Troubleshooting From Symptoms: Measurement Errors - Omron CJ Series Operation Manual

Troubleshooting
5-2-1

Troubleshooting from Symptoms: Measurement Errors

Incorrect Measurement or No Measurement
Step
Connection The temperature sensor is connected to the wrong
terminals or polarity is reversed.
The temperature sensor connected to the Temper-
ature Control Unit is not compatible with the Unit.
The temperature sensor wires are broken, short-
circuited, or damaged.
No temperature sensor is connected.
The compensating conductor being used is not
compatible with the thermocouple.
Some equipment is connected between the ther-
mocouple and Temperature Control Unit that uses
metal different than the metal in the compensating
conductor or thermocouple.
The terminal screws are loose so there is poor
contact between the wires and terminals.
The thermocouple's lead wires or the compensat-
ing conductors are too long, so the resistance in
the wires is affecting operation.
The conductors between the temperature sensor
and the Temperature Control Unit's terminals
have three different conductive resistances.
Installation Noise from electric equipment around the Temper-
ature Control Unit is affecting operation.
The temperature sensor's leads run close to
power lines, so noise is being induced from the
power lines.
The temperature sensor is installed too far from
the point being controlled, so the response to tem-
perature changes is delayed.
The ambient temperature where the Temperature
Control Unit is installed exceeds the Unit's ratings.
Wireless equipment is being used near the Tem-
perature Control Unit.
The temperature around the Temperature Control
Unit is not uniform because of heat-generating
equipment near the Unit.
There is a draft (breeze) on the Temperature Con-
trol Unit's terminal block.
Settings The Input Type setting is incorrect.
The Temperature Units setting is incorrect.
The measured temperature appears to be shifted
because of the Input Compensation Value setting.
The Data Format setting is incorrect.
The host's ladder program is incorrect.
Possible Cause Remedy
Wire temperature sensor correctly.
Replace the temperature sensor with one that is com-
patible with the Temperature Control Unit.
Replace the temperature sensor with a good one.
Connect a temperature sensor.
• Directly connect a thermocouple with long lead wires.
• Use a compensating conductor that is compatible
with the thermocouple.
The equipment used for connections must be made
specifically for use with thermocouples.
Tighten the terminal screws.
• Use thicker compensating conductors.
• Change the wiring location to reduce the length of the
wiring.
Use conductors with the same resistance for the A, B,
and B' terminals.
• Move the Temperature Control Unit away from the
equipment that is generating the noise.
• Install surge protectors or noise filters on the equip-
ment that is generating the noise.
• Separate the temperature sensor's leads from the
power lines.
• Run the temperature sensor's leads in a conduit or
duct separate from the one carrying the power lines.
• Do not run the temperature sensor's leads parallel to
the power lines.
• Reduce the length of the temperature sensor's leads.
• Use shielded wire for the temperature sensor's leads.
Install the temperature sensor in a protective tube
closer to the point being controlled.
Install the Temperature Control Unit in a location with an
ambient temperature between 0 and 55°C.
Shield the Temperature Control Unit.
Move the Temperature Control Unit to a location where
it won't be affected by heat-generating equipment.
Eliminate or block the draft.
Set the Input Type correctly.
Set the Temperature Units correctly.
Set the Input Compensation Value to 0.0.
Check the Data Format set on pin 2 of the DIP switch
and correct the ladder program if necessary.
Section 5-2
77