Some standard content:
National Metrology Verification Regulation of the People's Republic of China JJG 376—2007
Electrolytic Conductivity Meters2007 - 11 21 Issued
Implementation on 2008-05-21
The General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China issued JJG376-2007
Verification Regulation of
Electrolytic Conductivity Meters-KAONiKAca
JJG 3762007
Replaces JJG 376—-1985
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 took effect on May 21, 2008.
Responsible unit: National Physical and Chemical Metrology Technical Committee Drafting unit: China Institute of Metrology This regulation is entrusted to the National Physical and Chemical Metrology Technical Committee to be responsible for the interpretation of this regulation. Main drafters:
JJG376—2007
Zhu Xiaoping (China Institute of Metrology) Participating drafters:
Que Ying (China Institute of Metrology)
Wang Hai (China Institute of Metrology)
Scope·
References
Terms and measurement units
Metrological performance requirements
Electronic unit repeatability
Electrical unit reference error
Conductivity cell Constant indication error
Temperature coefficient indication error
Temperature measurement indication error·
Instrument reference error
Instrument repeatability
General technical requirements
Control of measuring instruments
Verification conditions…
Verification items
Verification methods
Processing of verification results
Verification cycle·
JJG376—2007
Concentration of conductivity standard solution and its conductivity valueAppendix A
Example of conductivity meter verification record
Appendix B
Appendix C Example of the format of the inner page of the verification certificate
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（1）
（2）
（2）
（2）
(5）)
1Scope
JJG376-—2007
Conductivity meter calibration procedure
This procedure is applicable to the initial calibration, subsequent calibration and in-use inspection of electrolyte conductivity meters. The calibration of resistivity meters, salinity meters based on the conductivity measurement principle and total dissolved solids (TDS) meters can be implemented as a reference. OHENT
2References
OIMLR68EditionAgaCatibrationmethod ideonductivitycellBSEN60746
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Part3:Electrolytio
3 Terms and units of measurement
bath liquid) conductivityelectrolytie
(electrolyte
electrochemicalanalyzers
The ratio of current and potential difference when ionic charges in electrolyte solution move in conductivity cell
In the formula: G
ground conductivity, S:||tt| |Current through an electrolyte solution
The potential difference between the electrodes, V
Resistance is the reciprocal of
3.2 (electrolysis)
, and the unit is Q.
Conductivity
alectrolyticconductivity
The conductivity of an electrolyte solution is defined by the following formula: Where: K
Conductivity
Current density
EElectric field intensity,
Resistivity is the reciprocal of conductivity,
3.3Conductivity cell constant
cell The conductivity cell constant is calculated by formula (3): where: Kel
conductivity cell constant, m-
METROLOG
effective distance between measuring electrodes, m; A-effective cross-sectional area of the liquid column between electrodes, m. G
Because the effective geometric parameters of the conductivity cell are difficult to measure directly, the conductivity cell constant is generally determined by measuring the conductivity of a standard material with an accurately known conductivity and using a relative measurement method. The conductivity cell constant, conductivity and conductivity have the following relationship: K KG
Note: Usually the conductivity cell constant has a constant value within a certain range. Beyond this range, the electrode polarization effect and other effects may cause the electrode constant to change.
3.4 Temperature coefficient temperature coefficicnt The relative change in the conductivity of the electrolyte solution for every 1°C change in temperature. For strong electrolytes with a conductivity greater than 1×10-4S·m-, the temperature coefficient α can be approximately expressed by formula (5): α xr(tir)
X 100%
Where: kk—conductivity at temperature t; kk—conductivity at reference temperature (r).
4 Overview
Conductivity meters are used to measure the conductivity of electrolyte solutions. The measurement principle of conductivity meters is based on the relationship between conductivity and conductivity and conductivity cell constant [Formula (4): A stable AC signal is applied between the electrodes of the conductivity cell, the conductivity of the solution between the electrodes is measured, and the conductivity is obtained based on the input conductivity cell constant. The conductivity meter is mainly composed of two parts: an electronic unit and a sensor unit. The electronic unit usually includes a signal generator, a measuring unit (AC bridge or proportional amplifier), a detector, a reading part, etc. In addition, there is a unit for realizing the conductivity cell constant adjustment, temperature compensation and temperature measurement functions. The sensor unit mainly includes a conductivity cell, and usually also has a temperature sensor to realize the transmission of electrical signals between the solution and the electronic unit and measure the solution temperature. The calibration of the conductivity meter includes two parts: the electronic unit calibration and the instrument calibration. In this regulation, the conductivity meter is divided into 8 levels: 0.2, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 and 4.0 according to the verification results of the small error of the electronic unit: the metrological performance requirements of each level of instruments are shown in Table 1. 5 Metrological performance requirements
5.1 Electronic unit repeatability
The verification results shall comply with the provisions of Table 1.
