How to use the ammeter shunt resistor calculator
Find the shunt resistor that extends a meter movement to a larger full-scale current. Enter meter resistance, meter full-scale current, desired full-scale current in the fields above; the shunt resistance, current multiplier are computed instantly and plotted on the chart so you can see how the answer changes.
Common searches this calculator answers include “ammeter shunt”, “extend meter range”, “shunt resistor calculator”, “calculate ammeter shunt resistor”, “find shunt resistance”.
Formula
Variables
- Rm — Meter resistance (Ω)
- Im — Meter full-scale current (mA)
- Ir — Desired full-scale current (A)
Worked example
With meter resistance = 50 Ω, meter full-scale current = 1 mA, desired full-scale current = 1 A, the calculator gives shunt resistance ≈ 0.05005005 Ω; current multiplier ≈ 1,000 ×.
Frequently asked questions
What is the ammeter shunt resistor calculator used for?
Find the shunt resistor that extends a meter movement to a larger full-scale current. It helps with questions such as “ammeter shunt”, “extend meter range”, “shunt resistor calculator”.
What is the formula for the ammeter shunt resistor calculation?
Shunt resistance (Ω) = Rm × (Im / 1000) / (Ir-Im / 1000). Current multiplier (×) = Ir / (Im / 1000). Here Rm is meter resistance (Ω), Im is meter full-scale current (mA), Ir is desired full-scale current (A).
What inputs do I need for the ammeter shunt resistor calculator?
You need meter resistance in Ω, meter full-scale current in mA, desired full-scale current in A. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use the ammeter shunt resistor calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the ammeter shunt resistor result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.