Some standard content:
National Metrology Verification Regulations of the People's Republic of China JJG982—2003
DC Resistance Box
DC Resistance Box
Issued on September 23, 2003
Implementation on March 23, 2004
Issued by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China JJG982—2003
Verification Regulation of
DC Resistance Box
JJG982—2003
Replaces JJG166—1993
(DC Resistance Box Part)
This verification regulation was approved by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China on September 23, 2003, and came into effect on March 23, 2004.
Responsible unit:
Main drafting unit:
Participating drafting unit:
National Electromagnetic Metrology Technical Committee
Henan Institute of Metrology and Testing
Zhengzhou Water Conservancy School, Henan Province
514 Institute of the Fifth Academy of China Aerospace Science and Technology Corporation This regulation entrusts the National Electromagnetic Metrology Technical Committee to be responsible for interpreting this regulation Main drafters:
Participating drafters:
Yang Mingjing
Liu Wenfang
Li Xingfu
Li Jidong
JJG982—2 003
(Henan Institute of Metrology and Testing)
(Henan Institute of Metrology and Testing)
(Henan Institute of Metrology and Testing)
(Henan Institute of Metrology and Testing)
(Zhengzhou Water Conservancy School)
(514th Institute of the 5th Academy of China Aerospace Science and Technology Corporation) 1
References
Terms and Terms·
5 Metrology Performance Requirements
5.1 Indication Error
Stability
Accuracy Grade
Error of Residual Resistance||tt| |5.5 Resistance box switch variation
6 General technical requirements
6.1 Appearance and marking
Insulation resistance
Power frequency withstand voltage test
6.4 Requirements for the influence quantity of DC resistance box
7 Measuring instrument control-
Verification conditions
Verification items
7.3 Verification method
7.4 Processing of verification results
Verification cycle.
JJG982—2003
Appendix A Working principle of digital voltmeter verification resistance box Appendix B Original record of DC resistance box calibration
Appendix C Format of the inner page of the DC resistance box calibration certificate Appendix D Format of the inner page of the calibration result notice
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1 Scope
JJG982—2003
Verification procedure for DC resistance box
This procedure is applicable to the initial calibration, subsequent calibration and in-use inspection of DC resistance boxes with accuracy levels ranging from 0.002 to 10, resistance values ranging from 10-3Q to 10°Q, and line insulation voltage not exceeding 650V. This procedure is not applicable to the calibration of resistance boxes and AC resistance boxes that are internal components of instruments or developed for special requirements.
2 References
JF1059--1999 "Evaluation and Expression of Uncertainty in Measurement" CB4793.1-1995 "Safety Requirements for Electrical Equipment for Measurement, Control and Laboratory Use" JB/T8225-1999 "Laboratory DC Resistors" GB/T13978-1992 "General Technical Conditions for Digital Multimeters" When using this procedure, attention should be paid to using the current valid versions of the above references. 3 Terms and Terminology
3.1 Decade Resistors
Multi-value resistors that use switching devices to select resistance value combinations in equal ascending steps, each step corresponding to the increment of the decade resistance value (for example, 0.1Q, 12 or 102). Note: Decade resistors generally allow the selection of 10, 11 or 12 resistance values (including zero). The decade resistors in the DC resistance box are also called decade resistance disks or decade disks.
3.2 Residual resistance
For a DC resistance box with zero position, when all the switch devices are in the zero position, the resistance value at the output of the resistance box.
For a DC resistance box with no zero position, when all the switch devices are in the minimum position, the resistance value at the output of the resistance box.
3.3 Variation
When a certain influencing quantity takes two specified values successively, while other influencing quantities are kept under their reference conditions, the difference between two actual values measured.
3.4 Influencing quantity
The quantity that tends to cause an undesirable change in the resistance value of the resistance box. 3.5 Reference conditions
Some specified conditions that enable the resistance box to meet the relevant indication error requirements. For each influencing quantity, these reference conditions can be a fixed single value or a range of values. 4 Overview
A DC resistance box is a multi-value resistor composed of a single or several decade resistors connected in series. Under reference conditions, 1
JJG982-2003
Each decade disk of the DC resistance box has its own corresponding accuracy grade 5 Metrology performance requirements
5.1 Indication error
5.1.1 Absolute error of indication
The absolute error of indication of the DC resistance box is expressed in the form of: A=RR
Where: 4-absolute error of indication, Q;-nominal value of the indication of the resistance box being checked, 2; R.
-actual value of the indication of the resistance box being checked, Q. 5.1.2 Relative error of indication
The relative error of indication of the DC resistance box is expressed in the form of: AR.-Rx,
×100%
Where:-relative error of indication.
