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National Metrology Verification Regulation of the People's Republic of China JJG310—2002
Pressure Thermometers
Filled System Thermometers
Promulgated on November 4, 2002
Implementation on May 4, 2003
Promulgated by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China JJG310-2002
Verification Regulation of
Filled System Thermometers
JJG310—2002
Replaces JJG310—1983
This regulation was approved by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China on November 4, 2002, and came into effect on May 4, 2003.
Responsible unit: National Technical Committee on Temperature Metrology Main drafting unit: Tianjin Institute of Metrology This regulation entrusts the National Technical Committee on Temperature Metrology to be responsible for interpreting this regulation Main drafters:
Wang Lixin
Liu Jingli
Participating drafters:
Shang Shisheng
Liu Chunwei
JJG310—2002
(Tianjin Institute of Metrology)||tt ||(Tianjin Institute of Metrology Technology)
(Tianjin Institute of Metrology Technology)
(Tianjin Institute of Metrology Technology)
(Tianjin Institute of Metrology Technology)
3 Metrology performance requirements
3.1 Indication error
Repeatability
Set point error
Switching difference
Alarm set point error
4 General technical requirements
Absolute Insulation resistance
5 Measuring instrument control
Verification conditions
Environmental conditions
Verification items
Verification methods
Verification result processing
Verification cycle
JJG310—2002
Appendix A Verification record format for pressure thermometers Appendix B Examples of uncertainty assessment for measurement results
1 Scope
JJG310 —2002
Verification Procedure for Pressure Thermometers
This procedure applies to the initial verification, subsequent verification and in-use inspection of circular scale steam pressure thermometers with a measuring range of -20℃～+200℃, circular scale gas pressure thermometers with a measuring range of -80℃~+600℃, and fully compensated liquid pressure thermometers (hereinafter referred to as thermometers), and additional mechanical electric contact pressure thermometers (hereinafter referred to as electric contact thermometers).
2 Overview
Pressure thermometers work on the principle that the volume or pressure of the working substance inside a closed system changes with temperature, as shown in Figure 1. The closed system of the instrument consists of a temperature bulb, a capillary tube and an elastic element. The temperature bulb is filled with a working medium. When measuring the temperature, the temperature bulb is inserted into the measured medium. Affected by the temperature of the medium, the volume or pressure of the working medium inside the temperature bulb changes. This change is transmitted to the elastic element (such as a spring tube) through the capillary tube. The elastic element deforms, and the free end is displaced. With the help of the transmission mechanism, the pointer is driven to indicate the temperature value on the dial. Dial
Elastic element
-Transmission mechanism
Capillary
Working substance
Figure 1 Typical structure diagram of pressure thermometer
3 Metrological performance requirements
3.1 Indication error
The relationship between the maximum allowable error of the thermometer indication and the accuracy grade shall comply with the provisions of Table 1. 3.2 Hysteresis
The hysteresis of the thermometer shall not be greater than the absolute value of the maximum allowable error of the indication. 3.3 Repeatability
The repeatability of the thermometer shall not be greater than 1/2 of the absolute value of the maximum allowable error of the indication.1
Accuracy grade
JJG310-—2002
Table 1 Accuracy grade and maximum allowable error
Maximum allowable error (% of range)
Note: The accuracy grade of the steam pressure thermometer refers to the last 2/3 of the measuring range. 3.4 Set point error
The set point error of the electric contact thermometer shall not exceed 1.5 times the maximum allowable error of the indication. 3.5 Switching difference
The switching difference of the electric contact thermometer shall not be greater than 1.5 times the absolute value of the maximum allowable error of the indication. 3.6 Alarm set point error
The alarm set point error of the fully compensated liquid electric contact pressure thermometer shall not exceed 1.5 times the maximum allowable error of the indication.
4 General Technical Requirements
4.1 Appearance
4.1.1 The protective glass or other transparent materials used for the thermometer head should be transparent and should not have defects or damage that prevent correct reading.
