If the mechanical and electrical is AC24V, in the mechanical and electrical bias line to ground a 470K pressure sensitive resistance; if the mechanical and electrical is AC220V, then add 471K pressure sensitive resistance. If the meaning is heavy, if the peak and low voltage of the mechanical and electrical commutation.

The measurement of the pressure sensitive resistance: the same as the voltage sensitive parallel in the circuit, when the resistance of the two sides of the voltage to produce a sharp change, the resistance of the current fuse fuse, play a role in the protection of. The voltage sensitive resistor is used in the circuit, which is often used in the power supply overvoltage protection and voltage regulation. When measuring the multimeter 10K file, pen connected to two multimeter on the resistance, should show marked on the varistor resistance, if beyond this value, then clarify the varistor has been damaged. Nominal parameters of the pressure sensitive resistance:
Varistor with the letter "MY", such as J for home, behind the letters W, G, P, L, H, Z, B, C, N, K for the separation voltage regulation, overvoltage protection, high frequency circuit, lightning protection, arcing, denoising, compensation, degaussing, high or high reliability etc. hand. Although the pressure sensitive resistance is able to receive a great surge of electrical energy, but not to be able to sustain a continuous current of more than Ma, it is necessary to consider this point when used as an overvoltage protection. The selection of the pressure sensitive resistance, the same as the normal choice of nominal voltage sensitive voltage V1mA and the flow capacity of two parameters.
1, the so-called pressure sensitive voltage, that is, the breakdown voltage or threshold voltage. The current value of the voltage in the designated, conducting voltage when the varistor measured by 1mA DC current in most cases, the size of its products to the breakdown voltage range from 109000V. According to the detailed needs of accurate selection. As usual, V1mA=1.5Vp=2.2VAC, Vp is the peak value of the additional voltage of the circuit. VAC useful value for extra switching voltage. ZnO pressure sensitive resistance is very important for the choice of voltage, it is related to the protection of the consequences and the use of life. As a supply voltage for electrical appliances with additional 220V, while varistor voltage value V1mA=1.5Vp=1.5 * 1.414 * 220V=476V, V1mA=2.2VAC=2.2 * 220V=484V, is based on the breakdown voltage of the varistor in between 470480V optional.
2, the current capacity, the maximum pulse current peak is a temperature of 25 DEG C under the condition of current times against delimit blow blow current waveform and defined, the varistor voltage change is not across the maximum pulse current value of + 10%. In order to extend the service life of the device, the amplitude of surge current received by the ZnO pressure sensitive resistor should be less than the maximum flow rate of the product given in the manual. However, from the cover of the consequences of the choice of the flow of the choice of a large number of good. In many cases, flow through reality generation is difficult to accurately calculate the product selection of the 220KA. Such as hand products flow can not meet the request, the varistor parallel a few single use, stable parallel varistor, the flow rate for each single varistor and the numerical. The voltage characteristics of the parallel connection of the request are similar, and the shunt is not uniform and the destruction of the pressure sensitive resistance is easily caused.

The use principle of the pressure sensitive resistor:
The voltage sensitive resistor is a kind of element which has the function of transient voltage restraint. It can be used to replace the combination of transient restraint diode, Qi Na diode and capacitor. The voltage sensitive resistor can stop the protection of the circuit of IC and other equipment, and avoid the damage caused by electrostatic discharge, surge and other transient current (such as lightning strike, etc.). Use only when the varistor is connected to the protected equipment or IC circuit, when the voltage is higher than a certain value Shashi, varistor resistance reduce quickly, conduction current, so as to cover IC or electrical equipment; when the voltage is lower than the voltage varistor that value, varistor resistance is extremely high, almost open it will not affect the device or electrical equipment in things.