JJG 757-2007 Verification Procedure for Ion Meters JJG757-2007 Standard download decompression password: www.bzxz.net
This procedure applies to the initial verification, subsequent verification and in-use inspection of general-purpose ion meters and special-purpose ion meters that use electrode potential method to determine ion activity. The relevant metrological performance tests in the type evaluation and prototype test of ion meters can also refer to this procedure.

National Metrology Verification Regulation of the People's Republic of China JJG757—2007
Ionometers
Ionometers
2007 - 11 - 21 Issued
Implementation on 2008 05 - 21
Promulgated by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China JIG757—2007
Verification Regulation of Ionometers
Verification Regulation of Ionometers JIG 757—2007
Replaces JJG 757—1991
JJG822—1993
This regulation was approved by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China on November 21, 2007, and came into effect on May 21, 2008.
Responsible unit: National Technical Committee for Physical and Chemical Metrology Drafting unit: China Testing Technology Research Institute This regulation is entrusted to the National Technical Committee for Physical and Chemical Metrology to be responsible for the interpretation of this regulation. Main drafters:
JJG 757--2007
He Qiu (China Testing Technology Research Institute)
Huang Gansheng (China Testing Technology Research Institute)
Article Drafting:
Yuan Li (China Testing Technology Research Institute)
Chen Yu (China Testing Technology Research Institute)
Ni Dezhi (China Testing Technology Research Institute)
3 Metrological performance requirements
3.1 Accuracy grade
3.2 Indication error
3.3 Repeatability...·
Input current·
Input impedance
Temperature compensator error.
Temperature measurement error·
Output error Poor··
Stability·
Supply voltage adaptability
4 General technical requirements.
Appearance and preliminary inspection
Slope regulator adjustment range-
Equipotential regulator adjustment range
4.4 Positioning regulator adjustment range-
Insulation resistance·
5 Measuring instrument control·
Verification conditions
Verification items
Verification methods·
5.4 Processing of verification results
Verification cycle
(0100)ck, value.-
Appendix A (
Appendix B (0-100)2 Appendix ℃
Comparison table of input potential and activity indication
Appendix D Comparison table of input potential and Na* concentration (activity coefficient = 1) Appendix E Original record format of ion meter calibration
Appendix F Two formats in the calibration certificate (first calibration) Appendix G
Format inside the calibration result notice
(3)
(3)
1 Scope
JJG 757—2007
Verification Procedure for Ion Meters
This procedure is applicable to the initial verification, subsequent verification and in-use inspection of general-purpose ion meters and special-purpose ion meters that use the electrode potential method to determine ion activity. The metrological performance tests in the type evaluation and prototype test of ion meters can also be carried out in accordance with this procedure.
2 Overview
The ion meter is an instrument for measuring the ion activity in the solution. It is a high-impedance DC potential measuring instrument. The ion meter measures the ion activity in the solution by measuring the electromotive force of the battery composed of the solution, ion selective electrode and reference electrode. The relationship between the electromotive force of the battery and the ion activity in the measured solution is: E = E\ ± 2.302 6RTJ
Where: E\—starting potential: It includes the "zero potential" of the ion electrode, the reference electrode potential and the liquid junction potential, etc., V;
R——gas constant, 8.3145J·K-1-mol T----thermodynamic temperature, (273.15+t)K—Faraday constant, 9.6485×10*Cmol-1; F
ion valence:
ion activity
2.3026 is called the theoretical slope of the electrode potential, represented by k. Then the formula (1) is E=E\ ± igα*, when F
the measured ion is a positive ion, it is preceded by "_\: when the measured ion is a negative ion, it is preceded by "+". If one is represented by x, then
E = E\ ±kpx
the starting potential E\ is eliminated after adjustment by the standard solution and the ion meter to obtain px=+
if X is antilogarithmically converted and then multiplied by the molar mass of the measured ion, the ion activity can be obtained: Q = 10-XM,
where: M is the molar mass of the measured ion, gmol the relationship between ion activity and concentration is:
a, =febzxz.net
where:
ion activity;
——activity coefficient:
ion liquid degree.
JJG 757-—2007
When, is a constant, the concentration of the measured ion in the solution can be calculated. Metrological performance requirements
3.1 Accuracy level
The instrument accuracy level is divided into 0.2, 0.1, 0.05, 0.02, 0.01 and 0.001 according to the meter performance of the ion meter.
3.2 Indication error
The maximum allowable error of the indication should not be greater than the requirements of Table 1. 3.3 Repeatability
The repeatability of the indication should not be greater than the requirements of Table 1.