5.2 Electronic unit reference error
. The verification results shall comply with the provisions of Table 1.
5.3 Conductivity cell constant indication error
The verification results shall comply with the provisions of Table 1.
5.4 Temperature coefficient indication error
The verification results shall comply with the provisions of Table 1.
5.5 Temperature measurement indication error
The verification results shall comply with the provisions of Table 1.
5.6 Instrument reference error
The verification results shall comply with the provisions of Table 1.
5.7 Instrument repeatability
JJG 376—2007
08°0+
500'0+
（2%)
Matching verification
Electronic unit verification
Verification results shall comply with the provisions of Table 1
6 General technical requirements
JJG376-2007
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The instrument surface should be smooth and flat. The instrument function keys should work normally, and the fasteners should not be loose. The markings on the instrument panel should be clear and complete. The display of the digital display instrument should be clear and complete, and the pointer of the pointer instrument should not be blocked. The instrument nameplate should indicate its manufacturer name, instrument name, model, specification, factory number and factory date. The nameplate should be clear
The sensor unit should be free of cracks, damage, contaminants, and the platinum black on the platinum black electrode should not be obviously peeled off. 7. Measuring instrument control
Measuring instrument control includes direct verification
7.1 Verification conditions
7.1.1 Environmental conditions
Continuous inspection
Testing and in-use inspection
The environmental conditions for verification shall comply with the provisions of Table 2
Environmental conditions for verification
Instrument level
20 years2
Relative humidity %RH
Standard solution temperature fluctuation
Action range
Electromagnetic field vibration
Except for the ground, there shall be no obvious electric disturbance and no significant vibration source
7.1.2 Solution conductivity simulation device
It is a standard device for verifying the metrological performance of the electronic unit. The resistance value setting shall meet the requirements of the "verification method". The uncertainty of the AC resistance value shall be better than 1/3 of the measurement uncertainty of the electronic unit of the instrument under test, and shall be compatible with the use frequency of common conductivity meters. The solution conductivity simulation device with a relative error of resistance value not exceeding 0.07% can meet the calibration requirements of conductivity meters of all levels. 7.1.3 Conductivity standard solution
The relative uncertainty of the reference value of the standard solution used in the calibration should be less than or equal to 0.25 (k-2). Potassium chloride conductivity solution standard material can be used, or potassium chloride conductivity solid standard material can be selected and prepared according to the provisions of the appendix. 7.1.4 Constant temperature device
The constant temperature device is used to calibrate the temperature measurement indication error of the instrument and control the temperature of the standard solution. Its temperature fluctuation should4
comply with the provisions of Table 2.
7.1.5 Standard thermometer
JJG376-2007
The standard thermometer is used to calibrate the temperature measurement indication error of the instrument and monitor the temperature fluctuation of the constant temperature device. The thermometer with an indication error within ±0.05℃ can meet the calibration requirements of conductivity meters of all levels. 7.1.6 Resistance box
The analog temperature sensor is connected to the electronic unit and is used to adjust the temperature display value of the electronic unit. 7.2 Verification items
The verification items for the initial verification, subsequent verification and in-use inspection of the conductivity meter are shown in Table 3. SOM: Self-examination of the performance
Verification items
Appearance inspection
Electronic unit reference error
Conductivity cell constant indication error
Temperature coefficient indication
Electronic unit weight
Temperature indication
Instrument reference
Instrument weight
Note: "+
Sound verification
Please check the inspection items,
7.3 Verification method
7.3.1 Appearance inspection
Inspect in accordance with Article 6
7.3.2 Electronic unit repeatability
Electronic unit verification wiring diagram is shown in the figure
Conductivity The conductivity meter
is an item that can be checked.
as shown.
