10 Best Clamp Meters | March 2017
- data hold feature saves measurements
- includes a 2 year warranty
- compact size good for small tool bags
- rugged overmolded grip
- rotary dial mode select switch
- cat iii 600v safety category rating
- capacitance zero and offset adjustment
- auto power off to conserve battery life
- expensive but high quality
- includes a soft vinyl carrying case
- comes with detachable test leads
- has a maximum reading mode
- audible continuity sensor
- has a low-battery indicator
- auto selects appropriate operating range
- analog bar lcd display
- over range protection for all ranges
- has a hold measurement feature
- has a relative zero function
- continuity beeper identifies shorts
- diode test can find voltage drops
AC Clamp Meters Versus DC Clamp Meters
Clamp meters are available in both AC and DC models. A standard clamp meter used to measure AC currents cannot be used to measure DC currents and vice versa. This is because AC and DC currents have different properties. In an AC current, the flow of electricity periodically reverses direction causing a dynamically changing magnetic field. A DC current continuously flows in one direction and has a fixed magnetic field.
AC clamp meters are designed to detect the dynamically changing magnetic field produced when electricity flows through a wire. The fluctuations in the magnetic field caused by the AC current switching directions is directly proportional to the size of the current flow. A transformer inside of the AC clamp meter can detect and measure the magnetic fluctuations and convert those measurements into a current reading.
DC clamp meters makes use of a Hall Effect sensor to measure currents. The Hall Effect principal states that when a current carrying conductor is placed in a perpendicular magnetic field, the magnetic field will exert a transverse force on the charge carrier, which is perpendicular to both the current and the magnetic field. A small voltage runs across the Hall element when it is subjected to this transverse force, which is then amplified and measured to produce a current reading.
How To Use A Clamp Meter
Using a clamp meter is a relatively simple endeavor that does not require you to break a circuit or make a direct connection to any live wires. This makes it the ideal tool for the home DIYer who is still learning how to work with electrical components.
Your first step is to choose the electrical conductor you will be testing. It must be a live wire that is currently under load. If using it on an appliance, this means the appliance should be in operation during testing. If you have purchased a clamp meter which does not have autoranging, you will then need to select the correct measurement function and range. If unsure of the voltage range, it is always best to select a higher range and then decrease as needed.
Next, clamp the jaws of the meter around the conductor you are measuring. The jaws of the device should not be touching the conductor on any of its sides. If there are a number of other wires jumbled around the conductor you are measuring, you will need to untangle them so your clamp meter is only encircling the conductor to be measured. A reading should appear on the meter's display screen within seconds.
What To Consider When Buying A Clamp Meter
Not all clamp meters are created equal and it is important to purchase a quality clamp meter that will provide accurate results in the types of environments where you will be working. One of the first and foremost considerations must be accuracy of the readings. Ideally you should purchase a clamp meters that reports true-rms readings. If not, extraneous electrical noise from light bulbs and other devices in the room can cause inaccurate readings. In addition to offering a true-rms reading, your clamp meter should meet the industry accuracy standard of 2% ± 5 counts. Steer clear of any accuracy ratings stated to ± 10 counts.
Nearly every clamp meter can perform admirably in a clean and controlled lab setting, but more than likely you won't be working in this type of environment. Look for a clamp meter that is designed to work in the kinds of conditions you will be subjecting it to. Some may be specified for indoor use only with minimum and maximum operating temperatures. If you use a clamp meter under or over its specified operating temperatures, your readings will be inaccurate.
Finally, you will want to look at the features of each clamp meter you are considering. It may seem like a no-brainer to go with one that offers the most additional features, but bear in mind that the more gadgets integrated into a clamp meter, the harder it may be to use for its intended application. Avoid clamp meters that have silly features like a tape measure. Instead, focus on purchasing one with the measurement functions you need to get the job done quickly and correctly.
Some useful features to keep an eye out for include Inrush measurement capabilities, which can be invaluable if you will be working on motors, autoranging, and a large blacklit display screen with a wide viewing angle.