Digital display controller troubleshooting method

First, determine the fault within the temperature meter or meter outside the digital display controller external wiring power supply, input signal and output signal, so when the display shows an abnormal phenomenon, you should first use a multimeter to test the rear terminal signal, should Within the required value of the meter. For example, when the meter power is not displayed, first check whether the power supply of the meter is abnormal. If it is normal and the meter is still not displayed, it can be concluded that the power supply or related components of the meter is damaged; when there is an overflow or a jump, it can be measured. Whether the input signal has an open circuit or bad contact phenomenon. If an open circuit is detected, the fault occurs outside of the table. The open circuit of the signal can be found and can be normal after being eliminated. When the measured temperature is lower than the given value and the loop current meter is still zero , Can use the multimeter to measure the output signal of the rear terminal of the meter, normally it should be 10mA. If not, it means that the meter itself has problems. If there is, and the loop current still has no indication, it can be concluded that the fault occurs outside the meter, that is, the supporting ZK -1 There is a problem with the thyristor voltage regulator or ammeter that can be further searched and judged. By checking the signal on the terminal at the rear of the meter, it can be determined whether the fault is inside or outside the meter. When it is confirmed that the fault occurs within the meter, the fault can be further judged based on the fault phenomenon. The digital display of the fault is eliminated in the specific part of the meter.

Second, the fault causes the following digital display controller troubleshooting 1. Symptoms - display digital instability (hops)

1) bad instrument grounding;

2) The power supply is unstable;

3) Power transformer shield open circuit;

4) The internal reference voltage and negative power supply have a fault;

5) Potentiometer bad contact;

6) 7107 damage;

7) The power supply filtering regulator is not good;

8) The room temperature compensation circuit and the reference power supply have bad foundations;

9) Automatic zero circuit damage;

10) Welds or connectors in the contacts, connectors, or components in the watch;

11) The noise in the integrated op amp is too high.

2. Failure phenomenon - output is 0mA

1) Output transistor damage;

2) The integrated op amp output is negative potential;

3) The bridge power supply is damaged or its circuit connection is open;

4) Output transistor emitter resistance or lead open circuit;

5) The output connection is open.

3. Failure phenomenon - the output is 10mA

1) Output transistor breakdown;

2) The integrated op amp output has a positive potential to turn on the transistor;

3) Damaged integrated amplifier.

4. Symptoms - output instability Digital display controller troubleshooting 1) excessive external interference;

2) The bridge power supply is unstable;

3) Welds on the device or solder joint;

4) poor connector contact;

5) The internal noise of the integrated op amp increases;

6) The power supply voltage is too low;

7) Output transistor characteristics are not good.

5. Symptoms - the monitor is not lit 1) The power transformer is damaged or the connection is open;

2) Fuse blown (open circuit);

3) Digital panel meter power connection open circuit;

4) The LED display is damaged.

6. Failure phenomenon - display overflow 1) The input signal line is open in the table part;

2) Damage to the amplifier power supply;

3) Integrated op amp damage;

4) 7107 damage;

5) The digital panel input is open.

7. Failure phenomenon - only display "000

1) Signal conversion part of the bridge power supply is damaged;

2) Damage to the amplifier power supply;

3) 7107 damage;

4) Damaged integrated amplifier.

8. Failure phenomenon - Incomplete display 1) The LED display is damaged;

2) 7107 damage;

3) There is an open connection between the LED and 7107.

Troubleshooting method: When the above causes are determined, the damaged components are repaired. If they cannot be repaired, they can be replaced. Finally, Instrument World World Network reminds you that when the digital display controller used on the device is malfunctioning (damaged), the instrument maintenance personnel should not blindly repair it. According to the symptoms of the instrument, the approximate location of the fault should be determined first, and then targeted. Test and maintenance are also one of the ways to increase the efficiency of temperature meters.