Question { 12084 }

How to check range of DP Transmitter

Answer

The best part of answer is already mentioned in
above i.e DATASHEET as well as HART communicator.

If you want to use DP Tx for level of tank then
range of DP Tx will be get From C-C distance of tank from
tapping, by using simple formula i.e: (height * density=
range). It means you will get range of DP transmitter for
level.
If you want to get the range for Flow. in that
case please check the orifice plate which is already
installed in line, you will get the range.

Question { Invensys, 8282 }

why we use only 4 to 20ma other than 0 to 16 ma

Answer

Please give you attention below:

4 mA 0 %
8 mA 25 %
12 mA 50 %
16 mA 75 %
20 mA 100 %

at the time of no voltage (zero voltage) we get 0 mA
at the time of 24v dc supply we get 4 mA.
IF we keep the range starting from 0 mA we will get 0 mA at
the time of zero voltage & 24 V dc voltage supply which is
technically not good.
If your observation is too good that time you will
find that from above every gap between each other of 'mA'
& '%' the differrences are equally same.
see for mA : 0-4-8-12-16-20 (gap of 4 mA equally)
and see for % : 0-25-50-75-100 (gap of 25 % equally)
This things easily helpful to sort out the problems.

Therfore this STANDARDISATION is Universal.