Example of pH Meter Fault Analysis
1. During the use of the acidity meter instrument, it was found that the instrument cannot be zeroed when adjusting the zero adjustment potentiometer, but the number can be changed
Fault inspection and analysis: When the instrument is in normal condition, adjust the zero adjustment potentiometer, and the instrument can jump. Check the preamplifier, measure the integrated block of the preamplifier with the DC voltage of the multimeter, and find that the voltage cannot be adjusted, which indicates that the circuit is faulty here. match.
Troubleshooting: After replacement, the instrument is put into normal use.
2. The pH meter indicates no change
Fault inspection and analysis: There is no change in the indication of the instrument. It may be that the transmitter is faulty or the probe is polluted, resulting in the failure of normal measurement. Use the signal transmitter to simulate the probe to send a signal to the transmitter. The output of the transmitter changes, and the transmitter is normal. The pH analysis probe was disassembled and checked, and the probe was found to be contaminated.
Troubleshooting: After cleaning the probe, the meter is normal.
3. The pH meter indicates severe fluctuations
Fault inspection and analysis: The reason for the violent fluctuation of the instrument indication is the power supply fluctuation of the transmitter, the circuit fault or the connection line between the transmitter and the measuring probe. Use the signal transmitter to simulate the probe to send signals to the transmitter. The output changes normally, there is no problem with the transmitter, and the power supply is also stable. The problem lies in the connecting cable or line connection.
Troubleshooting: After replacing the connecting cable, the indicator indicates normal.
4. The glass pH electrode and circuit of the industrial pH meter are in good condition, and the measurement error is large after being put into operation, and even cannot work normally
Fault analysis: The analysis is caused by two reasons. One is that the shielded cable, junction box or terminal insulation resistance between the measurement pH electrode and the high-resistance converter is reduced. Because the internal resistance of the glass pH electrode is very high, if the terminal between the pH electrode and the converter is damp, the shielded cable is mildewed, and the potassium chloride solution used for the reference pH electrode pollutes the terminal box or penetrates into the cable cord. The oil or sewage on the belt remains on the terminal, or the terminal box is not sealed, and the dust accumulates in it, etc., which can cause the insulation to drop. The second is that there are large electromechanical equipment near the installation environment of the instrument, and the excessive current interferes with the indication value of the instrument.
Troubleshooting: handle accordingly.
5. When measuring with a pH meter, the measurement is not accurate
Fault inspection and analysis: The inspection found that the measured medium contains oil, because when the medium contains a large amount of oil and impurities, it will pollute the pH electrode.
