Construction

• Ohmmeters are formed using built-in current sources, such as a battery, that is in series with current limiting resistors and a display. They operate by applying small voltages to the element they are measuring the resistance of.
  
  

Types

• They come in either analog or digital forms. Digital ohmmeters are the most common, and are found as either a standalone device or as a function in multimeters. They may be tabletop or handheld, which makes them flexible enough to be used in the home, lab, or out in the field.
  
  

Uses

• Ohmetro
  
  In addition to measuring resistance, ohmmeters may be used to check for continuity. Continuity tells you if your circuit is open or closed. Closed circuits are complete, and can conduct electricity. If the reading on the meter is infinity, the circuit is open and there is no continuity. If the reading on the meter is zero, the circuit is closed and has continuity.
  Ohmmeters help determine the quality of a component, such as op-amps or diodes, and are also used for electrical safety testing.
  
  

Application

• If you have a resistor you do not know the value of, take an ohmmeter and switch it to the lowest setting. Place one lead across each resistor, taking care not to touch the component or the leads with your fingers. Increase the setting on the ohmmeter until you receive a reading.
  
  

Warning

• Do not measure the resistance of a component inside a circuit with the power on. Always disconnect or remove the power source first, or remove the component from the circuit. If you do not, you will either obtain an incorrect reading or cause equipment damage, and you may be at risk for physical harm in some cases.