JJG 131-2004 Verification Procedure for Electric Contact Glass Mercury Thermometers JJG131-2004 Standard download decompression password: www.bzxz.net
This procedure is applicable to the initial verification, subsequent verification and in-use inspection of electric contact glass mercury thermometers with various ranges of measurement range from -30℃ to 300℃. Fixed contact thermometers without scales can be calibrated or tested in accordance with this procedure.

National Metrology Verification Regulation of the People's Republic of China JJG131-2004
Electric Contact Mercury-in-Glass Thermometers
Electric Contact Mercury-in-Glass Thermometers2004-03-02Promulgated
Implementation on 2004-09-02
Promulgated by the General Administration of Quality Supervision, Inspection and QuarantineJJG131—2004
Electric Contact Mercury-in-Glass Thermometers
Verification Regulation of theElectric Contact Mercury-in-Glass ThermometersJJG131—2004
Replaces JJG131-1991
This regulation was approved by the General Administration of Quality Supervision, Inspection and Quarantine on March 2, 2004, and came into effect on September 2, 2004.
Responsible unit:
Drafting unit:
National Technical Committee for Temperature Metrology
Beijing Institute of Metrology
This regulation entrusts the National Technical Committee for Temperature Metrology to be responsible for interpreting this regulation. Main drafters of this regulation:
Participating drafters:
JJG131—2004
(Beijing Institute of Metrology)
(Beijing Institute of Metrology)
(Beijing Institute of Metrology)| |tt||(Beijing Institute of Metrology)
(Beijing Institute of Metrology)
References·
3 Terms
4.1 Principle
4.2 Construction·
5 Metrology performance requirements,
5.1 Indication stability·
5.2 Indication error
5.3 Action error
5.4 Insensitive zone
6 General technical requirements
6.1 Scale and marking|| tt||JJG131—2004
6.2 Glass sleeve, temperature-sensing bulb and capillary tube…. Temperature-sensing liquid and temperature-sensing liquid column
6.4 Adjusting device
7 Control of measuring instruments
Verification conditions
Verification items·
7.3 Verification method
7.4 Processing of verification results…
7.5 Verification cycle
Appendix A Verification certificate (inside page) format of electric contact glass mercury thermometer Appendix B Electric contact glass mercury thermometer Notice of verification results of silver thermometer (inside page) Format Appendix C Evaluation of uncertainty in measurement results of temperature correction value of electric contact glass mercury thermometer (1)
(4)
(8)
1 Scope
JJG131-2004
Verification procedure for electric contact glass mercury thermometer This procedure is applicable to the initial verification, subsequent verification and in-use inspection of electric contact glass mercury thermometers (hereinafter referred to as thermometers) with various ranges of measurement range from -30℃ to 300℃. Fixed contact thermometers without scales can be calibrated or tested in accordance with this procedure.
2 References
References in this procedure
JB/T9264--1999 "Electric contact glass thermometer" When using this procedure, attention should be paid to using the current valid version of the above-mentioned referenced documents. 3 Terminology
Scale: A combination of a set of lines, numbers and measurement unit symbols (°C) on a thermometer to indicate the temperature value. Scale plate: A straight, colored (such as milky white) sheet used to print the scale inside the internal standard glass thermometer. Scale lines: Lines printed on a glass rod or scale plate to indicate the temperature value. Scale values: Numbers printed on a glass rod or scale plate to indicate the temperature value. Main scale: The scale of the measurement range. Auxiliary scale: The scale set for measuring the zero indication. Extension lines: Scale lines outside the upper and lower limits. Immersion line: A marking line used by a rod-type partial immersion thermometer to indicate the immersion position. Exposed liquid column: The part of the liquid column exposed outside the measured medium during the measurement of the thermometer. Intermediate bubble: The enlarged part of the inner diameter of the capillary tube, whose function is to accommodate part of the temperature-sensitive liquid in order to shorten the length of the capillary tube.
Safety bulb: The expanded part at the top of the capillary tube, which protects the thermometer from damage when the measured temperature exceeds a certain upper temperature limit of the thermometer.
4 Overview
4.1 Principle
The electric contact glass mercury thermometer measures temperature by utilizing the effect of the mercury in the transparent glass temperature-sensing bulb and the capillary tube expanding and contracting with the change of the measured temperature. There are two contacts in the thermometer, one on the upper end surface of the temperature-sensing mercury column and the other at any set position of the scale plate. When the ambient temperature changes, the temperature-sensing mercury column rises or falls, causing the two contacts to connect or disconnect. The electrical equipment can be controlled by the matching control device. 4.2 Structure
Thermometers are divided into two structures: adjustable and fixed. The common structural schematic diagrams of adjustable and fixed types are shown in Figures 1 and 2.
