Sel 2414 - Thermocouple Inputs; Thermocouple Calibration

2.18
SEL-2414 Transformer Monitor Instruction Manual Date Code 20130214
Installation
Rear-Panel Connections
Thermocouple Inputs
The device supports as many as ten J, K, T, or E type thermocouple inputs with a
measurement range of -50°C to 250°C. Inputs are divided into two isolated banks
of five channels each. See Specifications on page 1.7 for type test performance
and compliance.
Each channel provides a plus and minus terminal that will accept wire as large as
18AWG. Thermocouples should be installed according to standardized and
accepted practices. All thermocouple cables should be shielded to increase
immunity to EMI. Terminate the thermocouple shield in the COMP/SHLD termi-
nal.
Each thermocouple input reading is based on a moving 30-sample average. You
can turn off the 30-sample average in the device with the ESAMPAVG setting.
Be sure to connect wiring to the thermocouple inputs with the correct polarity.
Refer to Figure 2.13 for a proper installation example.
Thermocouple Calibration
Although the thermocouple inputs have been factory calibrated specific to the
SEL-2414 system ordered by the user, it is recommended that the user calibrate
the installed system to achieve highest thermocouple accuracy.
In-Field System Calibration Procedure
Step 1. Power-on the unit and let soak for 60 minutes.
Step 2. Connect the installed thermocouples to the unit.
Step 3. Set the channel for the respective type (J, K, T or E).
Step 4. Ensure all channel gain settings are set to 1.0.
Step 5. Ensure all channel offset settings are set to 0.
Step 6. At the maximum possible application temperature, measure the
temperature of the thermocouple junction at the far or “hot” end
with an independent calibrated temperature measurement unit.
Record this as “Set_high”. Record the measurement taken by the
unit as “Actual_high”.
Step 7. Repeat the step above, but at the minimum possible application
temperature. Record the data as “Set_low” and “Actual_low”.
Step 8. Calculate gain setting: gain = (Set_high - Set_low) / (Actual_high
– Actual_low)
Step 9. Calculate offset setting: offset = Set_high – (Actual_low*gain)
Figure 2.12 Analog Input and Analog Output
01
02
AI_01
01
02
AO_01
Figure 2.13 RTD Card and Universal Temperature Card 3-Wire RTD Wiring
01
02
03
θ
TC1
+
−
COMP/SHLD