4.1.2 The various components of the thermometer should be firmly assembled and should not be loose, rusty, or have significant corrosion or peeling of the anti-corrosion layer.
4.1.3 The scale, numbers and other marks on the thermometer dial should be complete, clear and accurate. The pointer should extend within 1/4~3/4 of the shortest scale line of the scale, and the width of the pointer tip should not exceed the width of the shortest scale line of the scale. 4.1.4 The distance between the pointer of the thermometer and the dial plane should be within the range of (1~3) mm. 4.1.5 The thermometer dial should be marked with the symbol "℃" of the international temperature scale Celsius, the manufacturer's name (or factory logo), model and factory number, accuracy grade, year and month of manufacture, and the mark and number of the measuring instrument manufacturing license. The electric contact thermometer should also be marked on the dial or shell: the rated power of the contact, the maximum voltage of the contact, the maximum working current of AC or DC, and the "Yan" mark of the ground terminal.
4.1.6 The thermometer should have a seal position. 4.1.7 The pointer of the thermometer should move smoothly during the calibration process, and there should be no obvious jumping or stagnation (the pointer of the steam pressure thermometer is allowed to have slight jumping in the part across the room temperature). 4.2 Insulation resistance
When the ambient temperature is (15~35)℃ and the relative humidity is 45%~75%, the insulation resistance between the output terminals of the electric contact thermometer and between the output terminals and the grounding terminal shall not be less than 20M2. 2
5 Measuring instrument control
5.1 Verification conditions
5.1.1 Standard instrument:
JJG310-2002
The standard instrument for verifying the thermometer can be selected according to the measurement range. The second-class standard mercury thermometer, the standard mercury-based thermometer or other standards that meet the accuracy requirements can be selected. 5.1.2 Supporting equipment:
The technical performance of the thermostat bath is shown in Table 2.
Table 2 Technical performance requirements of the thermostat bath
Name of the thermostat bath
Alcohol low-temperature bath
Constant overflow bath
5.1.2.2 Ice point bath
Using temperature range/℃
-80~room temperature
Room temperature~95
95~300
300~600
Reading magnifier (5~10) times.
5.1.2.4 Reading system.
5.1.2.5500V insulation resistance meter.
5.2 Environmental conditions
5.2.1 Calibration environment temperature: 15℃~35℃; humidity: not more than 85%RH.
Horizontal temperature difference in working area/℃
Maximum temperature difference in working area/℃
5.2.2 The environmental conditions for the use of standard instruments and electrical measuring equipment should meet the corresponding specified conditions. 5.3 Calibration items
The calibration items of thermometers are shown in Table 3.
Table 3 Verification Items
Verification Items
Indication Error
Repeatability
Set Point Error
Switching Difference
Insulation Resistance
First Verification
Subsequent Verification
Note: "+" indicates that verification is required, "_" indicates that verification is not required, and verification can also be performed according to user requirements. Verification during Use
5.4 Verification Method
5.4.1 Appearance Inspection:
JJG310—2002
Visual inspection of the thermometer shall comply with the provisions of 4.1 of this Regulation. Defects that do not affect the use and correct reading of the thermometer are allowed during subsequent verification and inspection during use. 5.4.2 Insulation resistance:
Use an insulation resistance meter with a rated DC voltage of 500V to measure the insulation resistance between the output terminals of the electric contact thermometer and between the output terminals and the grounding terminal. It shall comply with the provisions of 4.2 of this regulation. 5.4.3 Indication error:
5.4.3.1 The thermometer head shall be installed vertically before calibration. 5.4.3.2 During calibration, the temperature bulb of the thermometer must be fully immersed, and the immersion of the extension tube shall not be less than 1/3~2/3 of the tube length. 5.4.3.3 The height difference between the meter head and the temperature package should not be greater than 1m. 5.4.3.4 For the first calibration of the thermometer, the calibration points should be evenly distributed over the entire measuring range (must include the upper and lower limits of measurement), and shall not be less than 4 points. Thermometers with a 0℃ point should include the 0℃ point. 5.4.3.5 When the thermometer is subsequently calibrated and inspected during use, the calibration points should be evenly distributed over the entire measuring range (must include the upper and lower limits of measurement), and shall not be less than 3 points. Thermometers with a 0℃ point should include the 0℃ point. 5.4.3.6 The calibration of the thermometer should be carried out point by point in the positive and negative strokes in the direction of the upper or lower limit, and only single-stroke calibration should be carried out when measuring the upper and lower limit values. 