PART FOUR - SERVICE AND MAINTENANCE
SECTION 3 - TROUBLESHOOTING
PRO-series Model C3 Conductivity Transmitter
Rev. 0-201
64
S
ECTION
3
3.1 Ground Loops
Determining if
Ground Loop Exists
The transmitter may be affected by a “ground loop” problem
(two or more electrically grounded points at different poten-
tials).
Symptoms Indicating a Possible Ground Loop
•
Transmitter reading is offset from the actual value by a
consistent amount, or ....
•
Transmitter reading is frozen on one value, or ....
•
Transmitter reading is “off scale” (upscale or downscale).
Although the source of a ground loop is difficult to deter-
mine, there are several common causes.
Common Causes of a Ground Loop
•
Components, such as recorders or computers, are
connected to non-isolated analog outputs.
•
Not using shielded cabling or failure to properly connect
all cable shields.
•
Moisture or corrosion in a junction box.
The following simple test can help to determine if there is a
ground loop:
1. With the conductivity MEASURE screen displayed, put
the sensor in a non-conductive container (plastic or
glass) filled with solution of a known conductivity value.
Note the transmitter reading for this solution.
2. Connect one end of a wire to a known earth ground
such as a metal water pipe. Place the other end of this
wire into the reference solution next to the sensor.
3. Note the transmitter reading now and compare it with
the reading taken in step 1. If the reading changed, a
ground loop exists.
TROUBLESHOOTING
