Polynomial Rtd; How To Use With Readwin® 2000 - Endress+Hauser iTEMP HART TMT162 Bedienungsanleitung

Appendix
104
11.2

Polynomial RTD

With "Polynomial RTD", the sensor is defined by a polynomial
4 3 2
(X4*x +X3*x +X2*x +X1*x
to 400 .
The 5 coefficients of the polynomial are calculated using the PC configuration software
®
Readwin 2000. There are two different ways of determining the polynomial:
• The sensor-matching-calibration
The deviation (compared to standard RTD) of the sensor or at the complete measuring
point (transmitter with connected sensor, Measured = T /°C or mA) is measured at
different temperatures (sampling points). By using a "weight factor" it is possible to set
special focus either on the given points (the deviation on the rest of the curve can be quite
high) or on the trend compared to the reference linearization (The sampling points are
only reference points of an e.g. aged sensor). These sampling points lead to a new revised
linearization, which is transferred to the iTEMP
• The customer specific linearization
The linearization is made by measured resistance or current values over the target
temperature range. These sampling points lead also to a new revised linearization, which
is transferred to the iTEMP
11.2.1 How to use with Readwin
Please refer also to the software documentation BA137R/09/en to configure the
device with the PC software ReadWin
1. Select POLYNOM RTD in Choice-field "Sensor type".
2. Press button LINEARIZATION to open module SMC32.
3. Default setting is Sensor-matching-calibration which can be recognized by "T/°C" in the
groupbox "Measured". Alternative choice is "Ohm" or "mA" for customer specific
linearization.
4. Default reference RTD linearization is Pt100. Check "Type of Sensor" if another RTD is
required. With customer specific linearization it is not possible to select "Type of Sensor".
5. "Weighting" default is 50%. As described above 100% means full focus on the accuracy
at the sampling points, 0% uses the sampling points as trend information for the
complete curve.
6. The "sampling points" can be edited in the shown table, default points are the min and
max temperature of the reference element. These values can be modified to a reduced
range.
7. To see the results of the new linearization use menu Calculate ... Calculate Curve and/
or Calculate ... Show Coefficients (Coefficients are shown in an extra form).
8. The red curve in the graph (scale on right) shows the deviation between calculated and
reference curve. This graph easily shows the effect of changing the "weighting".
9. When files exist, data can also be loaded (Data ... Load). Files made with older versions
(SW < 2.0) do only supply sampling points, the extra information ("Measured", "Type of
Sensor") has to be edited after loading data.
10. Storing all data in files use Data ... Save or Data ... Save as....
11. For using this functionality in the transmitter please press OK (data will be taken over
®
in Readwin 2000) and start to transmit to the device.
1
+X0) with 5 coefficients. The physical measuring range is 10
®
temperature transmitters.
®
temperature transmitters.
®
2000:
®
2000.
TMT162
Endress+Hauser