# Multirange ohm meter design

In summary, designing a multirange ohm meter using a permenant magnetic moving coil movement involves using a D'Arsonval movement and a resistor in series or parallel to determine the range. A switch is then used to change the ranges. This type of ohm meter typically has a DC power supply and series resistance in order to measure resistance accurately. Digital ohmeters use a current source and measure the voltage across the probes to determine the ohms value.

Can someone help me to design the multirange ohm meter using permenant magnetic moving coil movement...

Can you give more info on the "permenant magnetic moving coil movement"?

We had to do this in school. Is this homework?

Can someone help me to design the multirange ohm meter using permenant magnetic moving coil movement...

One version is called a D'Arsonval movement.

The resistor in series (current mode) or parallel (voltage) determines the range. Figure the value of resistor to give you a range, then a switch to change ranges. Pretty basic stuff.

Integral said:
One version is called a D'Arsonval movement.

The resistor in series (current mode) or parallel (voltage) determines the range. Figure the value of resistor to give you a range, then a switch to change ranges. Pretty basic stuff.

He wants an ohmeter. What you've described (incorrectly) is used for measuring voltage and current as you stated. The resistor in parallel with the meter is used to measure current and is referred to as a shunt resistor. The series resistor is referred to as a multiplier resistor and this arrangement is used for measuring voltage.
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Typically an ohmeter that uses the d'arsonval meter movement has a DC power supply in series with the meter movement also in series with resistance to be measured. The power supply voltage and series resistor are varied to get the range wanted. Digital ohmeters will use a current source hooked directly to the probes and the voltage across the probes is measured and converted to an ohms value.