5.4.3.7 When reading the indication of the thermometer being tested, the line of sight should be perpendicular to the degree plate, and when reading with a magnifying glass, the line of sight should pass through the center of the magnifying glass. When reading, the reading should be estimated to 1/10 of the scale value. 5.4.3.8 When checking at 0℃, insert the thermometer's temperature bulb into an ice point tank or a constant temperature tank containing an ice-water mixture, and read the value after the indication stabilizes. The maximum error of the thermometer indication shall comply with the provisions of 3.1 of this regulation. 5.4.3.9 When checking at other points, insert the temperature bulb of the thermometer to be checked and the standard thermometer into the constant temperature tank, and read the value after the indication stabilizes. When reading, the temperature of the tank shall not deviate from the temperature of the calibration point by more than ±0.5℃ (based on the standard thermometer), and record the indications of the forward and reverse strokes of the standard thermometer and the thermometer to be checked respectively. During the reading process, when the tank temperature does not exceed 300℃, the change of the tank temperature should not be greater than 0.1℃, and when the tank temperature exceeds 300℃, the change of the tank temperature should not be greater than 0.5℃. When the electric contact thermometer is checking the indication, the upper and lower limit setting pointers should be placed outside the upper and lower limits respectively. The maximum error of the thermometer indication shall comply with the provisions of 3.1 of this Regulation. 5.4.4 Stability of pointer movement:
The inspection of the stability of pointer movement shall be carried out simultaneously with the indication verification. When the temperature rises or falls, the movement of the pointer shall comply with the provisions of 4.1.7 of this Regulation.
5.4.5 Hysteresis:
The verification of the thermometer hysteresis shall be carried out simultaneously with the indication verification (except for the measuring limit and lower limit). The absolute value of the difference between the positive and reverse stroke errors at the same verification point is the thermometer hysteresis, which shall comply with the provisions of 3.2 of this Regulation. 5.4.6 Repeatability:
In the positive or reverse stroke indication verification of the thermometer, the indication verification shall be repeated multiple times (at least three times) at each verification point. The absolute value of the maximum difference between the indications of the same stroke at each point is calculated as the repeatability of the thermometer, which shall comply with the provisions of 3.3 of this Regulation.
5.4.7 Set point error, switching difference and alarm set point error: 4
JJG310—2002
5.4.7.1 The first calibration of the electric contact thermometer should be carried out at least 3 set points within the measurement range (except the upper and lower limits of measurement), and the set points should be basically evenly distributed on the long scale line. 5.4.7.2 The subsequent calibration and in-use inspection of the electric contact thermometer are allowed to be carried out at only one set point within the measurement range (except the upper and lower limits of measurement), and the set point should be on the long scale line. 5.4.7.3 Insert the temperature package of the electric contact thermometer to be tested and the standard thermometer into the constant temperature bath, and connect the terminals of the electric contact thermometer to be tested to the signal circuit, as shown in Figure 2. Then slowly and evenly change the temperature of the constant temperature bath (the temperature change rate should not exceed 1℃/min) to make the contacts produce a switching action of closing and opening (the signal circuit is connected or disconnected). At the moment of action, the reading of the standard thermometer is the upper switching value of the positive stroke of the contact or the lower switching value of the reverse stroke. 5.4.7.4 The average of the upper switching value and the lower switching value is the switching median value. The difference between the switching median value and the temperature indicated by the set pointer of the tested electric contact thermometer is the setting point error, which shall comply with the provisions of 3.4 of this regulation; the absolute value of the difference between the upper switching value and the lower switching value is the switching difference, which shall comply with the provisions of 3.5 of this regulation. The setting point error and the switching difference are calibrated once for the closing and opening of the contact at the same setting point. 5.4.7.5 The electric contact fully compensated liquid pressure thermometer can only perform the alarm setting point error calibration according to the user's requirements, that is, only perform the upper switching value of the positive stroke of the contact or the lower switching value of the reverse stroke of the contact. The difference between the upper switching value or the lower switching value and the temperature indicated by the set pointer of the tested electric contact thermometer is the alarm setting point error, which shall comply with the provisions of 3.6 of this regulation.
