Back to basics: How to measure electricity with a clamp meter

Fluke Corporation
Tags: hand tools, power tools, maintenance and reliability

A clamp meter is an electrical tester that combines a basic digital multimeter with a current sensor. Clamps measure current. Probes measure voltage. Having a hinged “clamp” jaw integrated into an electrical meter allows users to simply clamp around wire, cables and other conductors at any point in the electrical system and measure its current, without disconnecting it.

What do clamp meters measure?

  • Clamp meters measure any of these: AC current, AC and DC voltage, resistance, continuity, and, with some models, DC current, capacitance, temperature, frequency and more
  • Typically measure to the nearest tenth of a unit (rather than the milli-units you find in a full-function multimeter), making them perfect for electrical work

Who uses them?

  • Industrial maintenance technicians
  • Control technicians
  • Electricians – in-house and contractors
  • Facilities, building maintenance and HVAC technicians
  • Service organizations

What are they used on?

  • Industrial equipment
  • Industrial controls
  • Electrical systems
  • Commercial/industrial HVAC

What do they use them for?

  • Service: Repairing existing systems on an as-needed basis.
  • Installation: Troubleshooting installation problems, performing final circuit tests and supervising apprentice electricians while installing electrical equipment.
  • Maintenance: Performing scheduled and preventive maintenance on electro-mechanical systems.

Why use a clamp meter?
Industrial situations often call for simultaneous measurement as part of troubleshooting, so many of those users carry two meters: one to measure electrical current and one to measure voltage. For electricians, a clamp meter is a quick and versatile diagnostic tool for figuring out why an electrical system or piece of equipment is not operating correctly.

What’s inrush?
Large machinery often requires a big surge of electricity to get started – electricians have to make sure the rest of the system can support that occasional big surge in demand. That surge is called inrush and it causes other problems than just overall supply. Fluke clamps use proprietary technology to filter out electrical “noise” and capture the starting current exactly as the circuit protection sees it.

What’s different about the new clamps?
The flexible coil and the extended measurement ranges help solve these common issues:

  • Tight cabinets and bundled wires that make it difficult to use a regular clamp meter.
  • Large or awkward conductors a regular clamp meter can’t get around to measure.
  • Needing a co-worker’s help to get a measurement.
  • Wanting to measure more than 1,000 amps AC.

Where to learn more
The following Fluke Web site, www.Fluke.com/Motors_Drives, lists clamp meter ABCs, application notes, case studies, a discussion board, videos and other resources that help explain how to use clamp meters for troubleshooting motors.