Solutions for Every NeedA clamp meter is an electrical tester that combines a voltmeter with a clamp type current meter. Like the multimeter, the clamp meter has passed through the analog period and into the digital world of today. Created primarily as a single purpose test tool for electricians, today’s models have incorporated more measurement functions, more accuracy, and in some instruments, some very special measurement features. Today’s clamp meters have most of the basic functions of a Digital Multimeter (DMM), but with the added feature of a current transformer built into the product.
The ability of clamp meters to measure large ac currents is based on simple transformer action. When you clamp the instrument’s “jaws” around a conductor carrying ac current, that current is coupled through the jaws, similar to the iron core of a power transformer, and into a secondary winding which is connected across the shunt of the meter’s input. A much smaller current is delivered to the meter’s input due to the ratio of the number of secondary windings vs. the number of primary windings wrapped around the core. Usually, the primary is represented by the one conductor around which the jaws are clamped. If the secondary has 1000 windings, then the secondary current is 1/1000 the current flowing in the primary, or in this case the conductor being measured. Thus, 1 amp of current in the conductor being measured would produce 0.001 amps or 1 milliamp of current at the input of the meter. With this technique, much larger currents can be easily measured by increasing the number of turns in the secondary.
Buying a clamp meter not only requires looking at specifications, but also looking at features, functions, and the overall value represented by a meter’s design and the care taken in its production. There are many types of clamp meters. Choosing the one that best suits your applications is important. A brief overview follows, for a more in-depth look see 5 things to consider when buying a clamp.
- Use a basic clamp meter to ensure all three phases on your feeders are pulling the same current.
- An advanced clamp meter with some logging capability, will help you resolve intermittent breaker trips.
- You might need a specialized clamp meter that can accurately measure motor inrush current. You’ll want a specialty clamp if you do motor maintenance on production conveyor motors, HVAC motors, and plant air compressors, knowing motor inrush current is crucial for keeping these systems running.
Clamp Meter Application NotesYou might find these application notes helpful in determining when to use a clamp meter and which one to choose.
Clamp Meter ABC's (.pdf) »
There are two types of current clamps commonly available: "average responding" and "true-rms". Learn more about each and which would best serve your needs.
DMM vs Clamp Meter (.pdf) »
What is a clamp meter and what can it do? What measurements can be made with a clamp meter? How do you get the most out of a clamp meter? Which clamp meter is best suited to the environment the meter will be used in? The answers to these questions will be found in this application note.
True-rms (.pdf) »
We all know it's costly not to have the right tools for the job. If you've been in this business a while, you've managed to accumulate a variety of screwdrivers. Why not just one screwdriver? Because you are already practicing the concept of having the right tool for the job - even with a tool as simple as that. So, it makes good sense to apply this same concept to your measuring tools.
Learn More About Our Complete Line of Clamp MetersView the clamp meter selection chart (.pdf) »
Need Help Choosing the Right Clamp Meter for Your Application?Use the online clamp selector guide »