﻿ 4-20mA Formulas and Examples | Instrumentation Formulas

# 4-20mA Formulas and Examples

4-20 mA transmitter current output can be converted to the voltage within a specified range, from 0 to a maximal amplitude Vmax, as shown in the following picture:

## 4-20mA Formulas Calling I the output current and V the Voltage—or other physical variables (PV) —between Vmin (which is usually 0) and Vmax; the conversion formulas are as follows:

• #### PV [units] = ( (I − 4 ) / 16) × ( PVmax − PVmin ) + PVmin

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 0-5V. calculate the equivalent 4-20mA current value.

I =  ( ( (VVmin) / ( VmaxVmin) ) × 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 4-20mA. Calculate equivalent voltage. consider 0-10V is the output voltage range.

V = ( (I − 4 ) / 16) × ( VmaxVmin ) + Vmin

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 0-1500 m3/hr. Calculate the equivalent flow rate value.

PV = ( (I − 4 ) / 16) × ( PVmaxPVmin ) + PVmin

PV = ( (16.5 − 4 ) / 16) × ( 1500 − ) + 0

PV = 1171.87 m3/hr

Also Read : 4-20mA Transmitter Principle

### 13 thoughts on “4-20mA Formulas and Examples”

1. Thanx, Realy it is important for me.

Reply
2. Thanks very much sir, this is very important.

pls how do i print it.

Reply
3. formula wrong ex: range -50 to 50 psi i get 12 mA what is the pv value?

Reply
• Hi Balajee, Formula Working fine. Please see : PV = [ (12-4)/16 X { 50- (-50) } ] + (-50) = ( 0.5 X 100 ) – 50 = 0. Also Click Here to Use online Calculator for fast calculations.

Reply
• yes Mr S Bharadwaj reddy its by mistake. Thanks 4 reply

Reply
• I(mA)=16/(Vmax-Vmin)(V-Vmin)+4Vmax/(Vmax-Vmin)

Reply
4. How amazing very good effort.

Reply
5. thank you brother

Reply
6. how to calculate the % of valve opening at milli ampere 4 to 20

Reply
7. Thank you infomation.

Reply
Send this to a friend