Extech MA443 400 A True RMS AC Clamp Meter with NCV and Type K

Extech MA443 400 A true RMS AC clamp meter with NCV and Type K

The Extech MA443 is a 400 A true RMS AC clamp meter with a 30 mm (1.2 in) jaw for conductors up to 500 MCM, a non-contact voltage detector, a built-in flashlight and a Type K thermocouple input. It is the middle model of the MA440 series, which also includes the MA440 (AC, non-true-RMS) and the MA445 (true RMS AC/DC); the MA443 counts ten functions.

The multimeter functions include AC/DC voltage, resistance, capacitance and frequency, with a large backlit display, relative mode, data hold, Max/Min and an auto power off that can be disabled. The kit contains test leads, three AAA batteries, a pouch and a general-purpose Type K probe.

Technical specifications of the MA443

The figures above are from the MA440 series datasheet.

How the MA443 differs from other MA440 series models

Choose the MA443 when the loads include variable speed drives or electronic power supplies, because true RMS reads the distorted waveform correctly. If DC current is needed for batteries or automotive circuits, choose the MA445; if only basic AC current is needed, the MA440 is the economical choice.

Using the MA443 on motors and HVAC equipment

• Clamp one phase conductor at a time to read motor running current and compare with the nameplate.
• Use the capacitance range to check run and start capacitors on single-phase motors.
• Use the Type K input to record bearing, winding case or refrigerant line temperature while watching current.
• Use the NCV to find the live conductor before opening panels.
• Use Max/Min to see the swing in current during a cycle.

For 1500 A feeders or DC current, use the Extech MA1500; for a pocket 60 A clamp, use the MA63.

Selection checklist for the MA443

• Confirm maximum AC current is below 400 A and conductors fit a 30 mm jaw.
• Decide whether true RMS and Type K temperature are needed (MA443) or DC current (MA445).
• Check capacitor sizes: the MA443 range reaches 40 mF.
• Check availability of spare AAA batteries.
• Decide whether the -NIST calibration version is required.

Care of the MA443

Keep the jaw faces clean and fully closed, avoid dropping the meter, and clamp one conductor only. Remove the test leads from the meter when measuring current, since the leads and the jaw are separate inputs. The NCV indicates the presence of voltage but is not a replacement for a proper dead test. The general-purpose Type K probe does not cover the full range of the meter, so use a suitable probe for high temperatures.

Applications of the MA443 in Oman and the GCC

Electricians and maintenance teams at industrial plants and commercial buildings use a 400 A true RMS clamp for routine current checks on motors, pumps, fans and air-conditioning equipment, where the load is often drive-fed. Hot ambient conditions raise winding temperatures, so the Type K temperature function is useful to correlate current and temperature on bearings and terminals during site rounds.

Measurement technique with the MA443

Current readings depend on technique as much as on the instrument. Open the jaw, enclose a single conductor, centre it between the marks and close the jaw fully; a conductor held against the edge of the jaw can change the reading slightly. Keep other current-carrying conductors away from the jaw, since their fields add to the measurement. When checking a three-phase motor, measure all three phases and compare the highest and lowest values; an imbalance of more than a few percent suggests a supply, winding or connection problem that deserves investigation.

When measuring temperature with the Type K input, allow the probe to settle for a few seconds, attach it firmly to a clean surface, and use the relative mode to compare two points, for example the temperature of adjacent terminals on the same feeder. Log the current and the temperature together with the time, since a hot terminal under load is a stronger warning than a hot terminal at no load.

Information to send with an RFQ for the MA443

• Part number MA443 and the required quantity
• Maximum current and conductor size
• Whether a different MA440 series model (MA440 or MA445) is required
• Delivery location in Oman or the GCC and the required lead time
• Whether calibration documentation or a traceable calibration certificate is required

Documents and quotation

A datasheet for the Extech MA443 is attached on this page. It covers the MA440, MA443 and MA445 models.

Send us the part number MA443, the quantity and the delivery location in Oman or the GCC, and we will reply with availability and a quotation. Seven Star LLC is an independent supplier in Muscat and is not affiliated with the manufacturer.