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502 010 05
P-NET SWNo. 12: TCFlow
In addition to the normal flow measurement, the Flow Transmitter also measures a tem-
perature, which may then be used to calculate a temperature compensated flow.
The calculation of the temperature compensated flow is performed to compensate for the
expansion of the liquid as a function of the liquid temperature.
The Flow Transmitter automatically calculates the temperature compensated flow by multi-
plying the flow rate by a temperature dependent correction factor, K.
The temperature compensated flow, TCFlow, may be read directly in this register.
The relationship between temperature and K is stored in the Flow Transmitter and is shown
below.
Implementing an automatic calculation of TCFlow in the entire temperature range requires
a Pt100 temperature sensor to be connected to the terminals 9, 10, 11 and 12.
K
1.00
0.99
0.98
0.97
0.96
0.95
0
10
32
50
Temperature compensation may be implemented for liquids at fixed temperature without
using a Pt100 temperature sensor. This is shown in the following example:
The liquid is at a fixed temperature of 75 ° C during production. No Pt100 sensor is
connected, but temperature compensated flow is required for the volume counters.
The value for the correction factor K is read from the above diagram, 0.975. This
value should now be multiplied by the value from SWNo. 20 (PD 210: E1 ), Meter-
size and then stored back in Metersize. The Code2 register, digit 4 should be set to
1 in order to select Flow as data for volume counters.
Note:
Using this kind of temperature compensation will only give the correct result when
the liquid is at the fixed temperature.
30/55
20
30
40
50
68
86
104
122
Flow Transmitter, PD 340
PD 210 display key: T.C.FLOW
60
70
80
90
140
158
176
194
Tempe-
rature
100
° C
212
° F
551 113 01
Manual
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