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Extech MG300: 13 Function Wireless True RMS MultiMeter/Insulation Tester

MultiMeter/1000V Insulation Tester with Wireless PC interface (915MHz)

The MG300 is a True RMS multimeter with built-in insulation resistance tester with the added safety of wireless data streaming for remote monitoring and data logging. By adding insulation testing capabilities to the ubiquitous digital multimeter, electricians are always equipped for insulation testing, helping make it a more routine part of predictive maintenance with faster troubleshooting and repairs without additional tools. The rugged and waterproof (IP67-rated) combination meter includes a digital insulation resistance tester (or megohmmeter) with 4 different test voltages for measuring resistance up to 4GΩ with 0.001MΩ resolution. Complete with remote receiver with USB cable, windows compatible software, heavy duty test leads, alligator clip test lead, type K bead wire temperature probe with adapter, carrying case, and 6 x AA batteries.



  • Wireless USB interface transmits measurement data to a PC
  • Backlit super large triple display
  • 125V, 250V, 500V, and 1000V test voltages
  • Insulation Resistance from 0.001MOhm to 4000MOhm
  • Auto discharge of capacitive voltage
  • Lock Power On Function for hands-free operation
  • Data Hold, Min/Max, Relative mode, Auto power off
  • Complete with USB receiver, Windows® software, test leads & alligator clips, bead wire temperature probe, carrying case and batteries
  • USA, Mexico, and Canada use 915MHz model MG300 and majority of other countries use 433MHz model MG302


Specifications Range Resolution Basic Accuracy
Insulation Resistance 4MΩ, 40MΩ, 400MΩ, 4000MΩ 0.001MΩ ±3%
Insulation Test Voltages 125V, 250V, 500V, 1000V
AC/DC Voltage 1000V 0.1mVAC/ 0.01mVDC AC: ±1%, DC: ±0.06%
AC/DC Current 10A 0.1µA AC/ 0.01µA DC AC: ±1.5%, DC: ±1%
Resistance 40MΩ 0.01Ω ±0.3%
Capacitance 40mF 0.001nF ±3.5%
Frequency 100MHZ 0.001HZ ±0.1%
Duty Cycle 0.1 to 99.9% 0.01 ±1.2%
Temperature -58 to 2192°F (-50 to 1200°C) 0.1°F (0.1°C) ±1% + 4.5°F (2.5°C)
4-20mA% -25 to 125% 0.01%
Continuity/Diode Yes
Dimensions/ Weight 7.8 x 3.6 x 1.9″ (200 x 92 x 50mm)/ 20.5oz (582g)


MG300_English Datasheet

MG300_English User’s Manual

MG300_CE Declaration of Conformity