Using a Voltage Tester

• The most basic technique to determine low voltage is to use a voltage tester. A voltage tester consists of a small bulb and two insulated wires with metallic ends. Touch each end of the wire in different parts of the circuit to see if there is ample energy running through that part of the circuit, indicated by lighting up the bulb. A voltage tester can be useful in finding faulty outlets or where a fence shorts out in cattle pastures.
  
  

Using a Continuity Tester

• A continuity tester is similar to a voltage tester, but unlike the voltage tester it is used with the electricity to the current being tested turned off. A continuity tester consists of a battery and two wires: one terminating in an alligator clip and the other with a probe. Attach the clip and probe to various parts of the circuit to determine where the circuit is shorting out and experiencing low voltage.
  
  

Using a Volt-Ohm-Milliammeter

• A volt-ohm milliammeter, also called a "multitester," is a more common technique used to address more complex electrical situations. A multitester works the same as voltage testers and continuity testers, but it can give an actual reading of the electricity in the circuit in ohms. Attach the multimeter to the circuit the same way as other testers, with either alligator clips or probes. A multimeter can be used with the power to the circuit turned off.
  
  

Low Voltage Detect Microchips

• Many common products and appliances, such as smoke detectors and automobiles, have low voltage detect, or LVD, microchips in them that indicate when battery power is low. Detecting low power is as simple as watching for an LED or other indicator to become activated. Some microchips also conserve energy when the battery gets low. This is also important in safety devices that require constant power, such as electronic hospital bracelets.