Sample implementation of a PTC sensor

The example below illustrates the implementation of a PTC sensor, in particular a platinum sensor (Pt sensor), based on the RTD table and according to DIN EN 60751.

Example for the implementation of a PTC sensor with the RTD lookup table

The general procedure is explained in chapter Lookup table. The example describes the implementation of table for a Pt500 sensor.

Description	Problem	Approach
For Pt sensors, tables with several 100 entries in 1°C steps are available.	Total number of interpolation points is exceeded. Currently, 100 interpolation points can be entered using the RTD table.	Limit the measuring range to correspond to 100 interpolation points in total Increase the step size, e.g. implement a table with 5°C or 10°C steps. Since the Pt sensor curves are almost linear, an increment value only has a small effect on the measuring accuracy. This is in contrast to NTC sensors, where the curve is exponential and a smaller increment is therefore preferable.
The manufacturer tables contain universal values	The table values should be adjusted to the specific sensor type	For different Pt sensors, the table entries have to be multiplied with the R₀ value. R₀ indicates the resistance at 0°C. The sensor designation is based on the temperature value.
		Pt sensor	R₀ (resistance at 0°C)
		Pt100	100
		Pt500	500
		Pt1000	1000

For the Pt500 sensor, the following CoE entries can be selected and edited with the following XML file (Download: ZIP):

CoE Entry	Entry
0x8001:01 Distance in Degrees	10
0x8001:02 Amount of Entries	60
0x8001:03 Start Temperature	-40
0x8001:04 Conversion Factor	10
0x8001:05 Value 1	4247
0x8001:0x further table entries	.....

Example for the implementation of a PTC sensor, programmable according to DIN 60751 for Pt sensors

The implementation according to DIN EN 60751 is described in the section Programmable_according_to_DIN_60751_for_Pt sensors. The parameters A, B, C are already stored in the CoE. Only the temperature range and the R₀ parameter for the specific sensor need to be added. R₀ indicates the resistance at 0°C. The sensor designation is based on the temperature value. The CoE entry has to be adjusted for the specific sensor.

Pt sensor	CoE Entry 0x8003:03
Pt100	100
Pt200	200
Pt500	500
Pt1000	1000

Comparison of implementation via RTD table and according to DIN EN 60751

If we now compare the course of the resistance values as a function of temperature, by the RTD table and according to DIN EN 60751, it becomes clear that both implementation methods provide almost the same result. Due to the easier implementation, the parameterization according to DIN 60571 is preferable.

Sample implementation of a PTC sensor 1: — Comparison of Pt500 sensor implementation