5.2 Stability
The stability of the resistance box indication is expressed as annual stability: Rx-Rx
Where: one-year stability error;
the calibration value of the indication of the resistance box in the previous year. Only decade resistance disks above level 0.01 (including 0.01) are evaluated for annual stability. 5.3 Accuracy level
The accuracy level of each decade resistance disk in the DC resistance box is divided into twelve levels from level 0.002 to level 10. The maximum allowable error of the indication of each level of decade resistance disk and the annual stability error limit shall meet the requirements of Table 1. Table 1 Maximum allowable error of each grade of decade resistance disk and annual stability error limit Grade index/(%)
Annual stability error limit/(%)
Maximum allowable error/(%)
It is customary to call the highest grade of decade disk in a resistance box the grade of the resistance box. For example, the highest grade of decade disk in ZX54 DC resistance box is 0.01 grade, and ZX54 is often referred to as 0.01 grade resistance box. This is just a customary name. 2
Grade index/(%)
5.4 Error of residual resistance
JJG982—2003
Table 1 (continued)
Annual stability error limit/(%)
Maximum allowable error/(%)
5.4.1 For DC resistance boxes with zero-position gears on decade resistance disks, the residual resistance value shall not exceed 50% of the maximum allowable absolute error of its minimum step resistance value, otherwise the manufacturer must indicate the nominal value of the residual resistance and its tolerance, which shall not be greater than 5 times the maximum allowable absolute error of the minimum step resistance value, and the maximum allowable error shall not exceed 10mQ. 5.4.2 For DC resistance boxes with no zero-position gears on decade resistance disks, the residual resistance value is the minimum step value of the zero-position gearless decade resistance disk, and its tolerance is the allowable absolute error of the minimum step resistance value of the disk. 5.5 Resistance box switch variation
The resistance variation caused by each switch contact of the resistance box should not be greater than 50% of the allowable absolute error value of the minimum step resistance value. When the minimum step resistance value is less than or equal to 0.01Q and the highest accuracy level of the resistance box is less than or equal to level 0.1, the variation of the switch contact resistance should not be greater than the allowable absolute error value of the minimum step resistance value. 6 General technical requirements
6.1 Appearance and marking
The nameplate or shell of the resistance box should have the following main markings: product name, model, number, manufacturer name (or factory mark), nominal (or maximum) power (current or voltage), nominal value of decade resistance and corresponding accuracy level. Domestic DC resistance boxes should have M mark and number. 6.2 Insulation resistance
Insulation resistance is the resistance between the circuit of the resistance box and any other external metal parts that are not electrically connected to the circuit. 6.2.1 For a resistance box containing decade resistors ranging from 0.05 to 10, the insulation resistance shall not be less than 100MQ.
6.2.2 For resistance boxes with decade resistors of 0.01, 0.02 and above and resistance values less than or equal to 10°Q, the insulation resistance shall not be less than 500MQ.
6.2.3 For other resistance boxes, the insulation resistance shall be one million times the nominal value of the maximum resistance of the resistance box, but shall not be less than 500MQ.
6.3 Power frequency withstand voltage test
The circuit of the resistance box and the reference ground terminal for testing shall be able to withstand a test of an actual sinusoidal AC voltage of 2kV with a frequency of (45~65) Hz for 1 minute without breakdown or arcing. The reference ground terminal in the power frequency withstand voltage test shall include all exposed conductive parts that are not electrically connected to the circuit; if there are no conductive parts on the insulating shell of the resistance box, the reference ground terminal shall be the metal foil wrapped around the resistance box to be tested (there should be a 20mm gap between the metal box and the circuit). 6.4 Requirements for the influence quantity of DC resistance box
JJG982—2003
The nominal use range of the influence quantity of DC resistance box is shown in Table 2. Table 2 Nominal use range
Influence quantity
Environmental temperature (atmosphere, temperature control tank)
Relative humidity
Power (voltage)
Grade index/(%)
0.005~0.02
All grades
All grades
Nominal use range
20℃±2℃
20℃±5℃
20℃±10℃
25%~75%
Manufacturer specifiesWww.bzxZ.net
When the DC resistance box is under the conditions given in Table 2, when a single influence quantity changes to any value within the nominal use range, the variation of the resistance value shall not exceed the corresponding grade index value. Measuring instrument control
Measuring instrument control includes: initial verification, subsequent verification and in-use inspection. 7.1 Verification conditions
7.1.1 Environmental conditions for verification
The environmental conditions to be observed when determining the indication error are as described in Table 3. Table 3 Environmental conditions for verification
Influence quantity
Environmental temperature
(atmosphere, temperature control bath)
Relative humidity
Grade index/(%)
0.005~0.01
All grades
Note: There should be no tolerance for the reference range.
