Appendix D
D-2
Calibration Traceability
resistance is first provided to calibrate the ohmmeter which is used to
measure the RTD probe. The probe is then checked at 0 °C, using the ice
bath described earlier. Since the output of the probe is nearly linear and
the ratio of the probe resistance at 49.90 and 0 °C is inherently very
stable, any offset in the output of the probe noted at 0 °C can be used to
correct the measurement at 49.90 °C. The calibration fixture is then set to
49.90 °C with the probe, and the resistance of the thermistor is measured
at 49.90 °C.
The thermistor is inserted into the condenser block again (filled with
water, and air flowing), and the LI-610 temperature display is set to
49.90 °C. The span potentiometer in the LI-610 is adjusted until the
thermistor resistance is the same as it was when inserted in the calibration
fixture.
Specifications
Zero Set Point
Ice Bath:
Resolution: 0.0006 °C using thermistor.
Accuracy: ± 0.02 °C.
Noise: < ± 0.0015 °C.
Repeatability: < ± 0.002 °C.
Condenser:
Resolution: 0.0006 °C using thermistor.
Accuracy: ± 0.03 °C.
Noise: < ± 0.002 °C.
Repeatability: < ± 0.003 °C.
Stability: < ± 0.01 °C.
Span Set Point
Calibration Fixture:
Resolution: 0.0007 °C using thermistor.
Accuracy: ± 0.03 °C.
Repeatability: < ± 0.01 °C.
Condenser:
Resolution: 0.0007 °C using thermistor.
Accuracy: ± 0.05 °C.
Noise: < ± 0.002 °C.
Repeatability: < ± 0.003 °C.
Stability: < ± 0.01 °C.
