to the second and first outputs of the distributor, the third output of which is connected to the third input of the controlled RS flip-flop, the fourth output of the distributor is connected to its second input, the second output of the timing capacitor is connected to the combined output of the first switch and the second input comparator.

Electrical conductivity is the ability of substances to conduct electric current under the influence of an external electric field. Electrical conductivity is the reciprocal of electrical resistance L = 1/ R.

Where ρ – resistivity, Ohm m; - specific electrical conductivity, S/m (Siemens/meter); S– cross section, m2; l – conductor length, m) ( in electrochemistry, specific electrical conductivity ( ) read - kappa).

The unit of measurement L is Siemens (Sm), 1 Sm = 1 Ohm -1.

Electrical conductivity solution characterizes the conductivity of a volume of solution enclosed between two parallel electrodes having an area of ​​1 m 2 and located at a distance of 1 m from each other. The SI unit of measurement is Sm m -1.

The specific conductivity of an electrolyte solution is determined by the number of ions that carry electricity and the rate of their migration:

, (2.5)

Where α – degree of electrolyte dissociation; WITH– molar concentration of equivalent, mol/m3; F – Faraday number, 96485 C/mol;
- absolute velocities of movement of the cation and anion (velocities with a field potential gradient equal to 1 V/m); The unit of measurement for speed is m 2 V -1 s -1.

From equation (2.5) it follows that depends on the concentration for both strong and weak electrolytes (Figure 2.1):

Figure 2.1 – Dependence of specific electrical conductivity on the concentration of electrolytes in aqueous solutions

In dilute solutions at C → 0 tends to the specific electrical conductivity of water, which is about 10 -6 S/m and is due to the presence of ions N 3 ABOUT + And HE - . With increasing electrolyte concentration, initially increases, which corresponds to an increase in the number of ions in the solution. However, the more ions in a solution of strong electrolytes, the stronger the ionic interaction, leading to a decrease in the speed of ion movement. For weak electrolytes in concentrated solutions, the degree of dissociation and, consequently, the number of ions carrying electricity are noticeably reduced. Therefore, almost always, the dependence of specific electrical conductivity on electrolyte concentration passes through a maximum.

2.1.3 Molar and equivalent electrical conductivities

To highlight the effects of ionic interaction, electrical conductivity divided by the molar concentration (C, mol/m3), and get molar electrical conductivity ; or divide by the molar concentration of the equivalent and get equivalent conductivity.

. (2.6)

Unit of measurement is m 2 S/mol. The physical meaning of equivalent conductivity is as follows: the equivalent conductivity is numerically equal to the electrical conductivity of a solution enclosed between two parallel electrodes located at a distance of 1 m and having such an area that the volume of the solution between the electrodes contains one mole of equivalent solute (in the case of molar electrical conductivity - one mole of solute). Thus, in the case of equivalent electrical conductivity in this volume there will be N A positive and N A negative charges for a solution of any electrolyte, provided that it is completely dissociated (N A is Avogadro’s number). Therefore, if the ions did not interact with each other, then would remain constant at all concentrations. In real systems depends on the concentration (Figure 2.2). When C → 0,
→ 1, value strives for
, corresponding to the absence of ionic interaction. From equations (2.5 and 2.6) it follows:

Work
called limiting equivalent electrical conductivity of ions, or ultimate mobility ions:

. (2.9)

Relation (2.9) was established by Kohlrausch and is called law of independent movement of ions . The maximum mobility is a specific value for a given type of ion and depends only on the nature of the solvent and temperature. The equation for molar electrical conductivity takes the form (2.10):

, (2.10)

Where
- the number of equivalents of cations and anions required to form 1 mole of salt.

Example:

In the case of a monovalent electrolyte, such as HCl,
, that is, the molar and equivalent electrical conductivities are the same.

Figure 2.2 – Dependence of equivalent electrical conductivity on concentration for strong (a) and weak (b) electrolytes

For solutions of weak electrolytes, the equivalent electrical conductivity remains small down to very low concentrations, upon reaching which it rises sharply to values ​​comparable to strong electrolytes. This occurs due to an increase in the degree of dissociation, which, according to the classical theory of electrolytic dissociation, increases with dilution and, in the limit, tends to unity.

The degree of dissociation can be expressed by dividing equation (2.7) by (2.8):

.

With increasing concentration solutions of strong electrolytes decreases, but only slightly. Kohlrausch showed that of such solutions at low concentrations obeys the equation:

, (2.11)

Where A– constant, depending on the nature of the solvent, temperature and valence type of electrolyte.

