Calibration of Universal Temperature Inputs

(adcunv4c)

General

Products which utilise Universal temperature inputs, Fan Coils, Actuator controllers, Secondary Controllers may now have their sensor channels calibrated at the factory prior to shipment. The automatic calibration routine is in the firmware and aims to calibrate the sensor input at 25 deg C. This results in the temperature readings across the input range being much more accurate.

Expected accuracies based on a sample of 10 boards are:-

range 10 to 30 deg C +/- 0.3 deg C

range 0 to 80 deg C +/- 0.6 deg C

Operation

In production this calibration will be carried out automatically as part of the Booking out test procedure. The following description details how to replicate the process using Doorway. This may be necessary if the firmware has been changed in the field.

For best accuracy you will need at least one precision (0.1% or better) 10K resistor, the process is faster if a resistor is available for each input.

1. Check that the product firmware code ends in 4c1 or later which indicates that the calibration code is available and that the product uses universal input scaling (not Zone Controllers or Boilers at present).
2. Fit 10K resistor to each input to be calibrated
3. Set Doorway to display the test page for the product, this should have ACH1, ACH2 ...for number of channels (config C170-), and TEST data point (C120) displayed.
4. Wait until the channels to be calibrated have settled showing a value around 25 +/- 2 deg C
5. Set TEST (config C120) to 242. See later for selecting individual channels.
6. Watch the channels being calibrated, as each channel is calibrated the value of TEST will reduce by the 'component value' of that channel. Channels which are not reading within 23 to 27 or are not set for temperature will be ignored. When the readings are within +/- 0.03 of 25.00 deg C on all channels the calibration will terminate and the controller will be reset.

Notes

It is possible to choose various options by the choice of the TEST parameter. The table gives the meaning of each component, add all the required components to arrive at the TEST value.