Some standard content:
National Metrology Verification Regulation of the People's Republic of China JJG274-2007
Double Tube Mercury Barometer
Double Tube Mercury BarometerIssued on 2007-06-14
Implementation on 2007-12-14
The General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China issued JJG274—2007
Verification Regulation of
DoubleTubeMercuryBarometer
JJG274—2007
Replaces JJG274—1981
This regulation was approved by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China on June 14, 2007, and came into effect on December 14, 2007.
Responsible unit: National Pressure Measurement Technical Committee Main drafting unit: Shanghai Meteorological Instrument Testing and Metrology Center Participating drafting unit: Changchun Meteorological Instrument Factory This regulation is entrusted to the National Pressure Measurement Technical Committee to be responsible for the interpretation of this regulation Main drafter:
JJG274—2007
Taidai Shuiying
Xiong Jiansheng (Shanghai Meteorological Instrument Testing and Metrology Center) Participating drafter:
Chen Qihuan (Shanghai Meteorological Instrument Testing and Metrology Center) Scope·
3 Metrological performance requirements
3.1 Requirements for indication correction value
JJG274—2007
3.2 The maximum indication value after correction Maximum allowable error 4 General technical requirements.
4.1 Appearance·..
4.2 Other requirements·
5 Control of measuring instruments:
5.1 Verification conditions
Verification items
Verification methods
Processing of verification results
5.5 Verification cycle
Appendix A Calculation method of mercury content in mercury cup Appendix B
Appendix C
Appendix D|| tt||Appendix E
Format of calibration record sheet for comparison of indicated values of double-tube mercury pressure GaugesPrecautions for calibration and data processingFormat of inner pages of calibration certificate
Format of inner pages of calibration result notification
(1)
1Scope
JJG274—2007
Verification procedure for double-tube mercury pressure gauges
This procedure applies to the initial calibration, subsequent calibration and in-service inspection of double-tube mercury pressure gauges. 2 Overview
Double-tube mercury pressure gauge (hereinafter referred to as double gauge) is a small instrument used to measure the pressure in the pressure device. The double-tube gauge uses the gravity and pressure of the mercury column in the vacuum tube with good vacuum degree. It can also measure atmospheric pressure. The pressure is measured based on the principle that the gravity of the mercury column in the tube and the external force (the pressure in the pressure device or the sum of the atmospheric pressure) are balanced. The structure of the double-tube gauge is siphon trough type. It is mainly composed of two glass inner tubes (one of which is called vacuum tube and the other is called pressure tube) and its outer jacket mercury trough, mercury rod zero point indicator ring. Its measurement range is generally 0hPa~1070hPa, which requires 13 metrological performance requirements
3.1 For indicator Requirements for value correction value
The operating temperature of the main scale, vernier and its adjustment mechanism is -15℃ to
45℃.
The indication correction value obtained by comparative verification of the indication value of the double-tube meter shall not exceed ±0.40hPaS
Maximum allowable error after repair
3.2 After the double-tube meter passes the first verification or subsequent verification or the inspection in use, after the indication value is corrected during the service period, the maximum allowable error within the range of
107ahPa is ±0.30hPa, and the maximum allowable error within the range of 450hPa to 1
is ±0.50hPaB
General technical requirements
4. 1 Appearance
4.1.1 The two inner tubes should be straight
smooth, with consistent thickness from top to bottom, and should not have cracks or other defects that affect the strength. There should be no defects such as air threads, bubbles, scratches, ripples, etc. that affect the readings in the measuring section. 4.1.2 The two outer tubes should be straight, smooth, and free from defects such as dents and lacerations. The front and rear slots should be parallel, neat, and of uniform width: the center lines of the two slots and the axis of the outer tube should be in the same plane. 4.1.3 The scale lines of the main scale and the vernier scale should be perpendicular to the edge of the outer tube slot of the pressure pipe. When any scale line of the vernier scale is aligned with any scale line of the main scale, the two scale lines should be connected in a straight line: all scale lines and corresponding engraved numbers should be clear, uniform, and firmly filled with color.
4.1.4 Front and rear reference of the vernier scale support The edge should be flat and on the same level as the zero scale of the vernier scale, and perpendicular to the outer sleeve axis of the pressure tube.
