Using a DVOM to measure voltage

Part 1. Preparation and safety

Objective

• Use a DVOM to measure voltage.

Personal safety

Whenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies. Among other items, this may include:

• Work clothing – such as coveralls and steel-capped footwear
• Eye protection – such as safety glasses and face masks
• Ear protection – such as earmuffs and earplugs
• Hand protection - such as rubber gloves and barrier cream
• Respiratory equipment - such as face masks and valved respirators

If you are not certain what is appropriate or required, ask your supervisor.

Safety check

• Make sure the hood stay rod is secure.
• Always make sure that you wear the appropriate personal protection equipment before starting the job. It is very easy to hurt yourself even when the most exhaustive protection measures are taken.
• Always make sure that your work area/environment is as safe as you can make it. Do not use damaged, broken or worn out workshop equipment.
• Always follow any manufacturer's personal safety instructions to prevent damage to the vehicle you are servicing.
• Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks. If you are unsure of what these are, ask your supervisor.

Points to note

• DVOM stands for Digital Volt Ohm Meter.
• DVOMs come in many forms. Always follow the specific manufacturer's instructions in the use of the meter, or serious damage either to the meter and/or to the electrical circuit could result.

Part 2: Step-by-step instruction

1. Set up the meter for a voltage check
   Prepare the Digital Volt Ohm Meter or DVOM for testing voltage by inserting the black probe lead into the “common” input port, and the red probe lead into the “Volt/Ohms” input port.
2. Check the meter function
   Turn the rotary dial until you have selected the mode for “Volts DC”. The reading on the meter should now be at Zero. Some meters will automatically sense the correct voltage range when a voltage is detected. On other meters you will have to set the voltage range before using the meter.
3. Check the voltage of a battery
   Place the Black probe onto the Negative terminal of the battery, which will be marked with a Minus sign, and place the Red probe onto the Positive terminal of the battery, which is marked with a Plus sign.
4. Interpret the results
   Note the voltage reading from this 12-volt battery. If the battery is fully charged the meter will give a reading that is 12.6 volts or more. If it is NOT fully charged the reading will be less than 12.6 volts.