TestEquity 106 - How to Verify the Calibration

Chapter 7 – Maintenance
TestEquity 106 & 107 Temperature Chamber Page 7-5
How to verify the calibration
! CAUTION: TestEquity does not recommend performing the controller calibration
procedures unless you have verified that the controller is actually out of
calibration.
TestEquity recommends verifying the calibration before attempting to actually perform a
calibration. The microprocessor-based instrumentation used in TestEquity chambers seldom goes
out of calibration. If you try to calibrate the instrumentation before determining that calibration is
necessary, you may make it worse if done incorrectly.
Variations in temperature throughout the chamber interior are NOT a measurement of controller
accuracy. These variations, called “gradients”, are a function of the physical design of the
chamber and its airflow, the characteristics of the test sample, and how it is oriented in the
chamber. You cannot “calibrate” to improve gradients. The common practice of measuring
multiple points in the chamber and adjusting the temperature controller’s calibration to correct
for these errors is incorrect! The correct way to adjust what the temperature controller “displays”
compared to what is measured at some point other than the controller’s sensor, is with the
“Calibration Offset” parameter. The F4 or F4T Temperature Controller User’s Manual for
details. Calibration verification should be performed with the Calibration Offset set to 0.0 (zero).
Total system accuracy in the chamber includes the controller plus the thermocouple wire
accuracy. Total system accuracy over the chamber’s operating range is typically ±1.55°C, ±1
LSD or a theoretical total of ±2.55°C. The easiest way to verify the instrumentation accuracy is
with an independent calibrated temperature sensor and display. Place the sensor inside the
chamber, near the chamber’s conditioner fan grille. If the readings agree within the specified
limits, then no calibration adjustments are necessary.
For the F4 Controller: If calibration of the temperature controller is necessary, refer to the “F4
Temperature Controller User’s Manual”.
For the F4T Controller: If calibration of the temperature controller is necessary, refer to the “F4T
Touch Screen Controller User’s Guide”.