Jingchejiao
Figure 1 Schematic diagram of electronic unit calibration wiring
Inspection during use
Figure 1 (a) is a schematic diagram of the calibration wiring of the electronic unit of the conductivity meter equipped with a 2-electrode conductivity cell. 1 and 2 are connected to the two output ends of the standard conductivity: T1 and T2 are respectively connected to the resistance of the analog temperature probe (only applicable to instruments that require temperature input). Figure 1 (b) is a schematic diagram of the calibration wiring of the electronic unit of the conductivity meter equipped with a 4-electrode conductivity cell. 1 and 4 connection lines correspond to the two current electrodes of the conductivity cell, and 2 and 3 connection lines correspond to the two voltage electrodes of the conductivity cell 5
JJG 376—2007
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1) Connect the wires as shown in Figure 1. Set the temperature coefficient of the conductivity meter to 0.00% or "no compensation"; or adjust the temperature indication to the instrument reference overflow TR (usually 25.0℃). Note: If the conductivity meter does not have a temperature compensation function: these function keys can be omitted and the calibration can be performed directly. 2) For conductivity meters with a conductivity cell constant display function, adjust the conductivity cell constant to the reference value KelR (usually 1.000cm1); for conductivity meters without a conductivity cell constant display function, select a standard conductivity G° that is equal to or close to the upper limit of the range being tested as the input, adjust the instrument reading to G, and the conductivity cell constant is considered to be 1:000cm-.
3) Connect any standard conductivity G on the mid-range (such as 100 μS) and calculate the corresponding standard conductivity: K.=K.all G. Read the conductivity meter measurement value rM4) Repeat the above operation 6 times, calculate the arithmetic mean M of the 6 measurement values, which should meet the requirements of Table 1. The ratio of the standard deviation of a single measurement result to the upper limit of the corresponding range (Formula 6) is used to evaluate the electronic unit refolding. (-- m)
×100%
Where: KM: the indication of the ith measurement:
rr——the upper limit of the conductivity meter's range. 7.3.3 Electronic unit reference error
1) Connect as shown in Figure 1. Set the conductivity meter temperature coefficient to 0.00% or "no compensation"; or adjust the temperature indication to the instrument reference temperature Tk (usually 25.0℃). Note: If the conductivity meter does not have temperature compensation kinetic energy, these function keys can be omitted and the calibration can be carried out directly. 2) For conductivity meters with conductivity cell constant display function, adjust the conductivity cell constant to the reference value Kcellk (usually 1.000cm-1). For conductivity meters without conductivity cell constant display function, select the standard conductivity G equal to or close to the upper limit of the range to be tested as the input quantity, adjust the instrument reading to G, and then the conductivity cell constant is considered to be 1.000 cm-1.
3) Connect the standard conductivity G, calculate the corresponding standard conductivity: r=K.lleG, and read the corresponding instrument measurement value RM. Calculate the electronic unit reference error according to formula (7). Ar xm ≤ × 100%
Usually, at least 3 points are calibrated for each range, and these calibration points should be dispersed within the range. 7.3.4 Conductivity cell constant indication error
1) Connect as shown in Figure 1. The conductivity meter temperature coefficient is set to 0.00% or "no compensation", or the temperature indication is adjusted to the instrument reference temperature Tk (usually 25.0℃). Note: If the conductivity meter does not have temperature compensation function, these function keys can be omitted and the calibration can be performed directly. 2) Connect any standard conductivity G on the mid-range (such as 100μS). Set the constant adjuster to Kk and read the conductivity meter measurement value KMR
3) Adjust the conductivity cell constant from Kell R to Kellv=0.8×Kell R, read the conductivity meter measurement value kmv and calculate the indication error when the conductivity cell constant is set to Kellv according to formula (8). AKel - Kkell R · KMV - Kel vKMR
JJG376—2007
4) Adjust the conductivity cell constant to Kcllv-1.2×KcellR, and calculate the conductivity cell constant indication error according to step 3). For conductivity meters without constant adjustment function or constants that cannot be displayed, this item is exempted from inspection. 7.3.5 Overflow coefficient indication error
1) Connect any standard conductivity G in the range as shown in Figure 1. (For example, 100μS). Set the constant adjuster to Kcelk (usually 1.00cm); set the temperature compensation coefficient to 0.00% or "no compensation", or adjust the temperature indication to the reference temperature TR specified by the instrument (usually 25.0C), and read the instrument measurement value kMR. 2) Set the temperature coefficient α=2.00%.℃1. Adjust the temperature sensor analog resistance so that the temperature indication is T=15℃, and read the conductivity meter measurement value MV. Calculate the indication error of the temperature coefficient according to formula (9). Aα - --MRKMV
×100—α
KMV(T-TR)
3) Adjust the temperature sensor analog resistance so that the temperature indication is T-35℃, and calculate the indication error of the temperature coefficient according to step 2).