3.4 ​​Input current
The input current should not be greater than the requirements of Table 1.
3.5 Input impedance
The input impedance should not be less than the requirements of Table 1.
3.6 Temperature compensator error
At any compensation temperature, when the potential value equivalent to 3PX at that temperature is input, the maximum allowable error of the temperature compensator is The allowable error should not be greater than the requirements of Table 1.
3.7 Temperature measurement error
For ion meters with temperature sensors, the maximum allowable error of temperature indication should not be greater than the requirements of Table 1. 3.8 Output error
For ion meters with analog electrical output, the output current or voltage error should not be greater than the requirements of Table 1. 3.9 Stability
When the power supply voltage remains unchanged, the zero point and indication change within 1h should not be greater than 1 requirement. 3.10 Power supply voltage adaptability
When the power supply voltage changes within (220±22)V, the zero point and indication change should not be greater than the requirements of Table 1. Metrology performance, technical requirements
Instrument level
Division value or minimum maximum indication (px)
pX, (px)
Repeatability
pxn (nx)
nX(px)
Input current/A
±1%FS
10×10
:1)×10-2
5×10~12
12×10~ 12
±0.03%FS
1×1012
Input impedance/n
Temperature compensator
Maximum allowable error
px,(px)
px, (px)
Stability (pX)
Supply voltage adaptability (pXx')
Temperature measurement error/C
Slope adjustment range
Equipotential regulator
Adjustment range (x)
Positioning regulator
Adjustment range (PX)
Output error/% FS
JJG 757--2007
Table 1 (continued)
0.3×1012
1×1012
0.3×1012
Or the indicators given in the manual
Should exceed 80% ~~ 100%:
General ion meters should exceed ±5, and special ion meters should exceed 3. General ion meters should exceed ±5, and special ion meters should exceed 3+1.
Note: 1 Logarithmic display instruments are allowed to add or subtract 1 character from the table value; 2 Items with "*" are secondary items.
4 General technical requirements
4.1 Appearance and preliminary inspection
3×10/2
4.1.1 The instrument should have a nameplate indicating the product name, model, specification, manufacturer name, manufacturing date, factory number and instrument accuracy grade. Domestic ion meters manufactured after May 1, 2006 should have a mark indicating the manufacturer's license and license number.
4.1.2 The appearance and structure of the instrument should be intact, each regulator should be able to adjust normally, and each coagulation piece should not be loose. 4.1.3 The electrode socket should be intact, clean and dry. The connection wires should be firmly connected without any looseness. 4.1.4 The surface markings should be clear and even. The digital display should be clear and complete. 4.1.5 For pointer instruments, the pointer should be straight and should not be stuck or shaken. 4.2 Slope regulator adjustment range
The slope regulator adjustment range should meet the corresponding requirements of Table 1. 4.3 Equipotential regulator adjustment range
The equipotential regulator adjustment range should meet the corresponding requirements of Table 1, 4.4 Positioning regulator adjustment range
The positioning regulator adjustment range should meet the corresponding requirements of Table 1. 4.5 Insulation resistance
The insulation resistance of the power phase and neutral line to the ground (casing) should not be less than 20M2. 5 Measuring instrument control
Measuring instrument control includes initial verification, subsequent verification and in-use inspection. 3
5.1 Verification conditions
JJG 757—2007
5.1.1 The verification environment conditions should meet the requirements of Table 2. Table 2 Calibration environmental conditions
Instrument level
0.01: 0.02
0.05: 0.1; 0.2
5.1.2 Calibration equipment
17 --23
Relative humidity/%RH
Interference factors
No strong mechanical vibration and electromagnetic interference nearby, no corrosive gas in the air. The AC power supply voltage should be stable, the rate is (50±0.5)Hz
51.2.1 The accuracy of DC potentiometer, standard battery and galvanometer matched with potentiometer, or DC standard potential generator such as special calibration instrument should be 3 times higher than the accuracy of the ion meter to be tested. 5.1.2.2 One resistor of 1×10°0.±10%; one resistor of 3×10°0,±10% or 10×10°0,±10%. The resistor should be well shielded.
5.1.2.3 One switch with insulation resistance higher than 0.1×1015n, corresponding high insulation connectors, shielded wires, etc. 5.1.2.4 One digital multimeter, with a range of not less than 2V, a minimum resolution of DC voltage better than 10μV, and an expanded uncertainty (=2) better than 0.03%, a minimum resolution of current better than 0.1mA, and an expanded uncertainty better than 0.1%, (=2).
