High speed pyrometers generally refer to thermometers used to measure temperatures above 500°C. Commonly used pyrometers include optical pyrometers, colorimetric pyrometers and radiation pyrometers. In addition, thermocouple thermometers can also be used to measure high temperatures below 3000°C. However, because the measuring range of a thermocouple thermometer can be as low as -200℃, it is generally not classified as a pyrometer.

The photoelectric high speed pyrometer uses photoelectric devices as the sensitive components of the instrument, instead of human eyes to sense the brightness changes of radiation, and convert this brightness information into an electrical signal proportional to the brightness. This signal is amplified and measured, and its magnitude corresponds to the temperature of the measured object. In order to reduce the influence of changes in the performance parameters of photoelectric devices and voltage fluctuations on the measurement results, photoelectric high speed pyrometers work on the principle of negative feedback.

The radiant energy emitted from the surface of the object to be measured is focused by the objective lens, passes through the aperture in the diaphragm and the light shield, passes through the red filter installed in the light shield, and is incident on the optoelectronic device (silicon photovoltaic cell). The light beam emitted by the measured object must cover the hole, which can be observed with the aiming system. The aiming system consists of a lens, a mirror and an observation hole.

The radiant energy emitted by the feedback lamp from the high speed pyrometer passes through the holes in the light plate, and is also projected onto the same optoelectronic device through the same red filter. A light modulator is placed in front of the light shield. The operating principle of the light modulator, the excitation coil passes through 50Hz alternating current, the resulting alternating magnetic field interacts with the permanent magnet, causing the modulator to vibrate 50 times per second, alternately opening and covering the hole, so that two beams of radiation Can be alternately projected onto the optoelectronic device, so the output end of the optoelectronic device generates a pulsed photocurrent corresponding to two beams of radiant energy and a frequency of 50 Hz. This pulsed photocurrent is amplified by the preamplifier and then sent to the main amplifier for further amplification. The DC current output by the main amplifier passes through the feedback lamp to control the brightness of the feedback lamp. When the brightness of the feedback lamp is equal to that of the measured object, the pulsed photocurrent is close to zero. At this time, the current through the feedback lamp represents the temperature of the measured object. An electronic potentiometer with temperature scale is selected to automatically indicate and record the magnitude of the current through the feedback. It can be seen from the above working principle that the brightness of the feedback lamp is close to the brightness of the measured object in the steady state.

Features of photoelectric high speed pyrometer:

1. The photoelectric pyrometer can automatically measure the temperature, which is easy to use and can avoid the subjective error of the operator.

2. High speed pyrometers have high sensitivity and accuracy.

3. Readings can be automatically recorded and remotely transmitted, which is conducive to centralized control of parameters.

4. The photoelectric device in the photoelectric high speed pyrometer can accept both visible light and infrared light. This makes the measurement range of the pyrometer not limited by the spectral sensitivity of the human eye and can develop towards low temperatures.

5.The high speed pyrometer responds quickly. However, due to the large dispersion of the feedback lamp and the optoelectronic device, the component interchangeability is poor. When the feedback lamp or optoelectronic device is replaced, the entire meter must be re-adjusted and scaled. This is the photoelectric high speed pyrometer in use. A problem that should be paid special attention to.