4.1.5 All parts in contact with mercury should be tightly combined and there should be no mercury leakage. 4.1.6 The connecting hose between the mercury tank and the bottom of the mercury cup should be soft. 1bzxz.net
JJG274—2007
4.1.7 All parts should be installed correctly and firmly, and there should be no looseness, deformation or other defects that affect the use. For new double-tube meters, the protective layer of each part should be firm, uniform and smooth, and there should be no falling off, rust and other phenomena. 4.1.8 The hanging plate should be light, firm and crack-free; the surface should be flat, smooth and uniform in color, and the corresponding part of the scale and zero point indicator should have a white lining to facilitate the adjustment of the mercury surface. 4,1.9 The auxiliary thermometer should be installed correctly and firmly, and should be qualified after verification and used within the verification period. 4.1.10 The nameplate should clearly indicate the instrument name, model specifications, manufacturer name, year of manufacture, factory number, etc.
4.2 Other requirements
4, 2.1 The vacuum tube and pressure tube should be securely fixed to the center of the corresponding outer tube with cork, and there should be no looseness. 4.2.2 The lower edge of the zero point indicator ring on the vacuum tube and the zero scale line on the outer tube of the pressure tube should be on the same horizontal plane.
4.2.3 After the vacuum tube and pressure tube are filled with mercury, the contact part between the mercury and the inner wall of the glass inner tube should not have defects such as bubbles, stains, impurities that affect the reading. When the mercury moves in the glass inner tube, there should be no stickiness and residual mercury drops. When the mercury surface is adjusted in an upward trend, the top of the mercury column in the glass inner tube should be a clean and obvious convex meniscus, and symmetrical to the axis of the outer tube.
4.2.4 The distance between the top of the vacuum tube and the bottom edge of the zero indicator ring must be greater than 50mm. 4.2.5 There should be a good vacuum degree in the vacuum tube. 4.2.6 The vernier scale adjustment mechanism should: its spiral sleeve can move flexibly and smoothly within the measuring range, without blocking, loosening, and scratching the outer sleeve surface; the spiral sleeve can be firmly fixed at any position of the main scale with the help of the brake; adjusting the fine-tuning nut can flexibly and smoothly adjust the position of the vernier scale. 4.2.7 The mercury cup must be filled with an appropriate amount of mercury. When the vent is closed, mercury must not leak. 4.2.8 The adjusting screw connected to the mercury cup should be able to rotate smoothly and flexibly when adjusting the lifting and lowering. 5 Measuring instrument control
Measuring instrument control includes initial calibration, subsequent calibration and inspection during use. 5.1 Verification conditions
5.1.1 Environmental conditions
5.1.1.1 The room shall not be exposed to direct sunlight and the air shall not flow too much. 5.1.1.2 The verification location shall not be set near a heat source and shall be selected in a place with less vibration. 5.1.2 Standard instrument
The standard instrument for verifying the double-tube meter is a second-class standard mercury barometer or other pressure measurement standard instrument with equivalent accuracy. 5.1.3 Auxiliary equipment
5.1.3.1 Indication comparison verification cabinet: The installation shall be firm and vibration-free. There shall be a hanging plate, a hook fixing frame, a track ring, etc. for hanging the double-tube meter in the cabinet, and they shall be firmly installed. There shall be a cold light source or a low-power lighting device for the adjustment and reading position.
5.1.3.2 Other tools: measuring tools such as a square, a ruler or a vernier caliper. 5.2 Verification items
The verification items are shown in Table 1.
Verification items
Technical requirements
Other requirements
Indication comparison verification
Note: "+" indicates the items to be inspected.