5.1.2.5 Temperature sensor simulation device (standard resistance box: 0.010~10k2, expanded uncertainty (k-2) better than 0.1%: DC voltage: 0.01mV~1V, expanded uncertainty (=2) better than 0.05%). 5.1.2.6 Precision temperature water tank, temperature control range (0～100)℃, stability better than 0.1℃. 5.1.2.7 Standard thermometer, measurement range (0100)℃, measurement error no more than 0.1℃. 5.1.2.8 One AC voltage stabilizer and one voltage regulator with a capacity 10 times greater than the power consumption of the instrument under test and a stability better than 1%.
5.1.2.9 One 500V megohmmeter, 10th grade. 5.1.2.10 (45-55)Hz, 0.5th grade frequency meter - one. 5.2 Verification items
Verification items are shown in Table 3.
3 Standard items
Inspection items
Appearance and preliminary inspection
Indication error
Repeatability
Input current
Input impedance
Filter compensator error
Drinking test
Subsequent inspection
Inspection during use
Note: 1
Inspection items
Stability
Supply voltage adaptability
Output error
Slope regulator range
JJG 737—2007
Capsule 3 (continued)
First calibration
Adjustment range of equipotential regulator
Adjustment range of positioning regulator
Insulation resistance
“+” indicates items to be inspected, “_” indicates items that may not be inspected. 2 Items marked with “*” are minor items.
Calibration method
Preheat the instrument according to the instructions for use before calibration. Connect the circuit according to Figure 1 for calibration.
5.3.2 Appearance and preliminary inspection
Ion meter
Figure Calibration circuit connection diagram
Inspect by visual inspection and touch according to the requirements of 4.1.5.3.3 Indication error
5.3.3.1 Potential indication
Subsequent calibration
Inspection during use
Digital multimeter
Temperature sensor
Simulation device
The calibration point interval is 100mV; for instruments with a minimum scale of ≤2mV, one point should be calibrated every 20mV in the range of (0～100)mV and 100mV near the upper and lower limits of measurement: for instruments with a minimum scale of 0.1mV, one point should be calibrated every 2.0mV in the range of (0.010.0)mV. Set the ion meter to the potential measurement function, short-circuit the series resistor at the input end, input the zero potential value to the ion meter, and adjust the zero point of the ion meter. Use the method of increasing and decreasing the input potential to input the corresponding potential value of each calibration point. Calculate the potential value error according to formula (5):
Where: E.—
Full-scale potential value, mV
E, - Ep × 100%
JJG 757-—2007
E.——Input potential value at calibration point, mV;
E, average value of indication when increasing and decreasing input, mV. 5.3.3.2pX, indication
The interval of calibration point is 1 pX. For ion meters above 0.01 level, it should also be (0 ~1) pX interval and in the measurement upper limit value to the measurement upper limit minus 1pX interval, calibrate one point at 0.2pX intervals. Set the ion meter to pX, measurement function, temperature compensator to 257, and input end series resistor short circuit. Input zero potential, adjust the ion meter indication to zero potential x value. For ion meters with isopotential regulators, adjust the ion meter isopotential value according to the instrument manual, and then adjust the positioning regulator to make the ion meter indication zero potential value. Set the slope regulator to 100% (for ion meters without slope regulator position, input a potential value equivalent to the interval between the ion meter potential x value and the measurement upper limit pX value. This value is calculated according to formula (6). Adjust the slope regulator to make the ion meter indication the measurement upper limit value. Then input zero potential and adjust the ion meter positioning to zero potential x value). E, = (pXpX,)
Where: E—Standard value of the potential at the calibration point, mV: k—Theoretical slope of the potential of the calibration temperature electrode (see Appendix A), mV/pX: pX—Nominal value of the calibration point, PX;
pX,—zero potential pX value, pX.
Use the method of increasing and decreasing the input potential respectively to input the corresponding potential value of each calibration point. Calculate PX according to formula (7):
pXu = Cheng,- pX1
Where: PX——Average value of the calibration point indication, PX; pxb input value, pX.
