Setra Blog

How to Convert mA to Voltage

Written by Tom Lish | December 14, 2021

Converting mA to voltage is common in HVAC when working with pressure transducers. Terminology to keep in mind includes:

  • 1 mA = 0.001 AMP (short for amperes)
  • Amps are referred to as CURRENT
  • Resistor values are in OHMS (Ω is the symbol for ohms)
  • VOLTAGE is the result of passing amps through a resistor

 

 In order to change mA (current) to voltage, you need to pass the current through a resistor.

The formula for voltage is:

E = IR
E stands for volts, I stands for amps, and R stands for resistance

 

In control circuits, the most common resistor values are 250Ω & 500Ω, although any value can be used depending upon the device.

If your control circuit is using a 250Ω resistor:
mA Amps x Resistance Volts
4 0.004 x 250Ω 1
5 0.005 x 250Ω 1.25
6 0.006 x 250Ω 1.5
7 0.007 x 250Ω 1.75
8 0.008 x 250Ω 2.0
9 0.009 x 250Ω 2.25
10 0.010 x 250Ω 2.5
11 0.011 x 250Ω 2.75
12 0.012 x 250Ω 3.0
13 0.013 x 250Ω 3.25
14 0.014 x 250Ω 3.5
15 0.015 x 250Ω 3.75
16 0.016 x 250Ω 4
17 0.017 x 250Ω 4.25
18 0.018 X 250Ω 4.5
19 0.019 x 250Ω 4.75
20 0.020 x 250Ω 5
If your control circuit is using a 500Ω resistor:
mA Amps x Resistance Volts
4 0.004 x 500Ω 2
5 0.005 x 500Ω 2.5
6 0.006 x 500Ω 3
7 0.007 x 500Ω 3.5
8 0.008 x 500Ω 4
9 0.009 x 500Ω 4.5
10 0.010 x 500Ω 5
11 0.011 x 500Ω 5.5
12 0.012 x 500Ω 6
13 0.013 x 500Ω 6.5
14 0.014 x 500Ω 7
15 0.015 x 500Ω 7.5
16 0.016 x 500Ω 8
17 0.017 x 500Ω 8.5
18 0.018 x 500Ω 9
19 0.019 X 500Ω 9.5
20 0.020 x 500Ω 10