Thermocouple temperature transmitter requires that the output voltage signal of the transmitter be in a linear relationship with the temperature signal input by the corresponding transmitter. However, the output millivolt value of a general thermocouple is nonlinear with the temperature it represents. The nonlinearity of various thermocouples is also different, and the degree of nonlinearity of the same thermocouple in different measurement ranges is also different. the same. For example, the characteristic curve of platinum-rhodium-pin thermocouple is concave upward, while the characteristic curve of nickel-chromium-nickel-aluminum thermocouple is concave upward at first, and becomes concave downward and presents an S shape when the temperature rises.
The thermocouple is non-linear, and the temperature transmitter amplifier circuit is linear. If the thermoelectric potential of the thermocouple is directly connected to the transmitter amplifier circuit, the temperature T is the same as the output voltage U of the transmitter. The relationship is non-linear. So in order to make the input temperature T and output voltage U of the temperature transmitter. Keep the linear relationship, the amplifier loop characteristics of the transmitter cannot be linear. Assuming that the characteristic of the thermocouple is concave upward, if you want to make T and U. The relationship is linear, so the characteristic curve of the transmitter amplifier circuit must be concave downward.
Main features of thermocouple temperature transmitter
Simple structure: There are no movable or elastic elements, so the reliability is extremely high and the maintenance is minimal.
Easy to install: the built-in structure especially shows this feature, without any special tools.
Convenient adjustment: The two potentiometers of zero position and range can perform zero migration or range change arbitrarily within the effective range of temperature detection, and the two adjustments do not affect each other.
Wide range of uses; suitable for liquid level measurement of high temperature, high pressure, strong corrosion and other media.