1、 Overview of Automatic Calibration System for Thermocouples and Thermistors

The TX-WZJ-T-L thermocouple and thermal resistance automatic calibration system (hereinafter referred to as the device) is one of the latest fourth generation thermal automatic calibration products developed by our company. It is a new generation product developed entirely using the language of the Windows environment in the Windows environment. The system is centered around a high-end microcomputer, equipped with a high-precision imported digital multimeter, as well as a measurement and control system consisting of a low potential scanning switch, power regulator, and other components. The operator can easily operate the entire process with a mouse under the Chinese Win95/Win98/WinMe/XP operating system, and the microcomputer system displays real-time temperature control curves, temperatures, and calibration time parameters of the calibration furnace (or oil tank, etc.). The system fully processes data in accordance with the current national metrological verification regulations, and can print various record forms and verification certificates. It can also retain original records for future reference. The system has fully automated the calibration process of thermocouples and thermal resistors, including automatic temperature control, automatic calibration, automatic data processing, and automatic printing of calibration results. Greatly reducing the labor intensity of operators and improving the quality of calibration work. This device also provides authentication programs and data file management programs for the system, providing convenience for operators to archive, retrieve, and query the authentication and verification results of the system.

2、 Main performance characteristics of thermocouple and thermistor automatic calibration system

1. The advanced operating method uses Windows software programming and runs entirely on the Win95/Win98/WinMe/Win XP operating platforms. Fully in line with the operating habits of the Windows environment, the window interface, drop-down menu, and the use of a mouse to select input parameters and perform process operations are powerful, easy to use, flexible, and fast.

2. The highly automated calibration process includes continuous automatic temperature control, automatic calibration, automatic data processing, and automatic printing of various calibration records and certificates.

3. High precision and high resolution are selected using advanced six and a half bit high-precision imported numerical tables. Accuracy of 0.005% and resolution of 0.1uV; 0.1m Ω. During the detection process, further digital filtering and elimination of bad values are applied to the sampled data.

4. During the verification process, the monitor displays the temperature change curve of the verification furnace (or oil tank, etc.) in real time, as well as the temperature of the verification furnace (oil tank)

Verification point temperature, verification process, cold junction temperature, millivolt value of temperature control thermocouple (resistance value of temperature control thermistor), and verification time.

5. Fully functional and flexible configuration

● It can verify various grades of low-cost metal thermocouples and grade II precious metal thermocouples, as well as various grades of thermal resistors

Can verify two-wire (four wire) and three wire heating resistors

Multiple batches of calibration can be performed on the thermistor at the same temperature point; It can calibrate 0 ℃ and 100 ℃ points at different times, and the program automatically compiles and synthesizes reports, which is more in line with the actual situation of thermal resistance calibration and can effectively improve work efficiency

● It has multiple cold end compensation methods. Equipped with zero point, input room temperature, and automatic tracking compensation for cold end for operators to choose from

The compensation wire can be adjusted to make the calibration results more accurate

The temperature point can be set arbitrarily. Thermocouples operate between 300 ℃ and 1100 ℃, with intervals of 50 ℃; Hot spot resistance between 50 ℃ and 300 ℃: set arbitrarily every 10 ℃

Low temperature thermocouples (50 ℃~300 ℃) can be used to calibrate work in oil tanks

There are interface drivers with multiple number tables available, and operators can freely choose from the menu, increasing the flexibility of system configuration. Equipped with manual/automatic switching function, providing operation methods in special situations

6. High temperature control accuracy and short calibration time. Multiple optimized direct digital control algorithms are used, and multiple sets of temperature control parameters for different objects are provided for selection. Ensure that the temperature change rate during the verification process is less than 0.2 ℃/min for the verification furnace; The oil tank temperature is less than 0.04 ℃/min. Thermocouples generally have a calibration time of about 30 minutes per calibration point, while thermal resistors take about 60 minutes.

7. The standardization level is high, and the calibration process, data processing, calibration records, and calibration certificates of thermocouples and thermal resistors in the report specifications fully comply with the national metrological calibration regulations JJG-351-96; JJG-229-98; The requirements of JJG-141-2000 regulations and the 90 temperature scale promotion manual. Especially, the verification procedure for thermal resistors has been reorganized in accordance with the latest JJG 229-98 regulations issued by the country.

8. The system has a certification testing function and is equipped with a certification testing module for thermocouples and thermal resistance calibration devices. It can automatically verify the total uncertainty, repeatability error, and temperature field of the calibration furnace and oil tank for thermocouples and thermal resistance calibration devices, and compile and print certification reports. It brings great convenience to the operator for system standardization and system review.

9. The data management function system is equipped with data file management function, which can store, archive, retrieve and query calibration reports. The operator can access or print any calibration record report or calibration certificate at any time. The device processes the preview and printing of the report in the spreadsheet 'Excel~' under 'Office 97 (2000)'. Due to the powerful functionality and convenient and flexible operation methods of Excel, previewing and printing reports are more user-friendly.

10. The protection measures are complete and equipped with a system self-test program, which can perform self-test on digital meters, main control boxes, thyristor power regulators, dedicated interface cards, and wire connections. When there is a situation of overheating, thermocouple breakage, or thermocouple short circuit, the system will automatically turn off the thyristor actuator, cut off the heating current, and prompt an alarm.

11. The hardware design is reasonable, and the production process is advanced. All key components are made of imported components and undergo strict aging and inspection before leaving the factory. The thyristor power regulator can provide three power regulation outputs. Provide convenience for operators to switch between different temperature control objects.

3、 Main technical specifications of thermocouple and thermistor automatic calibration system

1. Scanning switch parasitic potential ≤ 0.4uV

2. Resolution

Maximum potential measurement resolution of 0.1uV

The highest resistance measurement resolution is 0.1m Ω

3. Accuracy

Uncertainty of potential measurement ≤ 0.01%

Resistance measurement uncertainty ≤ 0.01%

The uncertainty of thermocouple calibration is ≤ 1.2 ℃ (including the annual variation of 0.7 ℃ for second-class standard thermocouples)

The uncertainty of thermal resistance calibration is ≤ 0.05 ℃

4. Stability of constant temperature

During the thermocouple calibration process, the furnace temperature change after constant temperature is ≤ 0.2 ℃/min

The temperature change of the oil tank after constant temperature during the thermal resistance calibration process is ≤ 0.04 ℃/min

5. Cold end automatic compensation: When the cold end temperature is within the range of (20 ± 10) ℃, the compensation error is ≤ 0.2 ℃

6. Verification temperature: Thermocouple 300-1100 ℃

Thermal resistance 0-300 ℃ (including low-temperature thermocouples)

7. Verification quantity: 10 thermocouples can be verified simultaneously

Thermal resistors can be tested simultaneously for 1-10 units, and multiple batches of testing are allowed at the same temperature point.

8. One continuous calibration point: 6 thermocouples; 3 thermal resistors

9. Verification time: Thermocouple verification, with an average of about 30 minutes per hundred under normal conditions.

10. This verification system processes data in accordance with the current national metrological verification regulations.

11. Working environment: ambient temperature of 20 ± 3 ℃; Relative humidity ≤ 75%

12. Power supply: AC 220V ± 10% 50 ± 1HZ