Electric contact thermometer
Figure 2 Signal circuit
5.5 Verification result processing
5.5.1When a second-class standard mercury thermometer or a standard mercury-based thermometer is used as a standard instrument, the indication error of the thermometer to be tested is calculated according to formula (1):
y=t- (+A)
Wherein: y is the indication error of the thermometer to be tested, ℃; t is the indication of the thermometer to be tested, ℃;
t is the indication of the standard instrument, ℃;
A is the correction value of the standard instrument, ℃.
5.5.2For thermometers that pass the verification according to the requirements of this regulation, a verification certificate shall be issued; for thermometers that fail the verification, a verification result notice shall be issued, and the unqualified items shall be noted. 5.6 Verification cycle
The verification cycle of the thermometer shall be determined according to the specific usage conditions and shall not exceed 1 year at most. 5
Appendix A
Inspection unit:
Measuring range:
Model specification:
Name of standard instrument:
JJG310—2002
Pressure thermometer calibration record format
Manufacturer:
Accuracy grade:
Standard instrument number:
Nominal temperature of calibration point/℃
Standard instrument reading/℃
Positive stroke reading! ℃
Standard instrument reading/℃
Indication verification
Set point error
Difference and switching
Difference verification
Appearance inspection:
Verification basis:
Verification conclusion:
Ambient temperature:
Verifier:
Reverse stroke reading/℃
Forward stroke error/℃
Reverse stroke error/℃
Hysteresis/℃
Upper contact
Set point temperature/℃
Switching median value/℃
Set point error/℃
Switching difference/℃
Upper switching value/℃||tt ||Lower switching value/℃
Insulation resistance:
Verification certificate number:
Humidity:
Verifier:
Factory number:
Graduation value:
Standard instrument certificate number:
Lower contact
Upper switching value/℃
Lower switching value/℃
Appendix B
B.1 Overview
JJG310—2002
Example of uncertainty assessment of measurement results
According to the verification method of this regulation, the second-class standard mercury thermometer and the pressure thermometer to be tested are placed in a constant temperature bath together and the comparison method is used for verification. Due to the different temperature field conditions in the constant temperature bath, the temperature difference is usually large at 300℃. A pressure thermometer with a measuring range of 0℃~300℃, an accuracy level of 2.5, and a minimum graduation value of 5.0℃ is calibrated at 300℃. The indication error of the thermometer at 300℃ can be obtained by calculation, and uncertainty analysis is performed.
