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