Extech 380462 Precision Milliohm Meter, 220 V

Extech 380462 precision milliohm meter for four-wire resistance checks

The Extech 380462 is a portable precision milliohm meter for measuring very low resistances such as bonding straps, busbar joints, contactor and breaker contacts, cable terminations and motor winding connections. It uses four-terminal Kelvin clip leads to cancel the resistance of the leads and contacts, and it resolves down to 0.1 mΩ on its most sensitive range. The 380462 is the 220 V mains version; the 110 V model is the 380460.

It is housed in a compact field-service case with a protective cover and shows readings on a large 18 mm (0.7 in) LCD. A manual zero-adjust control and an overrange indication keep operation simple for a field technician.

Technical specifications of the 380462

The figures above are from the 380462 datasheet and user manual.

Why four-wire Kelvin measurement matters for the 380462

At milliohm level, the resistance of ordinary test leads and clip contacts can be larger than the resistance you want to measure. The 380462 avoids this by passing the test current through one pair of leads and measuring the voltage drop across the device through a second pair. The meter then calculates resistance from the voltage and the known current. Since the voltage-sense leads carry almost no current, the lead and contact resistance does not enter the result.

To get the best results, clip the current and voltage clips so that the voltage clips are inside the current clips, short the clips together to adjust zero before the measurement, and keep the clip jaws clean. The 200 mΩ range has its own selector switch, which the manual instructs the user to set before using that range.

Typical uses of the 380462

• Checking busbar joint and bolted connection resistance in switchboards and motor control centres during shutdowns.
• Verifying breaker and contactor contact resistance and comparing phases for imbalance.
• Testing bonding and earth continuity conductors where low-ohm confirmation is required.
• Measuring winding resistance of small motors and transformers on the 200 mΩ to 2 Ω ranges.
• Checking cable terminations and lug crimps after installation.

For currents above the 380462’s test level, or when a certificate-type DLRO test at 10 A is needed, an instrument such as the Extech UM200 micro-ohm meter, which has a 10 A maximum test current, is the next step.

Selection checklist for the 380462

• Confirm that the resistances to be measured fall between about 0.1 mΩ and 2 kΩ.
• Confirm your mains supply: 220 V for the 380462 or 110 V for the 380460.
• Decide whether a bench-top model with a comparator (380562) or a battery model (380580) suits the work better.
• Order a spare Kelvin clip test lead set (part 380465) if the leads see heavy use.
• Decide whether NIST-traceable calibration (the -NIST versions) is required.

Operation and care of the 380462

Connect the 380462 to the correct mains voltage, because the 110 V and 220 V versions are not interchangeable, and never apply voltage to the measurement terminals. Select the range, short the clips together, turn the zero adjust knob until the display reads zero, then attach the clips to the device or between two points in the circuit. De-energize and discharge any circuit before connecting. Clean the clip jaws, store the leads loosely coiled, and keep the instrument in its protective cover.

Because the meter is a field instrument, allow it to reach ambient temperature before use and recheck zero if the leads are changed.

Applications of the 380462 in Oman and the GCC

In switchgear and power plants, milliohm checks on bolted joints are a standard part of preventive maintenance, because a hot joint in a 40 °C switchroom runs hotter still. Oil and gas, petrochemical and desalination plants use low-resistance meters to verify bonding of pipework, tank earthing and cable glands, and to compare breaker contact resistance from one outage to another. Dust and heat call for a clean, dry storage case between jobs.

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Information to send with an RFQ for the 380462

• Part number 380462 and the required quantity
• Typical resistance range and the type of equipment under test
• Whether a spare Kelvin lead set (380465) or NIST-traceable calibration 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 380462 is attached on this page. It covers the 380460 and 380462 models.

Send us the part number 380462, 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.