Image Credit: Allied Electronics, Inc. | Fotronic Corporation / Test Equipment Depot | OMEGA Engineering, Inc.

Clamp meters are ammeters that can measure current without the need to disconnect the wires where the measurement occurs. They provide information about current draw and current continuity in order to help users troubleshoot erratic loads and trends. High current flow may indicate a short circuit, an unintentional ground, or a defective component. Low current flow may indicate high resistance or poor current flow within the circuit.

Types of Clamp Meters

 There are two basic types of clamp meters: analog and digital. Both are designed to measure levels of alternating current (AC) and direct current (DC). Some clamp meters that measure AC current also measure root mean square (RMS) power, which is the square root of the time average of the square of the instantaneous power. Most products include a current sensor built into the clamp around the wire. Different types of clamp meters can measure different ranges of AC current, DC current, and AC current frequency. Some clamp meters are handheld and portable. Others are designed for benchtop or shop floor use. Battery-powered clamp meters can be operated without plug-in power and may be rated for outdoor use.

Special and Optional Features

Clamp meters may provide special measurement types or optional features. Some clamp meters can test diodes or transistors. Others can monitor thermocouples or resistance temperature detector (RTD) values. Programmable clamp meters provide internal data storage and allow users to establish activation triggers. They can also interface with computer hardware and software. In addition, products with external storage devices such as disc drives are available. With regard to optional features, clamp meters may adjust sampling rates automatically, display status information as a bar graph, and measure decibel (dB) readings. Mirrored scales make it easier to read analog clamp meters to a given accuracy by enabling operators to avoid parallax errors.

Specifications

Product specifications for clamp meters include output options and certifications or approvals. Output options for clamp meters include general purpose interface bus (GPIB), binary coded decimal (BCD), digital to analog (D/A), IEEE 488, and RS232. Clamp meters carry a maximum rating and are used in a variety of applications and industries. Underwriters Laboratories (UL), the Canadian Standards Association (CSA) and other organizations certify many of the clamp meters that are available today.