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10. Program
10-4
10.2 Example of Programming 2 (Offset adjustment)
The resistance temperature detective itself has an built-in error, therefore an offset error may occur
in temperature conversion data. An offset error occurs due to the change with the passage of time
also. An example of correction by programming in this case is shown below.
However, because an actual offset value is not always a specified value, it cannot be corrected
completely. The offset error refers to the deviation of any temperature conversion data from the
reference value(Note) in a specified rate. (The offset error means the constant deviation from the
reference value.)
Example of offset
(1) Adjustment procedure
(a) Decide whether an offset error is on + or – side toward a reference value.
(b) Obtain a temperature conversion data corresponding to offset error.
Offset error Temperature conversion data
1 ºC H0028 or H002C
2 ºC H0050 or H0054
3 °C H0078 or H007C
4 °C H00A0 or H00A4
5 °C H00CC or H00D0
(c) If offset error is on + side toward the reference value, subtract the value obtained in (b) from
the temperature conversion data. If it is on – side, add the value obtained in (b) to the
temperature conversion data.
(2) Example of programming (The configuration is the same as the example of programming 1)
If the channel 2 has + 2 °C offset, subtract H0050 from the temperature conversion data WX0042.
Temperature conversion data
A: Offset error
Reference
value
- side offset
+ side
offset
EH-150
temperature
conversion data
Note: Measure a reference value using a
measuring device with a higher
accuracy than EH-PT4. Or connect a
resistor with a high accuracy instead
of the resistance temperature device
and obtain a direct offset error. For the
relationship between the temperature
and resistance, see Table 7.2.
WR0000 = WX0040
WR0001 = WX0041
WR0002 = WX0042 - H0050
WR0003 = WX0043
Temperature(ºC)