Temperature sensor insertion depth control

The normal operation of the temperature sensor element is to meet its operating conditions, one of which is its operating current, because the temperature sensor has a resistance value, when the current flows through the temperature sensor element, there will be power loss, it will heat, so in order to To reduce the temperature error caused by the sensor's own heating, so to meet the normal working conditions of the sensor, to minimize its own heat. This is why the temperature sensor is used under constant, low current conditions. So, for example, the platinum thermal resistance's normal operating current is 5mA, but our recommended operating current is 1MA. The reason is to reduce the measurement error due to self-heating of the temperature sensor element. The current is constant and its output has a linear relationship between temperature and potential.

The insertion depth of the temperature sensor is also a problem that is easy to overlook. Some customers require a very short insertion depth but a relatively large diameter. This is unreasonable, especially in the case of high temperatures, which is not desirable. In theory, the temperature sensor is inserted. Depth can generally be determined according to actual needs. However, the minimum insertion depth should not be less than 8-10 times the diameter of the temperature sensor protection sleeve. In order to ensure stable performance of the temperature sensor.

For example, the location and insertion depth of the thermocouple can not reflect the true temperature of the furnace, in other words, the thermocouple should not be installed too close to the door and the heating place, the depth of insertion should be at least 8 to 10 times the diameter of the protection tube; The gap between the protective sleeve of the thermocouple and the wall is not filled with heat insulation material, so that the heat in the furnace overflows or the cold air invades. Therefore, the gap between the thermocouple protection tube and the wall hole of the thermocouple is blocked with heat insulating material such as fireproof mud or asbestos rope to avoid cold and heat. Convection of air affects the accuracy of temperature measurement; the thermocouple cold junction is too close to the furnace body to make the temperature exceed 100°C; thermocouples should be installed as far as possible to avoid strong magnetic fields and strong electric fields, so thermocouples and power cables should not be installed in the Within the same conduit to avoid introducing interference caused by errors; thermocouple can not be installed in the area where the measured medium rarely flows. When using a thermocouple to measure the temperature of the gas in the tube, the thermocouple must be installed against the flow velocity and fully in contact with the gas. .

Knowing the operating current and insertion depth of the temperature sensor is necessary for us to select and use the temperature sensor. If you ignore these two details, it is easy to cause unstable or even damaged temperature sensor performance.