Reference conditions
The DC resistance box must be calibrated after it has been stable for 24 hours under the reference conditions for verification. 7.1.2 Calibration device
Reference range during calibration
20℃±0.2℃
20℃±0.5℃
20℃±1℃
20℃±2℃
20℃±3℃
40%~70%
7.1.2.1 The grade index of the standard device used as the standard for calibrating the resistance box shall at least conform to the provisions of Table 4. 7.1.2.2 When calibrating the resistance box, the expanded uncertainty (k=3) caused by factors such as the standard instrument, calibration device and environmental conditions should not be greater than 1/3 of the grade index of the inspected object. 4
JJG982—2003
Table 4 Correspondence table of the relationship between the grade index of the standard and the inspected object Decimal dial grade index of the inspected resistance box/(%) 0.002
Grade index of the standard instrument/(%)
7.1.2.3 The standard deviation of repeated measurements of the calibration device should not be greater than 1/10 of the grade index of the inspected object, and the number of measurements should be greater than or equal to 10 times.
7.1.2.4 The uncertainty introduced by connection resistance, parasitic potential, insulation leakage, electrostatic induction, electromagnetic interference and other factors during verification is generally not greater than 1/20 of the grade index to be verified. 7.1.2.5 The uncertainty introduced by the sensitivity in the verification device shall not be greater than 1/10 of the grade index to be verified. 7.1.3 Use a 500V insulation resistance meter or high resistance meter of not less than grade 10 to measure the insulation resistance of the DC resistance box. Use a power frequency withstand voltage tester with a basic error of not more than 5% to conduct the power frequency withstand voltage test of the resistance box. 7.1.4
7.2 Verification items
See Table 5 for the verification items of the DC resistance box.
Table 5 Verification Items
Verification Category
Verification Items
Appearance and Circuit Inspection
Insulation Resistance
Power Frequency Withstand Voltage Test
Residual Resistance
Switch Variation
Indication Error
First Verification
Note: "+" indicates verification, "_" indicates no verification Subsequent Verification
In-use Inspection
7.3 Verification Method
7.3.1 Appearance and Circuit Inspection
JJG982-2003
7.3.1.1 Visually inspect the appearance, nameplate, etc. of the resistor box, which shall comply with the provisions of 6.1. 7.3.1.2 Use an ohmmeter or multimeter to make a preliminary measurement of the resistance of each decade disk of the resistor box to check whether its resistance is open or short-circuited.
7.3.2 Insulation resistance test
According to the requirements of 7.1.3, select an insulation resistance meter or a high resistance meter, and measure the insulation resistance of the resistance box to be tested according to the test position specified in 6.2. The reading on the insulation resistance meter or high resistance meter should be read 1 minute after the voltage is applied, and its value shall comply with the provisions of 6.2.
7.3.3 Power frequency withstand voltage test
According to the requirements of 7.1.4, select a withstand voltage tester, and perform a power frequency withstand voltage test according to the provisions of 6.3. There should be no breakdown or arcing.
7.3.4 Verification of residual resistance
The residual resistance of the DC resistance box shall be verified by a milliohmmeter or a double bridge with a resolution of no more than 0.1mQ, which is two levels higher than the accuracy level of the undisk, or other measuring instruments that can meet the requirements. Before measurement, each decade resistance disk should be rotated back and forth within the maximum range for no less than three times, and then the indication should be placed at zero or the last position of each disk.
The measurement should be repeated three times, and the average of the three measurement results is taken as the measurement result. 7.3.5 Verification of switch variation
Use a low resistance meter or double bridge with a resolution of no more than 0.1mQ2 or other measuring instruments that meet the requirements to measure according to the following steps:
7.3.5.1 Before measurement, rotate each decade resistance disk several times (no less than three times) within the maximum range, set the end switch value to 1, or for a resistance box without a zero position, set the zero-position decade resistance disk value to the last position, and set the other decade disk values to zero, and measure and record the resistance value M at this time. 。 7.3.5.2 After rotating the first decade disk back and forth, reset the indication to zero, and keep the other decade disks stationary. Measure and record the resistance value M at this time; then the first decade disk switch resistance variation is: A,=Mo-M
7.3.5.3 Measure each decade disk in turn in a similar way to 7.3.5.2 to obtain M, then the switch resistance variation of the tenth decade resistance disk is:
4, = M.-1 - M
Take the largest switch resistance variation value of the above multiple decade disks as the switch resistance variation value of the resistance box, which should meet the requirements of 5.5.
