Section 1 Environmental Equipment Conditions

1. environmental conditions

(1) Ambient temperature: 22±3℃;

(2) Relative humidity: 20% ~ 75%;

(3) Before calibration, the temperature of the parts to be calibrated and the standard parts should be equilibrated for about 2 hours; the parts to be calibrated and the standard source should be powered on and preheated for more than half an hour.

2. Calibration equipment

(1) Standard instrument: standard source

Section 2 Calibration items and calibration methods

1. Appearance inspection

The instrument should be marked with the instrument name, manufacturer name (or trademark), factory serial number, CMC mark and other information to ensure its correct use, general signs and symbols, and should not have defects that can cause measurement errors and affect accuracy.

2. Calibration of ammeter

First adjust the zero position of the meter to be calibrated, and then connect to the measurement loop. Adjust the current source and slowly increase the current so that the indicator of the meter to be calibrated sequentially indicates each digital graduation line, and record the actual values of these points.

Increase the current to above the upper limit of the range, and immediately and slowly decrease the current so that the indicator points sequentially on each numbered graduation line, and record the actual values at these points.

The basic range is calibrated to 3 to 5 points (with digital graduation points), and other ranges are calibrated to 1 to 2 points.

3. Calibration of voltmeter

First adjust the zero position of the meter to be calibrated, and then connect to the measurement loop. Adjust the voltage source and slowly increase the voltage so that the indicator of the voltmeter under test sequentially indicates each digital scale, and record the actual values at these points.

Increase the voltage above the upper limit of the range, then slowly decrease it immediately so that the indicator points sequentially on each digital graduation line, and record the actual values at these points.

The basic range is calibrated to 3 to 5 points (with digital graduation points), and other ranges are calibrated to 1 to 2 points.

4. Calibration of power meter

Adjust the zero position of the meter being calibrated, and then connect it to the measurement loop. Adjust the voltage according to the indication of the monitoring voltmeter to make it equal to the rated voltage of the power meter being calibrated. After setting the power factor, slowly increase the current so that the meter being tested is indicated on each graduated line with numbers, and record the reading of the digital meter to calculate the actual value of the meter being calibrated.

Then increase the current to above the upper limit of the measuring range, and then slowly decrease it immediately, so that the indicator of the meter under test sequentially indicates on each graduation line with numbers, and record the actual values of these points.

The basic range is calibrated to 3 to 5 points (with digital graduation points), and other ranges are calibrated to 1 to 2 points.

5. Calibration of resistance meter

Use a standard resistance box to calibrate the resistance meter. When the minimum range of the resistance meter is R×1 (Ω), R×10 (Ω) is generally taken as the full calibration range, and the remaining ranges are non-full calibration ranges. The entire school measuring range should be calibrated at points with digital graduation lines within the measuring range. For non-full calibration ranges, only the median resistance with digital graduation lines is calibrated.

Short-circuit the test leads and adjust the zero position. Adjust the standard resistance box so that the indicator points sequentially on the calibrated graduation line, and record the actual value X0. The basic error of each selected graduation line is calculated according to formula (1).

λ=(X－X0)/XN (1)

 In the formula: X——the indicated value of the instrument;

 X0 - the actual value being measured;

 XN - Reference value.

 When the reference value of the resistance meter is the arc length of the effective range of the scale:

(1) Record the arc length BSL of the effective range of the scale, and short-circuit the test leads to zero.

(2) Sequentially adjust the resistance value of the adjustable standard resistance box (or active resistor) to the resistance corresponding to the digital graduation line, and record the arc length ΔBX of the indicator deviating from the digital graduation line. If the indicator is on the graduation line On the left, ΔBX is positive, on the right it is negative.

(3) Express the basic error as a percentage of the arc length. Calculate according to the following formula:

δ=ΔBX/BSL×100%

 Calculation formula of scale length BSL:

 BSL=Φ/180×Rθ

 In the formula: Φ——pi;

 R——radius of scale arc, mm;

θ——The radian of the working part of the scale, that is, the rotation angle of the indicator, degrees.