Mathematical model
y=t-(t+A)
Where: y——indication error of pressure thermometer at 300℃, ℃; t——indication of pressure thermometer during measurement, ℃; t——indication of second-class standard mercury thermometer, ℃; A——correction value of second-class standard mercury thermometer, ℃. B.3 Sensitivity coefficient
c,=aylat=1
c2=aylat'=-1
C =ylaA=-1
B.4 Evaluation of standard uncertainty
B.4.1 Evaluation of standard uncertainty u(t) of input quantity t. Main sources of standard uncertainty of input quantity: B.4.1.1 Standard uncertainty u(t,) introduced by the estimated indication of the pressure thermometer under test. Since the indication of the pressure thermometer is estimated to 1/10 of its minimum scale value, i.e. 0.5°C, the half width of the error interval caused is 0.5/2=0.25°C, and its distribution is uniform, with a coverage factor of k=/3. Its standard uncertainty is u(t,)=0.25//3=0.14°C, and the relative uncertainty of its estimated value uncertainty is about 10%, then the degree of freedom v(t)=(10%)-2/2=50.
B.4.1.2 The standard uncertainty u(t2) introduced by the repeatability of the indication of the pressure thermometer under test is evaluated using the standard uncertainty of type A.
For three pieces with a measuring range of 0℃~300℃, an accuracy level of 2.5, and a minimum division value of 5.The 0℃ pressure thermometer performs 10 repetitive measurements at 0, 100, 200, and 300℃ respectively (all on the positive stroke), thus obtaining 12 groups (a total of 120) of data, and then calculates the experimental standard deviation s for each group, that is: S, = 7
JJG310—2002
0.03℃$2=0.03℃$=0.02℃$4=0.07℃s5=0.14℃S=0.03℃
Sg=0.04℃8g=0.02℃510=0.06℃s1=0.04℃S12=0.04℃
·So:
Degrees of freedom:
u(t,）=
（≥s2）/12 =0.06℃
With (t2)=12×（10-1）=108
Because, u(t,) and u(t) are independent of each other, so: u(t)=u(t)+u(t)=0.15℃
Degrees of freedom:
u'(t)u'(t2)
B.4.2 Evaluation of standard uncertainty u() of input quantity t37=0.05℃www.bzxz.net
B.4.2.1 The indication of the second-class standard mercury thermometer is estimated to introduce standard uncertainty u(t). The indication of the second-class standard mercury thermometer should be estimated to 1/10 of the minimum graduation value, that is, 0.01℃. The half-width of the error interval caused is 0.005℃. Because the value is relatively small, it can be ignored. Then u()=0B.4.2.2 The standard uncertainty u(t,) introduced by the temperature fluctuation of the thermostatic bath is evaluated by the Class B standard uncertainty. The temperature fluctuation of the thermostatic bath during the reading process does not exceed 0.1°C, and its distribution is the inverse chord distribution, with a coverage factor of k=2. Its standard uncertainty is u(t)=(0.12)=0.04°C, and the relative uncertainty of its estimated value uncertainty is about 20%. Then the degree of freedom (t2)=(20%)-2/2=12. B.4.2.3 The standard uncertainty u(t3) introduced by the non-uniformity of the temperature field of the thermostatic bath is evaluated by the Class B standard uncertainty. The maximum temperature difference of the temperature field of the thermostatic bath at 300℃ does not exceed 0.2℃, and its distribution is uniform, k=/3, and its standard uncertainty is:
α(t,） =(0:2/2) =0.06℃
The relative uncertainty of the uncertainty of its estimated value is about 20%, so the degree of freedom (t,) = (20%)-2/2 = 12. Because u(t,) and u(t) are independent of each other, so: u(t) = Nu(t) + u(t) = 0.07℃
） = 19
v(t) = -
B.4.3 Evaluation of the standard uncertainty u(A) of input quantity A B.4.3.1 The standard uncertainty introduced by the correction value of the second-class standard mercury thermometer is evaluated using the Class B standard uncertainty. From the verification procedure of second-class standard mercury thermometers, it can be known that the expanded uncertainty of the indication verification result at 300°C is 0.06°C, the confidence probability is 99%, the coverage factor = 2.58, and its standard uncertainty u (A) = 0.06°C/2.58 = 0.02°C. Degrees of freedom → 8
B.4.3.2 The standard uncertainty component introduced by the second-class standard mercury thermometer when it is used without zero correction is 8
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