Owner manual

P/R60 & P/R65 Page 11
f) Measure the voltage between the red and green wires. The reading should be
between 160 and 240 mV; otherwise, the probe is defective. If the voltage is
OK proceed to the next step.
g) Rinse the probe and place it in 600 mV solution. Allow it to stabilize then check
the voltage again between the red and green wires. If the voltage is between
560 and 640 mV, the probe is within specifications.
5.2 Checking Probes P65 and R65 (4-20 mA output)
The operation of the 2-wire, 4-20 mA, probe can be checked by a few simple
measurements. Two pH buffer solutions, 7 pH and either 4 pH or 10 pH, and a dc
milliammeter are required.
5.2.1 P65C pH Probe
a) Disconnect the red wire at the instrument or power supply and connect it to the
milliammeter (-) black.
b) Connect the milliammeter (+) red to the instrument or power supply red wire
output terminal.
c) Rinse the probe and place it in 7 pH buffer. Allow the temperature of the buffer
and probe to stabilize at room temperature.
d) Check the offset of the probe by reading the milliammeter. The reading should
be between 11 and 13 mA. If not the probe is defective. If the offset is OK,
note the exact reading and proceed to the next step.
e) Rinse the probe and place it in 4 pH or 10 pH buffer. Allow the temperature of
the probe and buffer to stabilize at room temperature. Now check the span of
the probe by reading the milliammeter. If the probe is in 4 pH buffer, the
reading should be between 2.85 and 3.99 lower than the reading obtained in
(d).
If the probe is in 10 pH buffer, the reading should be between 2.85 and 3.99
higher than the reading obtained in (d).
If this test is not satisfied the probe is defective.
If you wish to check the temperature compensator proceed to step (f).
If the span of the probe drops below 2.85mA than the probe still can be used
adjustments will have to be made to the receiving device to compensate for the
low span.
f) To check the operation of the temperature sensor in the probe, heat the buffer
used in step (e) with the probe in it to about 50°C. The milliammeter reading
should be within ±0.15 mA of the reading observed in step (e).