HT Instruments M71 Digital Earth Resistance Tester 1004030

Electrical contractors and maintenance technicians who verify earthing systems on residential, commercial, and industrial installations will find the HT Instruments M71 a dependable tool for three-pole earth resistance measurement. Its voltammetric method delivers stable readings even in the presence of interference, while the backlit LCD keeps values visible in dim distribution rooms or outdoor switchyards.

Key specifications

• Measurement method: 3-pole voltammetric
• Earth resistance range: 0.00 Ω to 1999 Ω
• Earth resistance resolution: 0.01 Ω
• Earth resistance accuracy: ±(2% + 2 digits)
• Ground voltage range: 0 to 200 V AC
• Ground voltage resolution: 0.1 V
• Ground voltage accuracy: ±(1% + 2 digits)
• Test current frequency: 82 Hz
• Display: LCD with backlight
• Power supply: 6x 1.5V AA batteries
• Battery life: approximately 500 measurements
• Auto power off: after 5 minutes
• Data hold function: yes
• Operating temperature: 0°C to 40°C
• Safety rating: CAT III 200V
• Protection class: IP40

Why choose it

The M71 combines a wide earth resistance range with a dedicated ground voltage check, allowing you to confirm the absence of stray voltage before starting a measurement. Its compact size and battery operation make it easy to carry between job sites, and the auto power-off helps preserve battery life during long working days.

Ideal use cases

• Testing earth electrodes for lightning protection systems
• Verifying grounding of electrical panels and machinery
• Commissioning new installations according to local codes
• Periodic maintenance of earthing systems in industrial plants

Good to know

The instrument operates at an 82 Hz test frequency, which reduces the influence of mains harmonics on the measurement. It is powered by six standard AA batteries, so replacements are readily available on site.