7.3.6 Verification of indication error
The verification of indication error is carried out under reference conditions. According to the grade index and nominal value of the object to be verified, multiple verification methods such as direct measurement method, substitution method with nominal value and digital table method can be used. Considering the consistency between the verification state and the use state, the overall verification method is generally used as much as possible when verifying the resistance box. 7.3.6.1 Direct measurement method
JJG982-2003
When the resistance measuring instrument or device with two accuracy levels higher than the tested resistance is used to measure the tested resistance value, the direct measurement method can be used. The verification result of the resistance value of the tested resistance R, is: Rx=Ax
Where: A—the indication of the resistance measuring instrument.
Common resistance measuring instruments or devices include bridges, current comparators, voltage comparators, etc. 7.3.6.2 Same nominal value substitution method
When the resistance measuring instrument or device cannot reach an accuracy level higher than the tested resistance R, by two levels, and there is a standard resistance box R, with the same nominal value as the tested resistance R and two accuracy levels higher than the tested resistance, the same nominal value transfer method can be used to calibrate the resistance value of the tested resistance box. The most commonly used same nominal value transfer method is the substitution method. The substitution method is to use a resistance measuring (or comparison) instrument to measure the resistance values of the standard resistance box R and the resistance box R to be tested in turn. The verification result is Rx=Rs+ (Ax-As)
where: A is the indication of the measuring instrument when measuring R; Ax is the indication of the measuring instrument when measuring Rx. Note: The uncertainty introduced by the resistance measuring instrument used for comparison should not be greater than 1/10 of the grade index of the tested object. 7.3.6.3 Digital meter method
1) Direct measurement method of digital meter
Under the verification conditions, when the expanded uncertainty (h=3) brought by the ohmmeter of the digital ohmmeter or digital multimeter when measuring resistance is less than 1/3 of the grade index to be tested, the resistance value of the resistance box Rx to be tested can be directly measured with the ohmmeter or the ohmmeter of the digital multimeter, and the verification result is: Rx=Bx
Where: B, — ohmmeter display reading.
2) Digital voltmeter method
Under the verification conditions, the resistance value of the resistance box to be tested is determined by measuring the voltage on the standard resistor and the resistance box to be tested using a standard resistor, a constant current source and a digital voltmeter. When the expanded uncertainty (h=3) introduced by the measuring device is less than 1/3 of the grade index to be tested, the value of the resistance box to be tested can be measured. For the measurement principle and method, see Appendix A.
7.3.6.4 Other certified methods that ensure that they meet the requirements of 7.1.2.2 regarding the expanded uncertainty of verification are permitted.
7.4 Processing of verification results
7.4.1 The verification data shall be rounded off to 1/10 of the maximum allowable error of each decimal disk according to the rounding-off and even number rules required by the digital rounding specification, that is, the last digit of the verification data of the first point of each decimal disk shall be rounded off to the digit corresponding to 1/10 of the maximum allowable error of that point, and the digits of the remaining points shall be aligned with the first point. Note: 1. For the resistance box with a zero position for the switching device, each disk shall not contain residual resistance. 2. For the resistance box without a zero position for the switching device, the decimal disk without a zero position contains residual resistance, and the remaining disks shall not contain residual resistance.
7.4.2 The residual resistance data is rounded to 0.1m2. 7.4.3 The insulation resistance, power frequency withstand voltage test and switch resistance variation do not need to give the verification data, only judge whether it is qualified or not. 7
7.4.4 Grading
JJG982—2003
The verification is carried out according to the items of this regulation and the following principles are followed. 7.4.4.1 For the resistance box containing 0.01 grade or above resistance disk, if all the verification items are qualified, there is a verification certificate from the previous year and the annual stability of the corresponding grade is qualified, it can be graded and issued a verification certificate. If there is no verification certificate from the previous year or it is the first time to be verified, a verification certificate will be issued but no classification will be given and it will be noted that "No annual stability assessment, no classification for the time being". 7.4.4.2 For the other resistance boxes, if all the verification items are qualified, it can be graded and issued a verification certificate. 7.4.4.3 Each decade disk of the resistance box is graded to the corresponding grade. 7.4.4.4 For those who fail to meet the original grade, it is allowed to be used at a lower grade, but it must meet all the technical requirements of the specified grade. 7.4.5 Verification certificate or verification result notice. 7.4.5.1 A verification certificate shall be issued for those who meet all the mandatory inspection items listed in Table 5: For those who fail to meet one item, a verification result notice shall be issued, and the reason for failure shall be noted on the verification result notice. 7.4.5.2 The certificate shall give the verification data, measurement uncertainty, temperature and relative humidity during verification and conclusion. For resistance boxes whose decade resistance disks are all at level 0.1 or below, generally only conclusions can be given without data. 7.4.6 The verification of repaired resistance boxes shall be handled as the first verification. 7.5 Verification cycle
The verification cycle of resistance boxes generally does not exceed 1 year.
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