How to calculate the pressure gauge as qualified

Routine verification items and regulations of pressure gauge

1, visual inspection

1. 1 pressure gauge parts shall be firmly assembled without looseness.

1.2 The newly manufactured pressure gauge shall be flat and smooth without obvious peeling.

1.3 the pressure gauge should have a safety hole, and the safety hole should have a dustproof device. (The measured medium is not allowed to overflow the off-balance-sheet pressure gauge unless)

1.4 pressure gauge dial shall have the following marks, manufacturers or trademarks; Product name; Marks and numbers of manufacturing licenses of measuring units and digital measuring instruments, and vacuum meters should have the words "-"or "negative", accuracy grade and factory number.

For the reading part of 1.5, the glass of the instrument shall be colorless and transparent, and there shall be no defects that hinder the reading. The dial should be smooth and bright, and all signs should be clearly identifiable.

1.6 The indicating end of the pointer should cover 1/3~2/3 of the shortest scale line length, and the width of the indicating end of the pointer should not be greater than that of the scale line.

The accuracy grades of 1.7 are 1,1.6,2.5,4.

1.8 For the pressure gauge with stop pin, the pointer should be close to the stop pin when there is no pressure or vacuum, and the "shrinkage" should not exceed the allowable error value specified in table 1; For pressure gauges without stop pins, the pointer should be at the zero position when there is no pressure or vacuum, and the zero position should not exceed twice the absolute value of the allowable error specified in table 1.

2. Measuring instruments

2. 1 The absolute value of the allowable error of the etalon shall not be greater than 1/4 of the absolute value of the allowable error of the detected pressure gauge.

2.2 The standard instrument can be spring tube precision pressure gauge and vacuum gauge, piston pressure gauge and piston vacuum pressure gauge.

2.3 Auxiliary equipment includes pressure calibrator and vacuum calibrator.

2.4 The environmental conditions are 15~25℃ and the relative humidity is not more than 85%. The ambient pressure is atmospheric pressure, and the pressure gauge should be allowed to stand for at least 2 hours before verification.

2.5 The working medium shall be a pressure gauge with a measuring upper limit not greater than 0.25MPA, and the working medium shall be clean air or non-toxic, harmless and chemically stable gas. The lower limit of measurement is not more than (0.25~250)MPA, and the working medium is non-corrosive liquid.

3. Verification of indication error, return error and tap displacement

3. 1 indication error verification method, the indication verification of pressure gauge should be carried out according to the scale line marked with numbers, and the pressure should be increased (or decreased) gradually and smoothly during verification. When the indication reaches the detection limit, the pressure source shall be cut off, and the pressure shall be maintained for 3MIN, and then the pressure shall be steadily reduced (or increased) in the reverse order of the original verification point.

3.2 Indication error. For each verification point, during the step-up (or step-down) and step-down (or step-up) verification, the difference between the front and rear instructions of the light box and the standard instructions shall meet the requirements of Table 1.

3.3 The return error refers to the absolute value of the allowable error specified in table 1 when verifying boost (or buck) and buck (or boost) within the same inspection time.

3.4 Tap the displacement. For each verification point, during the step-up (or step-down) and step-down (or step-up) verification, the change of the indicated value caused by the light case is not greater than 1/2 of the absolute value of the allowable error specified in the table1.

4. Verification method of vacuum pressure gauge

4. 1 When the upper limit of pressure measurement is (0.25~250)MPA, the vacuum part should be checked, and the pointer should point to the vacuum part when evacuating.

4.2 When the upper limit of pressure measurement is 0. 15MPA, the vacuum part shall be checked at two points.

4.3 When the upper limit of pressure measurement is 0.06MPA, the vacuum part shall be verified at three points. `

Table 1

accuracy grade

Basic error limit (percentage of range)

twelve?o'clock?at?night

measuring range

Over 90%

measuring range

The rest

With stop pin

Without stop pin