Tempco tec-220, Instruction Manual, Page: 26 / 36

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Step 6.
Set up the equipment according to the diagram above for calibrating the
cold junction compensation. Note that a K type thermocouple must be
used.
The 525A calibrator is configured as K type thermocouple output with
internal compensation. Send a 0.00°C signal to the unit under calibration.
The unit under calibration is powered in a still-air room with temperature
25±3°C. Wait at least 20 minutes for warming up. Perform step 1 as stated
above, then press the scroll key until the display shows .
Press the scroll key for at least 5 seconds. The display will blink for a
moment until a new value is obtained. If the display didn't blink or if the
obtained value is equal to –5.00 or 40.00, then calibration failed.
• Perform step 7 to calibrate gain of cold junction compensation if
required.
Step 7.
Setup the equipment same as step 6. The unit under calibration is powered
in a still-air room with temperature 50 ±3°C. Wait at least 20 minutes for
warming up. The calibrator source is set at 0.00°C with internal compen-
sation mode.
Perform step as 1 stated above, then press the scroll key until the display
shows . Press the scroll key for at least 5 seconds. The display will
blink for a moment until a new value is obtained. If the display didn't blink
or if the obtained value is equal to –199.9 or 199.9, then calibration failed.
This setup is performed in a high-temperature chamber, therefore it is rec-
ommended to use a computer to perform the procedures.
• Input modification and recalibration procedures for a linear voltage or a
linear current input:
1. Remove R60(3.3K) and install two 1/4W resistors RA and RB on the
control board with the recommended values specified in the following
table.
Low temperature coefficient resistors should be used for RA and RB.
2. Perform step 1 and step 2 to calibrate the linear input zero.
3. Perform step 3 but send a span signal to the input terminals instead of
60mV. The span signal is 1V for 0~1V input, 5V for 0~5V or 1~5V
input, 10V for 0~10V input and 20mA for 0~20mA or 4~20mA input.
• Final step
Step 8.
Set the LOCK value to your desired function.
Manual Calibration Procedures,
continued…