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How to Choose Which Ohm Scale to Use

In most modern consumer electronics, resistors cost pennies, yet without them, people couldn̵7;t use MP3 players, cellphones and other everyday gadgets. Service engineers faced with repairing electronic equipment often need to check individual components to identify where the problem lies, and a multimeter or ohmmeter is handy for taking measurements when fault-finding. Since the value of a resistor may be anything from a few ohms to several megohms, knowing which measurement range to select is essential for accurate readings.

Things You'll Need

Data sheets or circuit diagrams
Resistors for testing
Ohmmeter or multimeter

Instructions

- 1
  Read any available data sheets or circuit diagrams relating to the resistor that is to be tested. Note its nominal resistance if it is given.
- 2
  Examine the body of the resistor if you do not have any relevant documentation. If it is an axial resistor with color bands, use these to identify the nominal resistance. If not, check for any other markings that identify the nominal resistance.
- 3
  Switch on the meter in accordance with the manufacturer̵7;s instructions and set it to the lowest resistance range that exceeds the nominal resistance. For example, if the nominal resistance is 1.8 kilohm, and the meter has 200-ohm, 2-kilohm, 20-kilohm and 200-kilohm ranges, select the 2-kilohm range. If you do not know the nominal resistance, set the meter to the highest range.
- 4
  Connect the meter̵7;s test leads across the resistor. It does not matter which lead goes to which end of the resistor. Read the indicated resistance value from the display or meter.
- 5
  Switch the meter to the lowest resistance range that exceeds the indicated value if you started on the highest range. For example, if you started on the 200-kilohm range and the indicated value is 1.8 kilohm, switch the meter to the 2-kilohm range.
- 6
  Switch the meter to a higher range if the overload symbol displays. Check the manufacturer̵7;s instructions for the overload indication for your meter.
- 7
  Read the indicated resistance value once you have selected the appropriate scale. Record this figure if you wish.

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