The main purpose of thermal calibrators is to verify the technical performance of voltage and current transformers used in the field or in the laboratory. In order to achieve this purpose, thermal calibrator and related equipment form a complete set of transformer calibration device. Since the performance indicators of thermal calibrators have a close technical relationship with related equipment, in order to correctly study and understand the overall concept of thermal calibrators, it is necessary to have a basic understanding of thermal calibrators.

Thermal calibrators in my country can be roughly divided into three generations: the first generation of electrical calibrators, which is cumbersome to operate and complicated in wiring; the second generation of calibrators uses more advanced electronic circuits, which are more convenient to use than the previous generation of calibrators, but need to be used in the measurement process. Manually switch gears, and less information is displayed during the test. Most of the third-generation calibrators use single-chip microcomputers, which improves the intelligence of the instrument. Some instruments have a computer communication interface, which improves the level of office automation.

Here are the main features of the third-generation thermal calibrator:

(1) The single-chip microcomputer is used to realize the measurement, control and display functions;

(2) With computer interface, improve the level of office automation and reduce labor intensity;

(3) Large screen display, friendly operation interface, rich measurement information;

(4) It can automatically measure the transformer and automatically switch the current and voltage load boxes;

(5) There are good capture measures, and users can be notified of error information in a timely manner;

The instrument can reach level 2. At present, most calibrators on the market use the RC phase-shift 90° method to achieve data measurement. This method is susceptible to ambient temperature and power frequency. Once the above environment changes, its measurement data will be greatly affected.

The thermal calibrator uses a unique circuit principle and DSP technology to avoid the above problems.

From the measurement principle, thermal calibrators can be divided into direct comparison type and differential measurement type.

The early transformer calibrators were mainly designed on the principle of direct comparison, that is, the secondary voltage or current of the standard transformer and the tested transformer were sent to the transformer calibrator respectively. Measurement circuits such as voltage dividers, magneto-potential comparators measure the differential voltage or differential current between the two, which is the ratio difference and phase difference of a proven voltage transformer or current transformer with respect to a standard transformer.

Precautions:

1. When calibrating, the connection position of the contact socket of the thermal calibrator should be correctly selected to avoid connecting to the normally open or normally closed contacts of the density relay.

2. If the test result of this operation does not meet the factory value, the test should be rechecked. If it is confirmed to be unqualified, it should be handled by the user of sulfur hexafluoride electrical equipment as required.

3. The pressure and temperature indication of the thermal calibrator platform used should be verified by the metrological verification department. The verification period shall be handled according to the national pressure and thermometer verification period.