Needle acidometer troubleshooting

The indicating part of the pointer pH meter is similar to that of other pointer-type indicating meters; most of the integrated circuits of the digital pH meter A/D conversion part are 7107, so indication of part failure can be analogized in the previously mentioned failures.

1. Improper indication Because the instrument is used for a long time in a relatively humid environment, first check whether the electrode plug is in good contact. If the contact is bad, replace or clean the rusty part of the plug so that the contact is good; secondly, can the output voltage of the electrode be measured (measured in millivolts of the digital multimeter)? If the output voltage is unstable, replace it. If the external inspection is good, turn on the meter and measure whether the voltage of the operation amplification part is stable. Is the amplified voltage (current) stable? If it is not stable, first check whether the power supply voltage is stable? If unstable, add a regulated power supply; if the power supply voltage is stable, check whether the rectified DC voltage is stable. If not, replace the filter capacitor; if it is stable, replace the amplifier.

2. The instrument has a millivolt gauge. When the acidity is measured, the full scale is displayed and there is an alarm sound. If the electrode is open, or if the electrode plug is not plugged in, the joint is welded or disconnected, replace the electrode or connect the electrode and instrument. .

3. The application solution is more accurate, and the acid solution error is large. First adjust the "positioning" with a neutral solution, and then adjust the "slope" with an acidic solution or an alkaline solution. Because the pH meter distribution method is to 7.00 for the neutral point, and 0.00 and 14.00 as the 7.00 center point side of the seven scale distribution range, 0.00 and 14.00 is 7.00 range, so in practice should be used 7.00 Debug "positioning", debug "slope" with 0.00 and 14.00, in order to get an accurate range. The manufacturer has special instructions according to the manufacturer's instructions.

If it cannot be adjusted, check if the adjustable potentiometer is open or variable? If open or variable, replace it; check if the internal coarse potentiometer is open or variable? If open circuit or variable value, it will be replaced; and adjust the potentiometer, return to normal, no other failure after the inspection, can be considered static drift amplifier, mostly due to the drift phenomenon of electronic components after a long time.

If the RC components are normal and still cannot be adjusted, check if the comparator circuit is symmetrical? If it is asymmetrical, then repair the dummy solder joint and replace the variable value or open circuit resistance; if it is also normal, the amplifier must be replaced.

4. The electrode output voltage is unstable 1) The electrode is aging.

2) The reference solution inside the electrode is turbid.

3) The electrode has not been cleaned.

4) Oxidation of the electrode wire.

5) Welds occur in the joints.