ThermoWorks 9135-156 HART SCIENTIFIC 3-POINT IR CALIBRATOR - Manual (Page 22)

9 Calibration Procedure
The 9135 should be calibrated regularly to ensure accuracy. A one-year or less
calibration interval is recommended. Calibration should only be performed by a
qualified and authorized technician.
The calibration of the 9135 entails adjusting the calibration potentiometers in-
side the instrument until the temperature of the IR target is close to the
set-point temperature as observed with a calibrated standard RTD at each of the
three set-points. The following are required:
• Standard calibrated RTD or thermistor, 3.18 mm (0.125") diameter and at
least 100 mm (4") sheath length, and a readout device, total uncertainty
0.2°C or better
• Potentiometer adjustment tool
The calibration procedure is as follows:
1. Insert the standard RTD or thermistor fully into the test well of the 9135
through the test well access hole in the right panel.
2. Set the set-point to 50°C and let it stabilize. Wait for the green ready LED to
light.
3. Adjust the potentiometer on the right one-half turn at a time, waiting one to
two minutes between adjustments, until the standard RTD or thermistor shows
the temperature is close to 50°C within 0.2°C. Adjust the potentiometer clock-
wise to increase the temperature or counter-clockwise to decrease the
temperature.
4. Set the set-point to 150°C and let it stabilize. Wait for the green ready LED
to light.
5. Adjust the potentiometer on the left one-half turn at a time, waiting one to
two minutes between adjustments, until the standard RTD or thermistor shows
the temperature is close to 150°C within 0.2°C. Adjust the potentiometer clock-
wise to increase the temperature or counter-clockwise to decrease the
temperature.
6. Set the set-point to 100°C and let it stabilize. Wait for the green ready LED
to light.
7. If the standard RTD or thermistor shows the temperature differs from 100°C
by more than 0.5°C but less than 1°C then adjust the potentiometer on the right
one-half turn at a time, waiting one to two minutes between adjustments, until
the standard RTD or thermistor shows the temperature is close to 100°C within
0.25 to 0.5°C. Do not force the temperature to exactly 100°C or the error at the
other two set-points will be excessive. If the temperature differs from 100°C by
more than 1°C then the instrument may require factory service.
8. Check the temperature once more at each of the three set-points.
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9 Calibration Procedure