The calibration environmental conditions and their requirements are as follows:
a) Ambient temperature: 20 °C ± 5 °C
b) Relative humidity: 30-60%
c) There are no measurable electric, magnetic, positive and negative ions around
d) Ground wire, ground wire resistance <100Ω
2, Calibration equipment
The equipment used for calibration shall be calibrated by the metrology technical organization to meet the calibration requirements and within the validity period.
Calibration equipment mainly includes: DC high voltage meter, DC high voltage power supply, standard flat electrode, distance adjuster and so on. The test chart is located on the center line of the calibration plate. The block diagram of the non-contact electrostatic voltmeter calibration device is as follows:
The equipment and equipment requirements are as follows:
C——calibrated product: static test table
D1——DC high voltage power supply: output range -30KV～+30KV, continuously adjustable, or minimum step 1V, the measurement uncertainty is less than 1/4 of the allowable error limit of the calibration table;
D2——DC high voltage meter: measuring range -40KV～+40KV, the measurement uncertainty is less than 1/4 of the allowable error limit of the calibration table;
D3——Standard plate electrode: The plate electrode should be round or square rounded. The radius of curvature of the edge of the electrode should not cause corona. It is recommended to wrap the edge of the electrode with insulating material; the area of the plate should be large enough. The diameter or side length should be no less than 0.4m. Our calibration plate size is 600mm*600mm square stainless steel plate.
——Protection resistance: The resistance of the resistor should be >20KV, the protection current and the current of the human body are <5mA, and the resistance value meets the requirements of the following formula:
Where: for protection of resistance, the unit is ohm (Ω);
The resistance of the insulating bracket is in ohms (Ω), the resistance is >1013Ω, and the compressive strength is >25KV.
The above two resistors, their different resistance values, may cause the detected static voltage values to be different under the same standard voltage.
S1 - insulated bracket
S2——scale, measuring range: 5mm～700mm, measurement uncertainty less than 0.5mm
S3——Distance adjuster: Place the test meter on the calibration device. The front end of the test chart should be extended. The geometry and material of the support should be minimized to affect the electric field distribution around the front end of the test chart.