AnalogIn calculation principle
When Analogue input channels are configured to measure: 0-20mA / 4-20mA / 0-100mV, all analogue measurements are internally scaled into a floating-point value between 0 and 1.
The lowest transmitter signal equals 0 and the maximum transmitter signal equals 1.
Minimum transmitter signal is: 0 mA or 4 mA or 0V
Maximum transmitter signal is: 20 mA or 100 mV
If the transmitter signal is below the measurement range the value is negative.
If the transmitter signal is above the measurement range the value is greater than 1.
The calculation of AnalogIn is based on 2 constants per channel:
ZeroPoint: Process value for the minimum signal from the source transmitter
Span: Process value for the source transmitter’s measurement range.
(Maximum process value = ZeroPoint + Span)
AnalogIn is calculated using this formula:
AnalogIn := (Value * Span) + ZeroPoint
(See also: AnalogIn, Span, ZeroPoint)
Example of converting a 4-20mA signal to a measurement value (AnalogIn) of 2 to 5 Bar:
Transmitter error compensation
PD 640 Application Notes (mA)
PD 641 Application Notes (Pt100 / Pt 1000)
PD 642 Application Notes (mV / thermocouple)