4) Set the temperature coefficient α=1.50%,℃-1. Repeat steps 2) and 3). 5) Set the temperature coefficient α2.50%·℃-1. Repeat steps 2) and 3). For conductivity meters without temperature compensation function, this test is exempted. Note: 4) and 5) are only necessary operations for the first calibration of the instrument. 7.3.6 Temperature indication error
1) After connecting the temperature sensor of the conductivity meter to the electronic unit, place it in the same constant temperature bath with the standard thermometer, and keep the standard thermometer and temperature sensor as close as possible. 2) Control the temperature of the thermostatic bath to the instrument reference temperature TR (usually 25°C), read the standard thermometer measurement value T. and the conductivity meter temperature measurement value TM at the same time, and calculate the temperature indication error of a single measurement according to formula (10). AT = TM-I.
3) Repeat step 2) for 3 times, and calculate the arithmetic mean of the temperature indication errors for 3 times as the indication error of the instrument temperature measurement.
4) Control the temperature of the thermostat bath to T, = 15℃ and T = 35℃ respectively, repeat the above steps, and calculate the indication error of the corresponding temperature.
Conductivity meters without temperature measurement function are exempt from this test. Note: 4) is only required for the first calibration of the instrument. 7.3.7 Instrument reference error
7.3.7.1 Calibration of conductivity cell constant
1) Connect the electronic unit to the sensor unit. Adjust the conductivity cell constant to KlR (usually 1.000cm1) and set the temperature coefficient to 0.00% or "no compensation". 2) Select standard solution 1 and standard solution 2 in the two ranges respectively, and place them in a thermostat bath with a temperature of T (usually 25.0℃).
3) Wash the sensor unit thoroughly and place it in standard solution 1. After reaching equilibrium, read the conductivity meter measurement value KMI, and calculate the conductivity cell constant Kell according to formula (11): Kli = KellR × n
JJG376-2007
Where: --- the conductivity value of standard solution 1 at reference temperature T. TIKAONIKAca
4) After fully washing the sensor unit of the instrument under test, put it into the standard solution 2. After equilibrium, the conductivity meter measurement value is cM2: According to formula (12), calculate the conductivity cell constant Kell2Kella = KellrX Ke
Where: K2-the conductivity value of standard solution 2 at reference temperature TR. (12)
5) Repeat steps 3) and 4), measure three times, and calculate the arithmetic mean values of the conductivity cell constants Ki and Kll2 obtained from the three measurements respectively
6) Calculate the average values of Kl and Kll2 as the conductivity cell constant 180
Ke+Kll2
The conductivity cell calibration has clear requirements
Note: If the instrument manual has specific requirements for conductivitywwW.bzxz.Net
, it can also be calibrated according to the instrument manual. 7.3.7.2 Instrument reference error calibration
7) Adjust the conductivity cell constant to K, and keep other settings unchanged (13)
The instrument measurement value is KMI.
Measure the standard solution
Repeat the operation and measure three times to obtain the average value MAK
Calculate the reference error when measuring the standard solution according to formula (14): DO
8) Change the instrument settings, measure standard solution 2, obtain the average value of the instrument's measurement of standard solution 2, and calculate the reference error when measuring standard solution 2 according to formula (15). A
7.3.8 Repeat the instrument measurement
K×100
Repeat the measurement of standard solution 1 or standard solution 2 for a total of 6 times: Calculate the ratio of the single measurement standard deviation to the full scale according to formula (6), which represents the repeatability of the instrument measurement result. 7.4 Processing of verification results
An instrument that meets the requirements of this regulation after verification is a qualified instrument and is issued a verification certificate. The verification certificate should give various verification results and instrument levels. An instrument that is determined to be a certain level must meet all metrological performance requirements of the instrument at that level. If the individual range of the instrument does not meet the requirements of the level, the limited range should be indicated. For the instrument that does not meet the requirements, a verification result notice shall be issued, and the unqualified items shall be noted. When the verification result of the electronic unit meets the requirements of this regulation, but the matching verification of the original sensor unit required for the instrument exceeds the requirements of this regulation, the sensor unit can be replaced and the matching verification can be re-performed. The qualified instrument is a qualified instrument and a verification certificate shall be issued.
7.5 Verification cycle
The verification cycle shall generally not exceed 1 year.
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