UGH017/0500
Series 1 Portable Chillers, PLC Control
T
ROUBLESHOOTING
6-19
Ohm
meter
OHMS
+
-
Volt
meter
Current
meter
black
black
black
red
red
red
VOLTS
CURRENT
Power
supply
To
Controller
Problem
No reading
Reading too low
Reading too high
RF Interference
Possible cause
No power to board.
RTD wires shorted.
Improper range of trans-
mitter (too low).
Condensation on board.
RTD opened.
Improper range of trans-
mitter (too high).
Condensation on board.
Input power not clean.
Solution
Check voltage at power supply. Measure volts across the +
and - of the power wires. Voltage should be 8 - 35 VDC.
Disconnect RTD before testing sensor resistance. Check
RTD with ohmmeter. Should be close to 100 ohms.
Disconnect black lead (-) and place current meter in series.
Check RTD with current meter. Current should be 4 -20
mA.
Inspect for condensation. Dry with hot air.
RTD opened. Disconnect RTD before testing sensor resis-
tance. Check RTD with ohmmeter. Should be close to 100
ohms.
Disconnect black lead (-) and place current meter in series.
Check RTD with current meter. Current should be 4 -20
mA.
Inspect for condensation. Dry with hot air.
Use twisted wires or shielded cable. RF resistant power
supply. Use a shielded cable to connect the sensor.
Connect the shield to ground. Encase the board in a RF
shielded enclosure.
RTD
sensor
Temperature
transmitter board
Temperature
transmitter board
Temperature
transmitter board
RTD
RTD
+
+
-
C
HECKING THE
T
EMPERATURE
T
RANSMITTER AND
RTD
CONT
’
D
