This may be a very simple question. In my lab guide (I am a freshman Electronic Engineering student), we are supposed to build and analyze a circuit on a breadboard. First, we need to select some resistors for our circuit. The lab guide says: "To measure the resistors, set the multimeter to voltage mode". I am confused. Aren't we supposed to set it to resistance mode (with an ohm sign)?
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1\$\begingroup\$ The lab guide is wrong. Send in an edit to the author. \$\endgroup\$– Tony Stewart EE75May 4, 2018 at 7:40
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2 Answers
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There are several ways to measure resistance with a multimeter:
- Set it to resistance mode and get the value directly
- Apply a known current and measure the voltage across the resistor and calculate the resistance using Ohms law.
- Apply a known voltage and measure the current through the resistor and calculate the resistance using Ohms law.
If the only instruction you have is set it to voltage mode and measure the resistance, that is probably a wrong instruction.
For some resistors (potentiometers specifically) applying a known current might be a better way to measure the resistance as the wiper contact resistance could be rather large if the current is low and multimeters tend to use a low measuring current which would result in a wrong measurement.
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If the resistors are still loose on the bench then you need the resistance mode.
If they are « in circuit » and you need to measure the voltage drop and have the current flow through that resistor then you can calculate the resistance, so voltage mode.
It depends what the instructions tell you to do..