5.3.3.3 pX, indication
For ion meters that use analog mode to convert mV to pX, the ion meter should also be set to pX, measurement function, and pX, indication error verification should be carried out in the same way as pX indication verification. The values ​​at different temperatures are shown in Appendix B. 5.3.3.4 Activity indication
The ion meter is set to activity (c,) measurement function, the temperature compensator is set to 25, and the slope compensator is set to 100%: input 59.160mV potential to the ion meter, adjust the digital ion meter indication to 100, and the pointer ion meter indication to 1.00. According to the activity indication range of the ion meter, use the method of increasing and decreasing the input potential to input 10 activity potential values ​​evenly distributed among the potentials listed in Appendix C. Calculate the activity indication error according to formula (8): Cw
Where: c.—indication average value:
Cr=Ch
×100%
c—corresponding theoretical activity indication of input potential (8)
For ion meters that directly display ion activity below, the slope should be calibrated using the two-point method in accordance with the instrument manual, and then the potential values ​​of 0.2, 0.4, 0.6, *, 1.0, 2.0, 3.0 to the maximum value should be input by increasing and decreasing the input potential respectively, and the average value of the activity indication at each point when the input increases and decreases is calculated. Calculate the activity indication error according to formula (9): 6
Average value:
Where: G——
JJG 757-2007
Cm = E × 100%
——Standardized activity value calculated according to input potential and formula 4). Ch
Note: The relationship between Na input potential and concentration (activity) is shown in Appendix Da5.3.3.5c activity value
For ion meters that use analog mode for pX-conversion, the ion meter should also be set to c, measurement function, and the c1 indication should be verified in the same way as the c1 indication. When the c1 indication is verified, if the indication exceeds the above 5.3.3.6 The above indication error is reduced by one year. If the reading cannot be read within the limit, the maximum potential value of the measurement limit can be reduced by 2 to 5. The potential corresponding to the allowable error value is used to determine the upper limit of measurement. 5.3.4 Input current / According to 5.3.3.2, record the ion meter indication. Repeat the current measurement: Where: R-the resistance value of the connected resistor R, the average value of the circuit series resistance × 10-3 10°0, observe and record the input resistance calculated by formula (10). Replace the connected resistor R with a resistor with a larger resistance. If the measurement of high resistance and no high resistance is unchanged, the input current can be calculated. 5.3.5 Input resistance and no series resistance 3, input positive and negative self-ion meter according to 5.3.3., input 1/2 full-scale potential. Take the indicated value V of the negative input 1 000 mV potential value, 2, and the indicated value of the meter still does not change. The result should be determined by taking the most accurate result. It can be determined that 1/3 of the indicated value of the ion meter is used as the mV potential value of the ion meter with a smaller range. When the range is small, follow the instructions). Record the indicated values ​​Vu and VH of the positive and negative inputs of the ion meter at 10″0/1000. Measure the primary and secondary values, and respectively find out the indicated values ​​when there is no series high resistance and when there is series high resistance. Calculate the over-state theory according to formula (11) MENROIAG
Where: -
When there is no resistance, input positive 1000 nV, the average value of the indication is mV; when there is no high resistance in series, input negative 1000mV, the average value of the indication is mV: when there is a high resistance in series, input positive 1000mV, the average value of the indication is mV; when there is a high resistance in series, input negative 1000mV, the average value of the indication is mV. Vh
For ion meters without mV measurement function, the input impedance verification method is: input 0pX to the measurement upper limit minus 1pX, record the indication when there is no high resistance in series and when there is a high resistance in series, repeat the measurement three times, and calculate the arithmetic mean of the indication when there is no high resistance in series and when there is a high resistance in series. Calculate the input impedance according to formula (12):
JJG 757--2007
[px -px,
R,=T成-成岁-aI×R
Where: When px is not connected to a high resistance, the average value of pX measurement is pX; pX. —When px is not connected to a high resistance, the average value of pX measurement is PX; pXu —When a high resistance is connected, the average value of pX measurement is pX; Apx is connected to a high resistance, 0 The average value of px indication, px. (12)
If the indication of the measurement does not change when the high resistance is connected in series or not connected in series, the resistor R can be replaced with a resistor with a larger resistance, and the calibration can be performed again to calculate the input impedance. If the indication of the measurement still does not change when the high resistance is connected in series or not connected in series, it can be determined that the influence of the input impedance of the ion meter is less than 1/3 of the minimum display value, and the input impedance calibration result uses 13 of the minimum display value as the indication change calculation.
