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Formula to Calculate 3-15psi from 4-20mA Current

The amount of psi can also be calculated from the amount of the milliamp signal, or one can calculate the amount of the milliamp signal when the amount of psi is known. Each of these signals has an offset and a span that must be taken into account for the calculation.

The offset for the milliamp signal is 4 mA, and the span is 16 mA. The span is determined by subtracting the lower value from the higher value (20 mA – 4 mA). The offset for the psi signal is 3 psi, and the span is 12 psi (15 psi – 3 psi).

The formula for converting between these two systems is shown in the following equation. The milliamp signal is identified as “I” and the pressure signal is identified as “P”. When one is converting from one to the other, either “I” or “P” will become a known value in the formula.

The value 4 in the left side of the equation represents the 4 mA offset, and the value 16 represents the 16 mA span. The value 3 in the right side of the formula represents the pressure offset, and the value 12 represents the 12 psi span.

(I – 4)/16 = (P – 3)/12

The formula can be further simplified as shown in below figure

Formula for 4-20mA from 3-15PSI

Example:

Calculate the equivalent amount of air pressure for a current signal of 17.5mA ?

P = ((I – 4)/16) x (12) + 3

P = ((17.5 – 4)/16) x (12) + 3

P = 13.125 psi

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9 comments

maqsood February 6, 2016 at 6:55 pm

very nice and so easy for understood.

Reply
sudhesh February 8, 2016 at 3:36 pm

mai to mureed to gaya is side ka thanks to all

Reply
moss August 22, 2016 at 6:10 pm

hi, its easy to understand, thanks,,,..! i need one more help . if sensor outputs 4-20mA then controller takes in it and converts it to counts lets say 162 it displays. how can i convert to mA and then to pressure in bar please advice.

Reply
S Bharadwaj Reddy August 23, 2016 at 7:14 am

Hi, Please Click here to read the similar article which have the same numerical conversions.

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NISHIL PARMAR August 29, 2016 at 10:36 am

Very nice and usefull app

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Noor Mustafa August 8, 2017 at 8:38 pm

use full app

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sudhesh katare September 15, 2017 at 3:14 pm

plz post the derivation of formula that how to calculate the formula

Reply
S Bharadwaj Reddy September 15, 2017 at 3:48 pm

Hi, Its already posted (similar), check old posts from “Formula” category

Reply
Sarfraj alam August 7, 2019 at 2:55 pm

Very good app

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Formula to Calculate 3-15psi from 4-20mA Current

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