JJG131-2004
Figure 1 Adjustable thermometer
1-Adjusting magnet 2-Magnetic fixing screw; 3-Cover; 4 Wiring base; 5 Indicating nut; 6-Setting scale; 7-Adjusting screw; 8-Contact lead wire; 9-Tungsten wire; 10 Indicating scale; 11-Measurement capillary stop; 12-Scale plate; 13-Capillary fixing plug; 14-Temperature sensing bulb; 15-Lower body sleeve; 16-Capillary; 17-Safety bulb; 18-Upper body sleeve; 19-Flat tube; 20-Fan iron; 21-Signal line; 22 1. Wiring increaser 5. Metrological performance requirements
Indication stability
JJG131—2004
Figure 2 Fixed thermometer
1—Cover: 2. Wiring base: 3. Safety bulb: 4. Scale line: 5. Contact lead wire: 6. Measuring capillary: 7. Scale plate: 8. Upper body sleeve; 9. Capillary: 10. Lower body sleeve: 11. Capillary fixing plug; 12. Temperature sensing bulb: 13. Signal line: 14. Wiring terminal After the stability test, the rise value of the zero position of the thermometer should not exceed 1/2 of the scale value. Thermometers without zero auxiliary scales can measure the upper limit temperature indication. 3www.bzxz.net
5.2 Indication error
JJG131—2004
The allowable error limit of the indication of the thermometer is determined by the measurement range and scale value of the thermometer. The indication error of adjustable thermometers shall comply with the provisions of Table 1, and the indication error of fixed thermometers shall comply with the provisions of Table 2. When the range of the thermometer spans several temperature ranges in Table 1 and Table 2, the indication allowable error limit of the largest range shall be taken.
Table 1 Allowable error limits for indication of adjustable thermometers Upper or lower limit of the thermometer
Temperature range
-30~100
>100~200
>200~300
Upper or lower limit of the thermometer
Temperature range
>0~100
>100~200
>200~300
5.3 Action error
Graduation value
Table 2 Allowable error limits for indication of fixed thermometers Single-contact
Multi-contact
The maximum difference between the actual temperature value (determined by the standard thermometer) when the thermometer is connected and disconnected and the temperature indication of the thermometer contacts shall not exceed the allowable error limit for the indication of the thermometer. 5.4 Insensitive zone
The difference between the actual temperature when the thermometer is connected (determined by the standard thermometer) and the actual temperature when it is disconnected should not exceed 1/10 of the allowable error limit of the indication for the first calibration of the thermometer, and should not exceed 1/5 of the allowable error limit of the indication for the subsequent calibration of the thermometer.
6 General technical requirements
6.1 Scale and marking
6.1.1 The scale line of the thermometer should be perpendicular to the center line of the capillary. The scale line, measurement numbers and other markings should be clear and accurate, and the coloring should be firm and durable.
6.1.2 The spacing between two adjacent scale lines should be not less than 0.6mm, and the width of the scale line should not exceed 1/5 of the spacing between adjacent scale lines.
6.1.3 There should be no less than the allowable error limit of the indication of the thermometer outside the upper and lower limit temperature scale lines of the thermometer. The longitudinal displacement of the thermometer scale plate should not exceed 1/3 of the graduation value. The capillary should be in the center of the longitudinal axis of the scale plate and should not be significantly deflected. The distance between the capillary and the scale plate of the adjustable electric contact thermometer should not be greater than 3mm, and the distance between the capillary and the scale plate of the fixed electric contact thermometer should not be greater than 1mm. 6.1.5 The corresponding scale value (integer value) shall be marked every 10 to 20 scale lines, and the zero point and upper and lower limit temperatures of the thermometer shall also be marked with the corresponding scale value (except for the extended scale lines). Fixed thermometers shall be marked with the corresponding scale value at the joint.
