First, introduced the thermo-element, the thermo-element is in the temperature survey applies the most widespread temperature component, his main characteristic is measured kisses the scope widely, performance quite stable, simultaneously the structure is simple, the tendency responds, can far pass on the 4-20mA electrical signal, is advantageous for the automatic control and the common control. The thermo-element measured the warm principle is based on the pyroelectric effect. Connect the closed path two kind of different conductors or the semiconductor, when two contacts place temperatures are different, in the return route will produce 热电�? this kind of phenomenon will be called the pyroelectric effect, also will be called fills the Baker effect. In the closed path produces 热电势has two kind of electric potentials compositions; Thermoelectric force and contact electricity. The thermoelectric force is refers to the identical conductor the beginnings and ends the electric potential which different produce because of the temperature, the different conductor has the different electron density, therefore they produce the electric potential is not same, when the contact electricity is as the name suggests refers two kind of different conductors contacts, because their electron density is different therefore has the certain electron scattering, after they achieved the certain balance forms the electric potential, the contact electricity size is decided by two kind of different conductors material nature as well as their contact point temperature. At present on the international application thermo-element has a standard standard, on international stipulated the thermo-element divides into eight different minute, respectively is B, R, S, K, N, E, J and T, its survey temperature lowest observable below zero 270 degree Celsius, most Gao Keda 1,800 degree Celsius, B, R, S belongs to the platinum series the thermo-element, because the platinum belongs to the noble metal, therefore they are called several which the precious metal thermoelectricity is left over by chance to be called the inexpensive metal thermo-element. The thermo-element structure has two kinds, is ordinary and the armor. The general thermo-element generally by 热电�? the insulation tube, the splice case and the connecting box and so on partially is composed, but the armor thermo-element is the thermo-element silk, after the insulation material and the metal splice case three combinations assemblies, becomes one kind of solid assembly after the stretch processing. But the thermo-element electrical signal actually needs one kind of special wire to carry on the transmission, this kind of wire we are called compensate the wire. The different thermo-element differently needs to compensate the wire, its main function is with the thermo-element connection, causes the thermo-element the senate to be far away the power source compared to the end, thus causes the senate compared to the end temperature control. Compensates the wire to divide into compensating and the lengthening two kinds, lengthens the wire the chemical composition with the thermo-element which compensates same, but is actual, the lengthening wire also certainly is not with with the thermo-element same material quality metal, generally uses with the thermo-element has the same electron density the wire to replace. Compensated the wire with the thermo-element segment generally all is very bright, the thermo-element positive electrode connection compensated the wire the red streak, but the cathode connected the color which was left over. General majority of compensates the wire the material quality all to use the copper nickel alloy.
Next we introduce the thermal resistance, the thermal resistance although applies in the industry quite is also widespread, but because he measured the warm scope caused his application to receive the certain limit, the thermal resistance had measured the warm principle was based on the conductor or the semiconductor resistance value the characteristic which changed along with the temperature change. Its merit also very many, also may beyond conduct electricity the signal, the sensitivity high, stability strong, the interchangeability as well as the accuracy quite are all good, but needs the power source to drive, cannot the instantaneous measurement temperature change. The industrial used thermal resistance generally uses Pt100, Pt10, Cu50, the Cu100, platinum thermal resistance to measure the warm scope generally for below zero 200-800 degree Celsius, the copper thermal resistance for below zero 40 to 140 degree Celsius. Thermal resistance and thermo-element same discrimination type, but he actually does not need to compensate the wire, moreover the specific heat 点偶 is cheap. The article originates from:
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