Dear all,
My application is flow measurement using DP Tx.When we want to calculate the mA output from dp transmitter

Do we have to calculate the mA output based on % of dp value or % flow corresponding to that particular dp.

As you know 25% of deltaP corresponds to 50% of flow.Then while providing the mA output in Alarm & trip schedule based on which value we have to calculate mA value.

Thanks in advance.

Regards,
GB

 

DP transmitters are available with linear or square root outputs. Smart transmitters can be configured either way. A linear transmitter would have an output of 8.00 mA at 25% of the full scale DP. A square root output would give you 12.00 mA at 25% of full scale DP.

 

Hi GB,
You are using DP TX to measure flow, probably because you have an orifice or similar device.

You are interested in a mA signal which is indicative of your flow.

So you have to use the square root function to get the flow. In other words when you apply 50% of DP, you must read 25% current or 8mA. The chart below was copied from a popular spread sheet and hope it shows properly in all email clients. I use this chart as a ready reference in order to avoid human error while doing calibration or witnessing it. Hope it helps you.
Or remember 4,5,8,13,20 for sq. root instead of 4,8,12,16,20 which is for linear.

Linear DP in % Flow = Sq. Root of Dp in % mA indicating flow
0 0 4
5 0.25 4.04
10 1 4.16
15 2.25 4.36
20 4 4.64
25 6.25 5
30 9 5.44
35 12.25 5.96
40 16 6.56
45 20.25 7.24
50 25 8
55 30.25 8.84
60 36 9.76
65 42.25 10.76
70 49 11.84
75 56.25 13
80 64 14.24
85 72.25 15.56
90 81 16.96
95 90.25 18.44
100 100 20


Regards,
Anand Iyer
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