1. Turn on the power of the detection device, the light on the switch is off, there is no indication of the upper and lower temperatures, and the fuse is broken. Replace the fuse.

2. Start-up In the carbon and sulfur data frame, the carbon pool value and sulfur pool value will not change. Generally speaking, such failures are caused by no serial data. The check methods are as follows:

(1) Turn off all power supplies, and repeat the operation several times in accordance with "Operation steps from turning on to normal operation", the signal data is still not displayed on the screen.

(2) Turn off the power and check whether the serial connection plug is loose. Unplug the cable and plug it in again. No data continues to be transmitted after turning on the power.

(3) Use an extended circuit board to lead out the main board in the control box, use a multimeter to measure whether the main board's 5V power supply is normal, if not, check the power board. It is judged that the 89C51, GAL, and 232 chips on the motherboard may be damaged.

(4) The above inspections are all normal. Turn on the power and observe the data in the carbon data box on the screen. It means that the A/D7135 chip and its peripheral circuits corresponding to the carbon pool are good. On the contrary, there may be a problem with the components on the sampling board or the 8155 chip on the main board, the ±5V power supply for A/D is not good, and the printed circuit board is inserted reversely.

(5) In the above inspection process, if it is judged that the chips or the power supply have problems, the solution is to replace the chip or replace the corresponding printed circuit board.

3. There is serial data transmission, but the carbon pool or sulfur display signal value is abnormal. The inspection method is as follows:

(1) If the data is 2V or greater, there must be a problem with the 7135 chip or its peripheral circuit on the corresponding A/D sampling board.

(2) If the data on the upper screen jumps randomly, you must use a digital multimeter to test at the same time. If the numbers on the multimeter are normal, it means there is a problem with the device on the sampling board. If the measurement data of the multimeter is also abnormal, there may be a problem with the corresponding front plate.

(3) If the displayed data is very small and below 0.05V, there may be a problem with the light source or modulation motor in the corresponding measuring cell. At this time, you can first observe whether the voltages of the two in the F2 function are normal. To check whether the motor is normal or not, you can judge whether there is a slight vibration by pressing and holding the motor.