420 mA transmitter current output can be converted to the voltage within a specified range, from 0 to a maximal amplitude V_{max}, as shown in the following picture:
420mA Formulas

I [mA] = ( ( (V − V_{min}) / ( V_{max} − V_{min}) ) × 16 ) + 4

V [Voltage] = ( (I − 4 ) / 16) × ( V_{max} − V_{min} ) + V_{min}

PV [units] = ( (I − 4 ) / 16) × ( PV_{max} − PV_{min} ) + PV_{min}
Where,
I is the current,
V is the voltage,
PV is the Process Variable
min is the Lower Range Value of the respective signal
max is the Upper Range Value of the respective signal
Note that the values and units of min and max are units must be same.
Example 1 :
A Analog output card gives an output voltage of 2.5V and its overall range is 05V. calculate the equivalent 420mA current value.
I = ( ( (V − V_{min}) / ( V_{max} − V_{min}) ) × 16 ) + 4
I = ( ( (2.5 − 0) / ( 5 − 0) ) × 16 ) + 4
I = 12 mA
Example 2 :
A transmitter output range is 13.5mA and its output range is 420mA. Calculate equivalent voltage. consider 010V is the output voltage range.
V = ( (I − 4 ) / 16) × ( V_{max} − V_{min} ) + V_{min}
V = ((13.5 – 4)/16 x (10 – 0 ) + 0
V = 5.9375 V
Example 3 :
A Flow transmitters output current is 16.5mA and its range is 01500 m3/hr. Calculate the equivalent flow rate value.
PV = ( (I − 4 ) / 16) × ( PV_{max} − PV_{min} ) + PV_{min}
PV = ( (16.5 − 4 ) / 16) × ( 1500 − 0 ) + 0
PV = 1171.87 m3/hr
Also Read : 420mA Transmitter Principle
13 comments
Thanx, Realy it is important for me.
Thanks very much sir, this is very important.
pls how do i print it.
formula wrong ex: range 50 to 50 psi i get 12 mA what is the pv value?
Hi Balajee, Formula Working fine. Please see : PV = [ (124)/16 X { 50 (50) } ] + (50) = ( 0.5 X 100 ) – 50 = 0. Also Click Here to Use online Calculator for fast calculations.
yes Mr S Bharadwaj reddy its by mistake. Thanks 4 reply
I(mA)=16/(VmaxVmin)(VVmin)+4Vmax/(VmaxVmin)
0 psi
How amazing very good effort.
thanks
thank you brother
how to calculate the % of valve opening at milli ampere 4 to 20
Hi, For 420mA to 0 – 100 % Conversion : CLICK HERE
Thank you infomation.