For special ion meters that use low internal resistance electrodes for measurement, input impedance and input current are not required. 5.3.6 Repeatability
5.3.6.1 Potential measurement repeatability
The ion meter is equipped with a potential measurement function. A high resistance is connected to the input circuit, a 300mV potential is input to the ion meter, and the ion meter indication is recorded. Repeat the measurement 6 times, and calculate the repeatability of the ion meter potential measurement according to formula (13): Z(E -E)
Where: E, a high impedance state, the first and second measurement indication, mVE—the arithmetic mean of 6 measurement indications: mV. 5.3.6.2pX. Measurement Repeatability
Adjust the ion meter according to 5.3.3.2, insert a high impedance in series into the input circuit, input a potential value equivalent to 6pX units into the ion meter, record the ion meter indication, repeat the measurement 6 times, and calculate the pX measurement repeatability according to formula (14): Spx
Z(pXx -pxx)2
Where: pXx—high impedance state, the first and second measurement indication, pX; pX, the arithmetic mean of 6 measurement indications, pX. 5.3.7 Temperature compensator error
5.3.7.1 Instruments with manual temperature compensation
The ion meter is set to X, the measurement function is set, the temperature compensator is adjusted between its upper and lower limits, and the change in the ion meter indication should conform to its scale (or minimum display) value. Then adjust the temperature compensator to a temperature other than 25 for calibration. The calibration points should be selected from no less than 4 nominal temperature points including the upper and lower end points of the temperature compensator. At each temperature calibration point, the method of increasing and decreasing the input potential is used. Each input is equivalent to the potential of 6X value at that temperature. The average value of the indication when increasing and decreasing the input is calculated. The error of the temperature compensator is calculated according to formula (15): Apx,-6
Where: px——average value of the indication.1 Potential measurement repeatability
The ion meter is set to the potential measurement function. High resistance is input into the circuit, 300mV potential is input into the ion meter, and the ion meter indication is recorded. Repeat the measurement 6 times, and calculate the ion meter potential measurement repeatability according to formula (13): Z(E-E)
Where: E-high resistance state, primary and secondary measurement indication, mVE-the arithmetic mean of 6 measurement indications: mV. 5.3.6.2 pX measurement repeatability
Adjust the ion meter according to 5.3.3.2, insert a high resistance in series into the input circuit, input a potential value equivalent to 6 pX units into the ion meter, record the ion meter indication, repeat the measurement 6 times, and calculate the pX measurement repeatability according to formula (14): Spx
Z(pXx -pxx)2
Where: pXx—high resistance state, the,th measurement indication, pX; pX, the arithmetic mean of the 6 measurement indications, pX. 5.3.7 Temperature compensator error
5.3.7.1 Instruments with manual temperature compensation
The ion meter is set to X, measurement function, and the temperature compensator is adjusted between its upper and lower limits. The change in the ion meter indication should be consistent with its scale division (or minimum display) value. Then adjust the temperature compensator to a temperature other than 25 for calibration. The calibration points should be selected from at least 4 nominal temperature points including the upper and lower limit points of the temperature compensator. At each temperature calibration point, increase and decrease the input potential by the method of each input equivalent to the potential of 6X value at the temperature, and find the average value of the indication when increasing and decreasing the input. Calculate the error of the temperature compensator according to formula (15): Apx,-6
where: px is the average value of the indication.1 Potential measurement repeatability
The ion meter is set to the potential measurement function. High resistance is input into the circuit, 300mV potential is input into the ion meter, and the ion meter indication is recorded. Repeat the measurement 6 times, and calculate the ion meter potential measurement repeatability according to formula (13): Z(E-E)
Where: E-high resistance state, primary and secondary measurement indication, mVE-the arithmetic mean of 6 measurement indications: mV. 5.3.6.2 pX measurement repeatability
Adjust the ion meter according to 5.3.3.2, insert a high resistance in series into the input circuit, input a potential value equivalent to 6 pX units into the ion meter, record the ion meter indication, repeat the measurement 6 times, and calculate the pX measurement repeatability according to formula (14): Spx
Z(pXx -pxx)2
Where: pXx—high resistance state, the,th measurement indication, pX; pX, the arithmetic mean of the 6 measurement indications, pX. 5.3.7 Temperature compensator error
5.3.7.1 Instruments with manual temperature compensation
The ion meter is set to X, measurement function, and the temperature compensator is adjusted between its upper and lower limits. The change in the ion meter indication should be consistent with its scale division (or minimum display) value. Then adjust the temperature compensator to a temperature other than 25 for calibration. The calibration points should be selected from at least 4 nominal temperature points including the upper and lower limit points of the temperature compensator. At each temperature calibration point, increase and decrease the input potential by the method of each input equivalent to the potential of 6X value at the temperature, and find the average value of the indication when increasing and decreasing the input. Calculate the error of the temperature compensator according to formula (15): Apx,-6
where: px is the average value of the indication.
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