Determining The Error From The Current Situation For Temperature Measurement Errors - Omron EJ1 User Manual

Determining the Error from the Current Situation for Temperature Measurement Errors

7-5 Determining the Error from the Current Situation for
Temperature Measurement Errors
Error in Measured Temperature or Temperature Cannot Be Measured
Connection The thermometer polarity or connected terminals are wrong. • Rewire correctly.
A thermometer that cannot be used with the EJ1 has been
connected.
The thermometer has burnt out, short-circuited, or deterio-
rated.
No thermometer is connected.
A compensating conductor applicable to the thermocouple
has not been used.
A device using metal other than a thermocouple or compen-
sating conductor has been connected between the thermo-
couple and EJ1 terminals.
The connection terminal screws are loose and the connec-
tion is imperfect.
The thermocouple lead or compensating conductor is too
long and is affected by the conductor resistance.
The resistance of the 3 conductors between the thermome-
ter and the EJ1 terminals is different.
Installation Affected by noise emitted by devices near the EJ1.
The thermometer lead is too close to the power line and is
receiving induction noise from the power line.
The thermal response is slow because the installation posi-
tion of the thermometer is too far from the control point.
The ambient temperature of the EJ1 exceeds the rating.
A wireless device is used in the vicinity of the EJ1.
The terminal block temperature is inconsistent due to heat
radiated from peripheral devices.
An air current or draft is striking the EJ1 terminal block.
Settings The input type settings are incorrect.
The temperature unit settings are incorrect.
The measured temperature seems incorrect due to the input
compensation setting.
Procedure The input terminals for a thermocouple input are shorted.
The thermometer was changed or the switch settings
changed while power was ON.
Easy Method for Checking Thermometers
Platinum resistance thermometers: 1. Connect a 100 Ω resistor between thermometer input terminals A and B
Thermocouples:
Possible cause
and short B and B.
2. The EJ1 is working if the measured temperature is 0.0 ° C or 32.0 ° F.
1. Short the thermometer input terminals.
2. The EJ1 is working normally if the temperature in the vicinity of the ter-
minal block is measured.
Countermeasure
• Change to a compatible thermometer.
• Replace with a better quality thermometer.
• Connect a thermometer.
• Directly connect a thermocouple with a long lead.
• Use an applicable compensating conductor.
• Connect a device specifically for thermocouples.
• Tighten the screws securely.
• Use a thicker compensating conductor.
• Change the wiring location and shorten the wires.
• Use conductors with the same resistance for all three ter-
minals, A, B, and B terminals.
• Move the EJ1 away from devices emitting noise.
• Connect a surge suppressor or noise filter to devices emit-
ting noise.
• Separate the thermometer lead from the power line.
• Run the thermometer lead through a different pipe or duct
from the power line.
• Do not wire the thermometer lead and the power line in
parallel.
• Wire a shorter thermometer lead.
• Use a shield on the thermometer lead.
• Install the thermometer with the end of the protective tube
closer to the control point.
• Keep the ambient temperature between the rating range of
− 10 to 55 ° C.
• Shield the EJ1.
• Move the EJ1 to a position where it will not be exposed to
heat.
• Do not let air currents or drafts strike the terminal block.
• Correct the input type settings.
• Correct the temperature unit settings.
• Set the input compensation to 0.0.
• Connect a thermocouple.
• Cycle the power.
Section 7-5
181