5.3 Verification method
JJG274—2007
Table 1 List of verification items
First verification
5.3.1 Visual inspection of appearance in accordance with the requirements of Article 4.1. +
Subsequent verification
5.3.2 General technical requirements 4.See Table 2 for the inspection methods of each item in Article 2. Table 2 General Technical Requirements Inspection Methods of Each Item in Article 4.2 Clause
Inspection Method
Press the vacuum tube and pressure tube with your fingers to determine whether there is any looseness. Inspection during use
Use a right-angled edge of the square ruler to press against the left side of the corresponding outer sleeve slot of the zero indicator ring, and the other right-angled edge to press against the lower edge of the zero indicator ring, and observe that the horizontal direction of the right-angled edge should not deviate significantly from the zero scale line on the corresponding outer sleeve of the pressure tube
Adjust the adjusting screw connected to the mercury cup to move the mercury surface up and down, and observe whether there are bubbles, stains, impurities, etc. that affect the reading at the contact part between the mercury and the inner wall of the glass inner tube. Observe whether the mercury is sticky or has residual mercury drops during its movement; adjust the mercury surface to be tangent to the lower edge of the zero indicator ring on the vacuum tube in an upward trend, and then adjust the vernier scale on the pressure tube to make it tangent to the mercury surface, and observe whether the tops of the mercury columns in the two glass inner tubes are clean convex meniscuses and whether the light transmission angles on both sides are consistent; use a clip to clamp the double tubes in their original positions under the lifting ring cap, and then remove the lifting ring cap, and measure with a ruler or a vernier caliper.
1. Slowly tilt the double-tube gauge to the other side of the mercury cup, so that the mercury column lightly hits the top of the vacuum tube. If there is a crisp metallic sound, it indicates that the vacuum degree is good, otherwise a bubble check should be performed. If you are not proficient in this method, you can directly use the bubble inspection method
2. Bubble inspection method: clamp the double tube with a clip under the ring cap, remove the ring cap, and then slowly tilt the double tube meter to the other side of the mercury cup. After the mercury just reaches the tube, continue to tilt the tube top to drop the vertical height by another 16cm, and measure the bubble on the tube top. Requirements: For the first calibration, the bubble diameter shall not be greater than 1mm; for subsequent calibration and in-use inspection, the bubble diameter shall not be greater than 1.5mm. If a new vacuum tube is replaced, it should meet the requirements of the first calibration. Slowly move the vernier within the scale range to check whether it is flexible and stable, and whether there is any obstruction, looseness or scratches on the outer tube surface. Tighten the brake at any position of the main scale to check whether it can be firmly fixed, and adjust the fine-tuning nut to check flexibility and stability. 3. JJG274—2007. Table 2 (continued). Inspection method. 1. Under normal pressure, adjust the adjusting screw connected to the mercury cup to make the mercury surface tangent to the lower edge of the zero point indicator ring of the vacuum tube in an upward trend. Then remove the vernier on the pressure tube, and use one right-angled side of the square ruler to lean against the side of the outer tube of the pressure tube close to the mercury cup. The other right-angled side of the square ruler is flush with the top of the mercury column of the pressure tube. The air pressure value at that time can be read from the main scale (rounded to the integer). At the same time, the right-angled edge is horizontally directed to the mercury cup, that is, the height of the mercury surface in the mercury cup. This height is measured from the bottom of the mercury cup and should not exceed the value of 10mm calculated by the method in Appendix A based on the atmospheric pressure reading at that time. 2. Tighten the screw that closes the through hole on the mercury cup and cut the mercury cup inverted to observe whether there is mercury leakage.
Adjust the adjusting screw connected to the mercury cup and check whether it can rotate smoothly and flexibly.
5.3.3 Indication comparison verification
5.3.3.1 Indication comparison verification is to use a standard instrument and a double-tube meter in the indication comparison verification cabinet to compare the indication under atmospheric pressure. A standard instrument can only compare and verify three double-tube meters at most at the same time.
5.3.3.2 The indication ratio verification must be carried out after the standard instrument and the double-tube meter are vertically suspended (the groove part shall not deviate from the vertical line by more than 1mm) and stabilize for more than 4 hours.
5.3.3.3 At the beginning of the indication ratio verification, the reading of the auxiliary thermometer shall be carried out first, and the value shall be estimated to the tenth place and recorded to check whether there is any abnormality in the auxiliary thermometer. If there is an abnormality, the cause shall be found out and eliminated or replaced with a normal auxiliary thermometer.
5.3.3.4 The effective comparison readings of each double-tube meter shall not be less than 5 times, and the interval time shall not be less than 1 hour.
Complete,
each reading shall be completed by one person
each reading
5.3.3.5 The entire indication comparison verification process shall be completed by two or more people. When reading, the silver surface should be kept upward
, and the changing trend should be tangent to the lower edge of the zero indicator ring and the cursor. Then adjust the cursor
, and adjust the zero position first. The odd readings in each reading should be adjusted in the order of the standard instrument and the double-tube meter. The stop and sell numbers should be adjusted in the opposite order. It is required to be fast and accurate. The whole process time should not exceed 4. After adjusting the unified reading, estimate
to the percentile and record it.
