Measurement Computing CB-COM-7012 - Manual (Page 69)

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CB-7012, CB-7014, CB-7017 User’s Manual
amplified.
Two-wire transmitters typically output a 4 to 20 mA cur-
rent output signal. One wire is for power input, the other is signal
output.
Three-wire transmitters typically supply a 0 to 5V voltage
output signal. One pair of wires is for power input and ground and
the third wire is the signal output.
3.8 Linear Mapping
A linear mapping function translates the input value to a
desired output value. Linear mapping is a algorithm that converts
an analog input value into a percentage, digital, or engineering-unit
value.
Linear mapping does the following:
Converts source low value (SL) to target low value(TL);
Converts Source high value(SH) to target high value(TH).
For an input value(AI), the output value is:
If AI < SL, output value =
−
19999. (under-limit).
Else if AI > SH, output value = +19999. (over-limit).
Else output value = (AI
−
SL)/(SH
−
SL) * (TH
−
TL) + TL
For example, if we connect a temperature transmitter to
CB-7014/14D, suppose the sensor output is 4 mA when the input
temperature is 0 deg C. and 20 mA when the temperature is 100
deg C. To read the temperature directly, we must convert the
source values of 4.0 to 20.0 mA to target values, 0 to 100 deg C.
Suppose the CB-7014/14D is Address 01, the baud rate is
9600 bps, and no-checksum.