6.1.6 The thermometer shall be marked with the manufacturing measuring instrument license mark, the symbol ℃ indicating degrees Celsius, the manufacturer's name or trademark, the year and month of manufacture, the product number, the working voltage and working current, etc. 6.2 Glass sleeve, temperature-sensing bulb and capillary tube
6.2.1 The glass sleeve shall be smooth and transparent. The glass sleeve and temperature-sensing bulb shall not have cracks or defects that affect the strength (such as internal stress, etc.). There shall be no defects or haziness that affect the reading within the scale range. 6.2.2 The glass sleeve shall be straight, uniform in thickness, and shall not have obvious bending. 6.2.3 The diameter of the temperature-sensing bulb of the thermometer shall not be larger than the diameter of the lower glass sleeve. 6.2.4 The capillary tube should be straight and its aperture should be uniform. When observing the thermometer from the front, the liquid column should have the maximum width. The connection between the capillary tube and the temperature-sensing bulb and the safety bulb should be arc-shaped and should not have necking phenomenon. The tube wall should be clean and free of impurities. 6.3 Temperature-sensing liquid and temperature-sensing liquid column
6.3.1 The temperature-sensing liquid should be pure and free of bubbles and other impurities. 6.3.2 The temperature-sensing liquid column should not be interrupted, should not flow by itself, should not have obvious stagnation or jumping when rising, and should not leave droplets on the tube wall when falling.
6.4 Adjustment device
6.4.1 The indicating nut of the adjustable electric contact thermometer should move evenly along the adjusting screw when the adjusting magnet rotates, and should not stagnate or loosen. The adjusting magnet should be reliably fixed. Metal parts should be smooth and rust-free. The cover, wiring base, and upper body sleeve should be fixed firmly and correctly. 6.4.2 The upper edge of the thermometer indicating nut and the end of the contact (tungsten wire) should be at the same indication on the upper and lower scale plates, and the difference should not be greater than one scale value. 6.4.3 The connection between the contact and the lead wire of the thermometer should be reliable. When the contact is turned on, the resistance value between the two terminals of the thermometer should not exceed 202.
7 Measuring instrument control
Measuring instrument control includes initial verification, subsequent verification and in-use inspection. 7.1 Verification conditions
7.1.1 See Table 3 for standard instruments and supporting equipment. 7.1.2 The ambient temperature is between 15℃ and 35℃. It is necessary to meet the conditions to prevent mercury leakage and pollute the environment. 7.2 Verification Items
The items for initial verification, subsequent verification and in-use inspection are shown in Table 4.7.3 Verification Methods
7.3.1 General Technical Requirements
Equipment Name
Second-class standard mercury
Thermometer
Constant temperature bath or
Constant temperature device
Ice point meter
Reading telescope
Glass polarizing stress meter
Steel ruler
DC ohmmeter
Temperature range
JJG131—2004
Table 3 Standards and supporting equipment
Technical performance
Measuring range: 30300
Working area||tt| |Horizontal temperature difference
-30~100
>100~300
Working area
Maximum temperature difference
Temperature stability
/℃-(10min）-1
Permissible error limit of indication 10
Standard instrument (other standards with accuracy level
not lower than the above requirements
may also be used)
Measurement zero point
Reading device
Glass stress inspection
Measurement spacing
Measurement of contact resistance, etc.
Note: 1. The working area in the constant temperature bath refers to the maximum range that the temperature sensing bulb of the standard thermometer and the thermometer under test can reach. 2. The maximum temperature difference refers to the temperature difference between any two points at different depths. Table 4 Verification Items
Verification Items
General Technical Requirements
Indication Stability
Indication Error
Action Error
Insensitive Zone
First Verification
Note: "+" in the table indicates that it should be calibrated, and "_" indicates that it is not necessary to calibrate. Subsequent Verification
Inspection in Use
7.3.1.1 For the first verification of thermometers, observe and measure with the naked eye, magnifying glass, steel ruler, glass polarizing stress meter, and DC ohmmeter. The thermometer should meet the requirements of 6.1 to 6.4 of this Regulation. 7.3.1.2 For subsequent verification of thermometers, the thermometer temperature sensing bulb and other parts should be checked for damage and cracks. If the temperature sensing liquid column has broken sections, bubbles, or droplets or color on the tube wall, it can be repaired and then calibrated.
7.3.2 Verification of indication stability
JJG131—2004
Keep the thermometer at the upper temperature limit for 15 minutes, take it out and cool it naturally to room temperature, and measure the zero position for the first time. Keep the thermometer at the upper temperature limit for 48 hours, take it out and cool it naturally to room temperature, and measure the zero position for the second time. Subtract the first zero position from the second zero position to get the zero point rise value, which shall meet the requirements of 5.1 of this regulation. Thermometers without zero point can directly measure the indication of their upper temperature limit according to the above method, and the difference between the two verification results shall meet the requirements of 5.1 of this regulation.