According to the Debye–Onsager theory, a decrease in the equivalent electrical conductivity of solutions of strong electrolytes is associated with a decrease in the velocities of ion movement due to two effects of inhibition of ion movement, arising due to electrostatic interaction between an ion and its ionic atmosphere. Each ion tends to surround itself with ions of opposite charge. The charge cloud is called ionic atmosphere, on average it is spherically symmetrical.

The first effect is the effect electrophoretic inhibition. When an electric field is applied, the ion moves in one direction, and its ionic atmosphere moves in the opposite direction. But with the ionic atmosphere, due to the hydration of atmospheric ions, part of the solvent is entrained, and the central ion, when moving, encounters a flow of solvent moving in the opposite direction, which creates additional viscous drag on the ion.

Second effect - relaxation inhibition. When an ion moves in an external field, the atmosphere should disappear behind the ion and form in front of it. Both of these processes do not occur instantly. Therefore, in front of the ion the number of ions of the opposite sign is less than behind it, that is, the cloud becomes asymmetrical, the center of the charge of the atmosphere moves back, and since the charges of the ion and the atmosphere are opposite, the movement of the ion slows down. The forces of relaxation and electrophoretic inhibition are determined by the ionic strength of the solution, the nature of the solvent and temperature. For the same electrolyte, under other constant conditions, these forces increase with increasing solution concentration.

Used to measure the electrical conductivity of products made of non-ferromagnetic metals and their alloys. The device was made in Russia, entered into the state register of the Russian Federation (description of the type of measuring instrument). Warranty - 1 year. The small dimensions of the device, as well as the ability to quickly determine electrical conductivity, allow the device to be used for the following purposes:

• acceptance of parts from suppliers with determination of compliance with the brand of material of the products, even under the paint coating;
• prompt sorting of workpieces by grade of materials, using the corresponding tables of electrical conductivity values ​​of various aluminum alloys, bronze, copper alloys, titanium alloys, and so on;
• determining the compliance of the grades of materials of various parts with the required grades according to regulatory documentation during the inspection of products and objects;
• control over the technical process of hardening materials (aluminum and other alloys). Using the tables of correspondence between the degree of hardening and electrical conductivity of a given grade of material, one can clearly determine that the part is under- or over-heated;
• determination of changes in the strength properties of product parts as a result of thermal shock by determining changes in the electrical conductivity of the part material.

The distinctive features of the Constant K6 conductivity meter include the following:

• operation over the entire operating range with one FD2 converter (PF-IE-6e);
• detuning from the influence of the gap between the converter and the test object allows you to measure electrical conductivity through paint coatings of variable thickness;
• small dimensions, convenience and ease of operation;
• a wide range of converters allows you to solve most problems of measuring electrical conductivity;
• the ability to save test results in the device’s memory with subsequent transfer to a PC via USB for storage, statistical processing and documentation using the Constanta-Data program.

The technical characteristics declared by the manufacturer of the electrical conductivity meter Constant K6 are given in the table >

Characteristic	Index
Electrical conductivity measurement range, σ, MS/m*	0.005 ÷ 59
Diameter of the converter control zone, mm	4-6
Indication	matrix LCD indicator displaying the signal and alarm threshold
Number of memory cells of inspection results	999 with the ability to split into 99 groups
Power supply: rechargeable batteries or Alkaline batteries, type AAA	2 pcs.
Continuous operation time, h	50
Operating temperature range	-20...+50°С
Overall dimensions of the electronic unit, mm	120x60x25
Weight, g	150

* The metrological characteristics of the electrical conductivity meter Constant K6 are determined by the type of connected converter.

Technical characteristics of converters for the electrical conductivity meter Constant K6 are given in the following table

