Emerson 54ea Pet Fence User Manual


 
104
MODEL 54eA SECTION 15.0
TROUBLESHOOTING
15.15 MEASURING REFERENCE VOLTAGE
Some processes contain substances that poison or shift
the potential of the reference electrode. Sulfide is a good
example. Prolonged exposure to sulfide converts the ref-
erence electrode from a silver/silver chloride electrode to
a silver/silver sulfide electrode. The change in reference
voltage is several hundred millivolts. A good way to check
for poisoning is to compare the voltage of the reference
electrode with a silver/silver chloride electrode known to
be good. The reference electrode from a new sensor is
best. See Figure 15-6. If the reference electrode is good,
the voltage difference should be no more than about 20
mV. A poisoned reference electrode usually requires
replacement.
FIGURE 15-6. Checking for a Poisoned
Reference Electrode.
Refer to the sensor wiring diagram to identify the
reference leads. A laboratory silver/silver chloride
electrode can be used in place of the second sensor.