BioProTT
TM
Flow Measurement System Version 1.00 page 36 of 75
7.7.1.2 Flow Value
The flow range of a sensor is linearly mapped to 4-20 mA in the following way:
1 - < 4 mA corresponds to negative flow, with 1 mA corresponding to the negative
flow value applying the same gradient as with the positive flow values. This means
the mapping of the negative flow into a current value is truncated at 1 mA.
4 mA equals zero flow
20 mA corresponds to the 1.5 x maximum flow of the specific sensor connected. See
the table below for the calculation of the specific conversion factors that need to be
applied.
The analogue interface is equipped with a 4-20 mA industry standard current loop. Make
sure that the voltage supply for the current loop is 24 V DC.
Diagram 1 shows the flow rate versus the output current for a sensor with a standard flow
range of 10000 ml/min.
Flow rate vs. Output current
-3000
-2000
-1000
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Diagram 1: Flow rate versus output current
To calculate an output current into the flow value (with adjusted calibration factor
accounted for), use the following equation:
Flow[ml/min]= (Current [mA]-4[mA])*Conversion Factor (max flow range)
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