IM-P343-37 CTLS Issue 4
30
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SP400 Electropneumatic Smart Positioner
9.3.2 C-CAL - current calibration
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Programming notes
C-Cal provides a simple way to make a fine calibration of the input current signal (4 - 20 mA).
To perform the calibration:
1.
Enter C-CAL and press the key, then press the key.
2.
Generate a 4 mA input signal and press
3.
Generate a 12 mA input signal and press
4.
Generate a 20 mA input signal and press
If 'ERROR' is displayed the calibration routine is aborted. The value of the generated signal is too far from
the expected one. Be sure that a 4 mA, 12 mA or 20 mA signal is generated as required. Press to return
to C-CAL.
If 'OK' is displayed the calibration has succeeded. Press to return to C-CAL.
Where possible current calibration should be overtaken, to guarantee a perfect match between the input current
generated and the reading of the SP400.
Let’s assume that the table below show the input signal generated by a PLC or DCS versus the input signal
read by the SP400.
Setpoint Input current from PLC Current read from SP400
0% 3.6 mA 3.8 mA
50% 12 mA 12.2 mA
100% 20 mA 20.2 mA
Hence when the setpoint is 0% the PLC generates a 3.6 mA instead of 4 mA.
After C-CAL is executed the SP400 recalibrates the current read to compensate the error.
Setpoint Input current from PLC Current read from SP400
0% 3.6 mA 4 mA
50% 12 mA 12 mA
100% 20 mA 20 mA
In this way a perfect match is achieved between the setpoint of the PLC and the setpoint of the of the SP400
(i.e. the input current read by the SP400).
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