Thermal Calibration

The high-temperature system THERMOCAL from SCHWING is a versatile calibration and test system especially suitable for the area of final control of thermometers and thermal instruments as well as use in test labs. THERMOCAL is based on the SCHWING fluidized bed technology.

Technical basics

Air or inert gas is introduced from below, through a special diffusion plate, into a retort with fine-grain aluminum oxide, mixing intensively with the solids. This creates a fluidized bed in the measuring chamber (retort) where the Al2O3 solid particles move at low gas velocities without significant kinetic energy. The fluidized bed in the retort conducts heat extremely well and because of its mass possesses an enormous heat capacity. Test specimens such as thermocouples or other sensors can be immersed without problems.

The calibration and test system THERMOCAL is heated indirectly via electric heaters and can be used over a large temperature range from 50 °C to 1100 °C with top precision. The precise calibration process of THERMOCAL, which can be reproduced at any time, is handled by an electronic controller with NiCrNi thermocouples and direct measured value indication.

Many times an oil bath, which soils the temperature measuring instruments, is used for conventional calibration. The Al2O3 powder used for the THERMOCAL calibration bath, by contrast, is odorless, non-toxic, non-flammable, neither corrosive nor aggressive and particularly clean in handling and above all, it does not leave any oil or salt residues on the test specimen.

Applications and markets

Calibration via an oil bath is not a solution for many industries since oil would soil the test specimen or affect it too strongly. In addition, this approach requires more time because of the subsequent cleaning required.

A wide variety of temperature measuring instruments, temperature probes and temperature sensors are calibrated economically and cleanly with the systems from SCHWING. In addition to the special cleanliness, SCHWING Technology’s added benefit is its extreme accuracy. This is especially important when production-related material damage can be expected as a result of even minor temperature deviations.

Such temperature measuring instruments, used, for example, in CHP units, in the thermo-chemical industry and in the area of gas blast furnaces, must be absolutely reliable and precise. SCHWING ensures highest level calibration results which are documented according to the requirements and standards.

Systems and solutions

The thermal calibration system THERMOCAL from SCHWING Technologies calibrates and tests thermal switches and other sensors from 50 °C to 1000 °C with the highest precision:

  • Top accuracy over a large temperature range
  • Clean handling of the test specimens without oil or salt residues

Temperature calibration and test bath: THERMOCAL TH 050

Calibration and adjustment of temperature probes and thermal instruments are tasks requiring precision. Achieving the required accuracy requires measuring and testing devices that ensure high temperature uniformity over the entire working range. The waste gas-free fluidized bed calibration bath THERMOCAL TH 050 is superbly suited for this requirement. It works in a temperature range above room temperature up to 600 °C at a bath constancy with only minimal fluctuations of +/- 0.15 °C for short-term and +/- 0.3 °C for long-term applications. The useful retort volume is a good 5.3 liters (diameter 150 mm, depth 305 mm).

The THERMOCAL retort, a cylindrical container from stainless steel, as well as all required measuring and control devices are accommodated by a single compact housing. The retort is completed by a diffusion plate through which the compressed air is finely distributed. In addition, it is equipped with a dual jacket through which the fluidization air is routed and heated. The temperature measurement device is located in the lower area of the retort.

The devices are equipped with two separate heaters as standard. The external heater, consisting of two heating bands, allows quick heating according to the position of the pertaining selector switch. It also serves as back-up heater at bath temperatures above 350 °C. The control heater, designed as a tubular heating element, is located directly inside the retort. The temperature is controlled via an electronic controller with NiCrNi thermocouples with analog or digital setting as well as a deviation or direct indicator.

Quality calibration: THERMOCAL TH 500-12

At a retort volume of 36 liters (diameter 300 mm, depth 510 mm) the waste gas-free and environmentally friendly system THERMOCAL TH 500-12 offers approximately seven times the capacity of the TH 050 and is therefore suitable for the calibration of larger thermocouples.

Beyond the presented benefits of the THERMOCAL TH 050 the fluidized bed calibration bath THERMOCAL TH 500[1]works in temperature ranges up to 1000 °C. It achieves a bath constancy of +/- 1.0 °C as well as a short-term stability of +/- 0.9.

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Wednesday, 12. August 2020