Temperature test circuit

Test - lowercase jpg

Kaixin micro test

Test probe P100-M3

As shown in the figure is a multi-channel temperature test circuit. The test circuit is mainly composed of a monostable delay circuit composed of 555 as a core. When the button AN is pressed, IC1 (555) is set because the 2 pin is low, and the high level of the 3 pin output causes the relay J1 to pull in, and the thermocouple of the channel is turned on accordingly. At the same time, the light-emitting tube LED1 is lit. Capacitor C1 is charged by R1. When the voltage on C1 is charged to make the potential of pin 6 reach 2/3VDD, 555 is reset. The low level of the 3-pin output is coupled to the lower 0.01μF capacitor to make IC22 pin low. IC2 is asserted. The output level is turned on correspondingly to the second thermocouple, and the above process is repeated, which is triggered in sequence to realize multi-channel temperature test.
If the switch K1 is closed in the circuit, the loop detection can be performed, and the measurement time of each stage is td=1.1R1C1. While the measurement is being taken, the LED is illuminated for the detection indication. For the circuit diagram (a), when the power is turned on, several LEDs may flash at the same time. For this reason, an improved circuit as shown in (b) can be used. After accessing the R and C networks, when the power is turned on, since the voltage on C cannot be abrupt, the reset end (4 pins) of 555 (Ic) is in a forced reset state, and the 3 pin outputs a low level, which is charged with the capacitor C. During the operation, the potential of the 4 feet is gradually increased. When the potential of the 4 feet is raised to the high level, the Ic of each level is in the waiting timing state, thereby improving the accuracy of the circuit test. This circuit is used to switch the thermocouple of the corresponding channel when testing multiple temperatures.