Handbook
November 2011 / 59-UMC0071 / Issue 01
Mercury iTC
Page 82
GETTING STARTED
Original Instructions
If two known temperatures are available it is possible to make small adjustments to the
scale and offset of the standard curve to match a particular sensor. The process can be
used with either PTC and NTC sensors.
The adjustment is applied to the measured parameter, so for a resistance sensor the
adjustment is applied to the measured resistance.
For best results the scaling adjustment should be applied at the high-parameter end and
the offset at the low-parameter end. So for a NTC resistance sensor, apply the scaling at
the known low-temperature point (ideally near the high-resistance end of the range). If a
scale adjustment of more than a few percent is required to correct the temperature
reading, investigate the measurement set-up to check there is not some other error
present.
Once the scaling adjustment has been made, change to the low-resistance end of the
range and make the offset adjustment (for an NTC resistance sensor, this is a high-
temperature point). Again this should be a small adjustment. As these adjustments are
not independent, re-check the high-resistance point after the offset has been adjusted. A
few iterations of these adjustments may be required to achieve the desired accuracy.
Procedure for using a generic calibration file
You need a method of maintaining the temperature sensor at two known temperatures
(T1 and T2) to perform this calibration. This procedure calibrates the sensor for
temperatures between these two known values.
For this procedure, T1 produces a lower sensor-resistance than T2:
For a PTC sensor, T1<T2.
For an NTC sensor, T1>T2.
1 Tap a configured panel on the Home page. The Sensor Details page is displayed.
2 Tap the Calibration field and select Generic from the drop-down menu.
3 Tap Cal Adj.
4 Place the sensor in a location with temperature T1.
5 Adjust the Offset value to produce the required Scaled Parameter value.
6 Place the sensor in a location with temperature T2.
7 Adjust the Scale value to produce the required Scaled Parameter value.
8 Repeat steps 4 to 7 until a calibration of the required accuracy has been obtained.
9 Tap Save to apply the new calibration.
5.4.3 Configuring a heater
1 Double-tap a configured panel on the Home page. The Channel Display
Configuration page is displayed.
2 Tap Pair. The Device Pair Configuration page is displayed.
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