Type	Purpose	Electrical conductivity measurement range σ, MS/m	Limit of main relative measurement error,%	Gap adjustment range, mm	Minimum thickness of the test object, mm	Diameter of control zone, mm	Excitation type frequency, kHz
FD2 (PF-IE-6e)	Universal converter. The measurement range covers all possible electrical conductivities of metals and alloys. The gap adjustment is optimized for work on aluminum alloys. Shielded sensitive element with a control zone diameter of 6 mm.	0,5-59	3*	0-0,2	1-5	6	20
PF-IEAv-6e		7-40	3	0-0,2	0,6-1,5	6	60
PF-IE-6e-Ti	Specialized converter. The converter is intended for use in the aviation industry. The increased frequency of eddy current excitation makes it possible to control thin sheet materials made of aluminum alloys.	0,5-5	3	0-0,2	1-2,3	6	170
PF-IE-6e-Br		2-16	3	0-0,2	0,9-2,0	6	60
PF-IE-6e-Cu		25-59	3	0-0,2	1,5-2,0	6	7
PF-IE-4-Ti	Converter for testing small and thin products. The cone-shaped sensing element allows you to measure electrical conductivity on products of complex shapes. The diameter of the control zone is 4 mm. Equipped with a replaceable protective cap.	0,5-5	2	0-0,1	0,3-1,0	4	1800
PF-IE-4-Br		2-16	2	0-0,1	0,3-0,8	4	1200
PF-IE-4-Al		7-40	2	0-0,1	0,3-0,8	4	480
PF-IE-4-Cu		25-59	2	0-0,1	0,5-0,8	4	120
PF-IE-30-U1	The converter for monitoring coals and carbon-graphites is designed to measure the electrical conductivity or electrical resistivity of carbon-graphite materials (CGM) with a rough surface, heterogeneous and porous structure, for sorting coals, carbon-graphites, nipples, electrodes and their cinders.	0,01-1	10**	0-0,5	15	30	70
PF-IE-18e-U2	The converter for testing carbon plastics and carbon-carbon composite materials is designed to measure the electrical conductivity of non-woven and woven carbon composite materials with a binder of polymer resins, as well as with a carbon binder.	0,005-0,1	10***	0-0,5	4	18	3700

* - 3% in the range from 5 to 59 MSm/m, 7% in the range from 0.5 to 5 MSm/m
** – 10% in the range from 0.1 to 1 MSm/m, 15% in the range from 0.01 to 0.1 MSm/m
*** – 10% in the range from 0.005 to 0.02 MSm/m, 15% in the range from 0.02 to 0.1 MSm/m

Delivery kit for electrical conductivity meter Constant K6

• electronic unit with one converter to choose from,
• replaceable protective caps (if provided for by the design),
• AAA batteries (4 pcs.),
• Charger,
• communication cable with PC via USB interface,
• CD with drivers and Constanta-Data program,
• manual,
• verification method,
• case for storage and transportation.

As test standards, the Constant K6 electrical conductivity meter can be equipped with samples of electrical conductivity CO-220 or CO-230. Sets of measures are intended for verification and calibration of meters of electrical conductivity of non-ferrous metals and alloys.

Nominal value of electrical conductivity σ	Titanium group sample set	Set of bronze group samples	Aluminum group sample set	Copper Group Sample Set
Photos of samples
Sample No. 1	0.5 MSm/m	3.5 MSm/m	14 MSm/m	40 MSm/m
Sample No. 2	1 MSm/m	5 MSm/m	17 MSm/m	50 MSm/m
Sample No. 3	2 MSm/m	10 MSm/m	24 MSm/m	58 MSm/m
Thickness of electrical conductivity samples	6 mm
Diameter of electrical conductivity samples	24 mm
Surface roughness of electrical conductivity samples	No more than Ra 1.6 µm
Overall dimensions of the sample set	130 x 48 x 9 mm

The Constant K6 electrical conductivity meter can be purchased with delivery to your door or to the terminals of a transport company in the following cities: Moscow, St. Petersburg, Yekaterinburg, Saratov. Amursk, Angarsk, Arkhangelsk, Astrakhan, Barnaul, Belgorod, Biysk, Bryansk, Voronezh, Veliky Novgorod, Vladivostok, Vladikavkaz, Vladimir, Volgograd, Volgodonsk, Vologda, Ivanovo, Izhevsk, Yoshkar-Ola, Kazan, Kaliningrad, Kaluga, Kemerovo, Kirov , Kostroma, Krasnodar, Krasnoyarsk, Kursk, Lipetsk, Magadan, Magnitogorsk, Murmansk, Murom, Naberezhnye Chelny, Nalchik, Novokuznetsk, Naryan-Mar, Novorossiysk, Novosibirsk, Neftekamsk, Nefteyugansk, Novocherkassk, Nizhnekamsk, Norilsk, Nizhny Novgorod, Obninsk, Omsk , Orel, Orenburg, Okha, Penza, Perm, Petrozavodsk, Petropavlovsk-Kamchatsky, Pskov, Rzhev, Rostov, Ryazan, Samara, Saransk, Smolensk, Sochi, Syktyvkar, Taganrog, Tambov, Tver, Tobolsk, Tolyatti, Tomsk, Tula, Tyumen , Ulyanovsk, Ufa, Khanty-Mansiysk, Cheboksary, Chelyabinsk, Cherepovets, Elista, Yaroslavl and other cities, also in the Republic of Crimea. As well as the Republic of Kazakhstan, Belarus and other CIS countries.