7.3.3 Verification of indication error
The verification result of indication error is given in the form of correction value. 7.3.3.1 The interval between the verification points of thermometers is specified in Table 5. When the verification points of the thermometer selected according to Table 5 are less than three, the lower limit, upper limit and any point in the middle shall be verified. Thermometers for subsequent verification can also be calibrated or tested according to user requirements. Thermometers for the first verification should be randomly inspected at any point between two specified verification points, and the indication error should comply with the provisions of Tables 1 and 2. 7.3.3.2 Temperature correction of exposed liquid column
The ambient temperature of the exposed liquid column of the thermometer during verification is specified to be 25°C. Under special conditions, the indication should be corrected according to formula (1) during verification.
At =kn(25-t)
Where At is the temperature correction value of the exposed liquid column, °C; k is the apparent expansion coefficient of the thermometer 0.00016, °C-1; the temperature corresponding to the length of the exposed liquid column on the thermometer, rounded to the nearest integer °C. (1)
Measure the ambient temperature of the exposed liquid column with the aid of an auxiliary thermometer (the auxiliary thermometer is placed at the lower 1/4 of the exposed liquid column, and pay attention to good thermal contact with the thermometer under test), °C. Table 5 Provisions for the interval between the thermometer calibration points
Division value
7.3.3.3 Verification method
Interval between calibration points
Insert the standard thermometer and the thermometer to be tested vertically into the thermostat. The constant temperature of the thermostat should not deviate from the specified calibration temperature by more than 0.20℃ (based on the standard thermometer). The thermometer should be stable in the constant thermostat for 10 minutes before reading. The line of sight should be perpendicular to the thermometer and read the highest point of the meniscus of the liquid column. The reading should be estimated to 1/10 of the graduation value.
Read the thermometer with a graduation value of 0.1℃ and 0.2℃ 4 times, and the thermometer with other graduation values ​​can be read twice. The reading order is standard→tested 1→tested 2tested n, and then return to the standard in the reverse order, calculate the arithmetic mean respectively, and obtain the indication of the standard thermometer and the thermometer to be tested. When the calibration scale value of the thermometer is 0.1℃, the second-class standard mercury thermometer should measure its zero position after each use. When it is found that the measured zero position has changed, the new indication correction value of each point should be calculated using formula (2).
New correction value = original certificate correction value + (zero position after upper limit temperature calibration in the original certificate - zero position after newly measured upper limit temperature calibration)
7.3.4 Verification of action error and insensitive zone (2)
7.3.4.1 Adjustable electric contact thermometers should be calibrated at any two points within the scale range, and fixed electric contact thermometers should be calibrated at all working contacts. 7.3.4.2 Verification method: Insert the thermometer into the constant temperature bath and connect the lead wire to the action indicating device. Slowly increase the temperature of the thermostat, and read the standard thermometer while the action indicator is turned on, which is the action temperature when it is turned on. Then slowly decrease the temperature of the thermostat, and read the standard thermometer while the action indicator is turned off, which is the action temperature when it is turned off. Repeat this process 4 times (a thermometer with graduations of 0.5°C, 1°C, 2°C, and 5°C can be repeated 2 times), and record the reading of the standard thermometer each time it is turned on and off. The heating and cooling speed of the thermostat should not exceed 0.01°C/min (for a thermometer with graduations of 0.1°C and 0.2°C) and 0.05°C/min (for a thermometer with graduations of 0.5℃, 1℃, 2℃, 5℃ thermometer).
The maximum difference between the action temperature of 4 times (or 2 times) connected and disconnected and the contact temperature on the scale plate (action error) shall meet the requirements of 5.3 of this regulation.
The difference between the action temperature of 4 times (or 2 times) connected and disconnected (insensitive zone) shall meet the requirements of 5.4 of this regulation.
7.3.5 Verification of connection resistance
Connect the connection terminals of the thermometer to the two test terminals of the DC ohmmeter and connect the contacts. Then shake the electric contact thermometer forward, backward, left and right. The maximum resistance measured shall not exceed 2002. 7.3.6 Data processing
See formula (3) for the data processing method.
x=(t+At)-(t+A0)
Wherein, x is the correction value of the thermometer under test, °C; t. is the indication of the standard thermometer, °C;
At is the correction value of the standard thermometer, °C;
t is the indication of the thermometer under test, °C;
△t is the temperature correction value of the exposed liquid column, °C, determined by formula (1). 7.4 Processing of verification results
Verification certificates or verification pass stamps shall be issued to thermometers that meet the requirements of this regulation after verification. A verification result notice shall be issued to thermometers that fail the verification, and the unqualified items shall be indicated. If the thermometer is calibrated or tested at certain temperature points according to the user's requirements, a calibration certificate or test certificate shall be issued. 7.5 Verification cycle
The verification cycle of the thermometer can be determined according to the usage conditions, generally not exceeding 1 year. 8
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