How To Use A Multimeter

How To Use A Multimeter


Preface: This article hopes to help guide you on to utilize a multimeter. There is a large variety of multimeters out there from basic to complex, so be sure to read your specific meter's manual to understand how to set it up properly.



Safety First


Important Safety Notice


      Injury, death, loss of property, fire, electric shock, malfunction, reduced performance & machine life, and critical failures can result from not reading, understanding, and following instructions and best practices.


      The machine must only be operated by trained and authorized personnel. The scopes of competence for the different activities in the scope of operating the machine must be clearly defined and observed, so that under the aspect of safety, no unclear questions of competence occur. 


      This applies in particular to activities on the electric equipment, which must only be performed by qualified . For all activities concerning installation, set-up, start-up, operation, modifications of conditions and methods of operation, maintenance, inspection and repair, the switch-off procedures that may be provided in the Operation Manual must be observed.



Voltages Present in Thunder Equipment


      There are many hazards to be aware of when working with our machines. You will be dealing with 110V AC 60Hz , 48VDC, 36VDC and 24VDC as well as +-15VDC power supplies.   The Nova series machines with water-cooled DC excited glass tubes utilize a high voltage DC power supply (Laser Power Supply, LPSU) that is capable of outputting 30,000V DC at 30mA and more. The LPSU Output (big red wire) should NOT be metered. That wire is big, red, and scary for a reason.


Warning
Power supplies will typically have capacitors in them which can store voltage and take time to dissipate. Take proper precautions when working around them.




How To Use A Multimeter


Video Overview:



Here are some tutorials and other resources on the proper operation of an auto-ranging digital multimeter. Please observe all safety information and best practices. 


Basic overview of a meter. Your meter will likely be different so you will need to read your manual.

Function
Craftsman 82139 Meter
1. Digital screen. Will show you units and value of the measurement. Be sure to take note if it is showing VAC, VDC, Ohms and whether it is set to Auto range

2. Buttons that can be used to adjust the function of the meter. Generally they are tied to where you have the meter dial set to

3. Meter dial. Used to set your meter into the mode for what you plan to measure. Your dial may have sections for VAC, VDC and OHMS with pre-set ranges that you need to specifically select.

4. Probe positions. The probes can be set to read Voltage/Ohms and other functions or high Amp current. Generally, you will only need to use the selection for Voltage/Ohms. Some meters have fixed probes.



Example of 120VAC Testing:


Meter dial is set to VAC, this meter will Auto Range but the user could select a range, typically 200, if needed. The probes are in the COM and V selection for measuring voltage as shown.

Common places to measure AC Voltage:
  1. Relay Output Contacts for Fan and Air Pump
  2. Chiller Power Cable
  3. Input Power for Machine
  4. DC Power Supply Inputs
  5. LPSU Power Input


Setup
Measurement

In this setup, we are measuring the 120v feeding the Chiller Power Supply.

Example of 24VDC Testing:


Meter dial is set to VDC, this meter will Auto Range but the user could select a range, typically 200, if needed. The probes are in the COM and V selection for measuring voltage as shown.

Common Places to Measure VDC:
  1. Relay Coil
  2. TL Timer
  3. Red Dot
  4. DC Power Supply Output
  5. Chiller Water Pump input

Setup
Measurement

In this setup, we are measuring the 24VDC output of the chiller power supply.


Example continuity testing:


Info
Continuity testing is generally done with the power off and the terminations removed\unplugged as we look for a break in the wire/circuit.

You can pick and choose which meter lead goes to which end, the black and red color do not matter for this test. All readings should be low Ohms, like less than 10.

Common Places to Measure Continuity:
  1. Signal Wires
  2. Power Cables End to End
  3. Control Wires End to End


Meter Setup
OHM Reading


In this example, continuity is being checked on the chiller power cable from one end to the other.


More Resources

Here are more resources on meters:


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