Extech MG320 CAT IV Insulation Tester and True RMS Multimeter

Extech MG320 CAT IV insulation tester with true RMS multimeter

The Extech MG320 combines a 1000 V insulation resistance tester and a true RMS multimeter in one handheld unit, so a technician can prove that a circuit is dead, test its insulation, and log the result without changing instruments. The insulation function offers five test voltages from 50 V to 1000 V, reads up to 20 GΩ, and adds PI and DAR modes, a programmable timer, a step-voltage test and a pass/fail comparison mode.

The multimeter side measures AC/DC voltage up to 600 V and resistance with continuity, and the whole instrument carries a CAT IV 600 V safety rating. Up to 99 readings can be stored and recalled manually, which suits maintenance rounds where results are written into a report later.

Technical specifications of the MG320

How the MG320 adds value over a basic insulation tester

A basic tester gives one number. The MG320 gives a process: set the voltage, run a timed test, calculate PI or DAR automatically, compare the result with a threshold you programmed, and store it. The comparison mode is useful when a maintenance procedure says that a motor must show at least a given number of megohms; the technician enters the limit and the display shows a pass or fail without mental arithmetic.

The step-voltage function raises the test voltage in 10% steps from 50% to 120% of the selected range. A sound insulation system shows a fairly constant resistance as voltage rises, while a damaged or contaminated system shows a falling resistance at the higher steps. This makes the step test a quick way to expose weaknesses that a single spot test would miss.

Using the MG320 for motor and cable testing

• Use the lock power on function to run a timed test hands-free and read the result at the end.
• Test at 50 V or 100 V for sensitive electronics and instrument cabling where a higher voltage could damage components.
• Use 500 V for 400 V motors and 1000 V for 690 V motors, and compare against the stored last reading for the same asset.
• Switch to the multimeter function to confirm zero voltage before connecting the insulation leads.
• Store the reading with its memory number and write that number in the job card.

For 5 kV or higher test voltages the MG320 is not the right tool; choose the Extech 380395 or MG500. For a simple 1 kV tester without a multimeter, the MG310 is the compact choice.

Selection checklist for the MG320

• Confirm that the maximum test voltage you need is 1000 V.
• Check that the 20 GΩ range is adequate for your equipment.
• Decide whether true RMS multimeter functions and CAT IV 600 V rating are needed in the same instrument.
• Decide whether the comparison mode, timer and step voltage are required by your procedures.
• Confirm whether 99 manual memory locations are enough, or whether you need a logging instrument.

Safety, care and calibration for the MG320

Always isolate and lock out the equipment, verify it is de-energized with the multimeter function, and keep the clips on until the stored charge has discharged. The instrument discharges the test signal automatically after the test. Replace batteries when the low battery icon appears, use the specified fuse, and keep the leads in good condition. Clean with a damp cloth and avoid solvents. Because the MG320 is IP 40 rated, it should not be used in wet conditions.

Calibration and repair should be performed by qualified service personnel, and an instrument used for acceptance records should be calibrated at the interval your quality system requires.

Typical applications of the MG320 in Oman and the GCC

Electrical maintenance teams in oil and gas, power and water plants use a combined insulation tester and multimeter for motor starter checks, pump motor tests, heater circuit checks and cable verification during shutdowns. In high-temperature switchrooms and humid coastal sites, the stored readings and comparison mode help technicians to apply the same acceptance limit to every motor and avoid disputes with contractors. The soft case and light weight suit rounds across large process areas.

Information to send with an RFQ for the MG320

• Part number MG320 and the required quantity
• Voltage range and acceptance criteria used in your maintenance procedure
• Required spare leads, batteries or fuses
• 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 MG320 is attached on this page. It lists the test voltages, ranges and features for the model.

Send us the part number MG320, 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.