5.3.3.6 Eliminate abnormal values: When the difference between the readings of the standard instrument and the double-tube meter and the average value exceeds 0.15hPa, the reading of the double-tube meter that exceeds the tolerance is discarded and re-measured. A maximum of two re-measurements can be made. 5.3.4 Data processing
The format of the indication comparison verification record table is as follows:
5.3.4.2 The indication correction value is calculated using the formula (10): C
Where: C,
The indication correction value of each double-tube meter under inspection, hPa; QG
The difference between the standard instrument indication value and the double-tube indication value for each reading, hPaAp
The number of comparison readings (not less than 5 times): The indication correction value of the standard instrument, hPa.||tt ||Among them,
JJG274—2007
rounded to percentile according to the rounding rules.
5.3.5When the standard instrument is not a second-class standard mercury barometer, the relevant precautions in the verification and data processing are shown in Appendix C5.4 Processing of verification results
According to the requirements of this regulation, a verification certificate shall be issued to the qualified double-tube meter after verification; a verification result notice shall be issued to the unqualified double-tube meter after verification, and the unqualified items and contents shall be noted. SAOAN IID
5.5 Verification cycle
Determined by the use environment and the frequency of use, generally not more than 3 years. The verification cycle of the double-tube meter is based on its
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Appendix A
JJG274—2007
Calculation method of mercury in the mercury cup
The mercury in the mercury cup is used to supplement the mercury required by the pressure tube during operation. Under normal pressure, the height H (mm) from the outer bottom of the mercury cup to the mercury liquid level should be calculated according to formula (A.1): 4h.元r2
In the formula: h-
the atmospheric pressure reading under normal pressure, hPa;
3/4 the conversion value of one hundred Pascals (hPa) into the height of the mercury column (mm); the radius of the inner diameter of the pressure tube (the design value is 4.75mm); R-the radius of the inner diameter of the mercury cup (the design value is 17.2mm); 35
-the amount of mercury in the mercury cup, in addition to the amount of mercury required by the pressure tube, should also have a 30mm high mercury surplus, and the thickness of the bottom cover and the gasket is 5mm, so it is 35mm. Substituting R=17.2mm and r=4.75mm into formula (A.1), we get H=0.0572h+35
Using the atmospheric pressure value under normal pressure, use formula (A.2) Calculate the amount of mercury in the mercury cup and express it in terms of the height H from the bottom of the mercury cup to the mercury surface.
Appendix B
Month/Day
Tested meter
Tester:
JJG274—2007
Format of comparison calibration record of double-tube mercury pressure indication value Standard instrument:
Calibration time
Attached temperature table
Temperature/℃
Average pressure difference value/hPa
Instrument correction value of standard instrument/hPa
Indication correction value of tested meter/hPa
Specification model
Manufacturer name
Name of inspection unit||tt| |Pressure reading
Inspected meter: double-tube mercury pressure gauge
Certificate number:
Attached temperature gauge
Temperature/C
Verifier:
Pressure reading
Pressure difference
Appendix C
JJG274-2007
Precautions in verification and data processing
When conducting comparative verification of the indication of a double-tube gauge, if the standard instrument is not a second-class standard mercury barometer but other standard instruments, its adjustment and reading shall be carried out in accordance with the technical requirements of the corresponding standard instrument for adjustment and reading. At the same time, when processing data, it is necessary to pay attention to whether the meaning of the reading of the corresponding standard instrument is consistent with that of the double-tube gauge being inspected to determine the method of data processing. If the corresponding standard instrument is not the actual local pressure value at that time, then the pressure value of each reading of the double-tube meter under test after temperature and gravity correction should be subtracted from this value to obtain the pressure difference of each reading (in this case, when reading each time in the indication comparison verification, the auxiliary temperature gauge of the double-tube meter under test should be read at the same time. The temperature should be corrected to the nearest tenth according to the correction rules, which is the double-tube value under test). Then calculate the average value of the pressure values of each reading, and the "pressure reading" and "pressure difference" of the meter should be recorded in the meter's indication correction value. At the same time, in the system comparison verification, the "pressure value after temperature and gravity correction" should be added between the two columns of "tested value" in the record table.
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