A ThermistorInputPoint is a NumericPoint with NdioResistiveInputProxyExt configured for a UI to read a thermistor temperature sensor. It is pre-configured with a linearCalibration extension, for offset correction. For details, see Linear Calibration Ext.
A ThermistorInputPoint is the same as a ResistiveInputPoint, only with a different “Conversion” setting in its ProxyExt. However, the Ndio Point Manager and ndio palette both list this point separately, so it is covered here separately.
The point’s Proxy Ext contains common Ndio Proxy Ext properties. Among those properties, note that the read-only “Device Facets” is preset to ohms.
Depending on the type of thermistor temperature sensor you are using, you can select a Conversion type of either Type 3 Thermistor, or any other using a Tabular Thermistor conversion.
Table 1 shows the hard-coded response curve used if ProxyExt property Conversion is set to “Thermistor Type 3”:
Table 1. Type-3 Thermistor Ndio Curve
| Ohms | Deg. C |
|---|---|
| 0 | 165 |
| 610 | 110 |
| 1060 | 90 |
| 1690 | 75 |
| 2320 | 65 |
| 3250 | 55 |
| 4620 | 45 |
| 6240 | 37 |
| 8197 | 30 |
| 10000 | 25 |
| 12268 | 20 |
| 15136 | 15 |
| 18787 | 10 |
| 23462 | 5 |
| 29462 | 0 |
| 37462 | -5 |
| 47549 | -10 |
| 61030 | -15 |
| 78930 | -20 |
| 100000 | -25 |
In the ProxyExt of the thermistor point, if you select Conversion type of “Tabular Thermistor,” an edit control (note pad icon) appears in the property sheet beside it. Click the icon to see the Tabular Thermistor dialog, as shown in Figure 20.
This dialog allows you to edit the current ohms-to-degrees Celsius curve used by the proxy point, import another thermistor curve (.xml file), or export (save) the current thermistor curve as an .xml file. In this way you can provide any custom thermistor curve needed.
The following notes apply to using this feature:
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A curve requires at least 2 points (rows), each using ohms to degrees Celsius values.
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Points are used in ascending order, by the ohms column.
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You can add as many points as is needed (there is no hard-coded limit). Click the button to add a new row for a point.
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If you skip a point, just add it at the end, and then click . This automatically reorders all points in ascending order, by the ohms column.
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Click the delete icon (trash can) beside any point to delete it from the curve. If you click the button, all points (plus any Description text) is removed (typically, you do this only to enter a new thermistor curve).
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Description text appears in the ProxyExt property sheet, beside the Conversion edit icon.
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When you click , the curve configuration is stored as part of the conversion object in the station (there is no association with any external file, in case you imported a thermistor curve).
If you update a thermistor curve (say, add a point) after importing it into one or more Ndio points, you need to import it
in those points again, in order for them to be updated.
Related to this, see Curve File Import/Export notes.
As needed, import (load) or export (save) a thermistor or non-linear curve file in xml format using the and buttons in either the Tabular Thermistor Dialog (Figure 20) for a “Tabular Thermistor” conversion, or Tabular Conversion Dialog (Figure 13) for a “Generic Tabular” conversion.
When you do this, the standard Niagara File Chooser dialog appears, as shown in Figure 21.
To import a thermistor curve file, you can navigate under your “My Modules” folder to the xml folder in the kitIo module (Jar) file (if available, see Figure 21). If the kitIo module is not available, navigate to the xml folder in the ndio module (Jar) file.
Or, you can navigate to any other location you have a thermistor curve file. Import any other saved, custom non-linear conversion .xml files the same way—see Non-linear sensor support.
As of the date of this document, the kitIo module contains an xml folder with five (5) different thermistor curves in xml format, as follows:
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precon_type_2_model_24.xml— For Precon type 2 model 24 sensor -
precon_type_4_model_42.xml— For Precon type 4 model 42 sensor -
rs271_0110.xml— For Radio Shack sensor model 271-0110 -
te6300_10k— For TE-6300 10K type sensor -
type_3.xml— For standard Type-3 Thermistor sensor
Upon any curve file import, all existing thermistor or non-linear curve configuration for that Ndio proxy point is overwritten (replaced by configuration in the imported file). A confirmation dialog advises you of this before you import, as shown in
Figure 22
To export a curve .xml file, use the File Chooser to navigate to any location you wish to save the current thermistor curve configuration, and supply a File Name. You can use this saved .xml file in the configuration of any other like Ndio proxy point, whether in this station or another station.