Duncan Instruments Canada Ltd
Duncan Instruments Canada Ltd.
Electronic Measurement Solutions since 1968
ISO 9001


High Frequency Earth Meter TM-25M

Testing of the power transmission towers grounding (G) quality poses a serious problem as they are all electrically interconnected by means of Ground Wires which act as lightning rods, protecting the lines from atmospheric discharges.

Due to the existence of this connection, any attempt to measure a tower grounding (G) resistance using a conventional earth meter leads to wrong results as what is really being measured is all the shunt towers grounding (G) resistance (or, more precisely, its impedance at low frequency). Trying to disconnect the ground wire from an energized line is a risky operation due to the need for climbing to the tower highest part as well as for the proximity to the high-voltage conductors. TM-25m grounding resistance meter for high frequency 25kHz has been developed for such application.


  • Intended for measurement of earth resistance of electricity pylons
  • Minimizes the influence of adjacent pylons, connected by the guard calbe
  • Operation frequency: 25 kHz
  • Resistance Reading: Up to 300 Ohm
  • Automatic compensation of inductive component
  • Automatic current injection
  • USB interface
  • Built-in memory and printer
  • Rechargeable battery
  • Technical Specification
    MEASUREMENT RANGES Resistance: 0 - 300 Ohm
    Operation Frequency 25,000 Hz
    Test Current 20 mA automatic
    Inductive Component Compensation Through bank of capacitors integrated to the equipment Maximum capacity: 4.2 F Resolution: 10 nF
    Measurement Accuracy ±2.5 of reading ± 1 digit
    Display Alphanumeric display (LCD)
    Max. Earth Resistance of Auxiliary Rods 2,000 Ohm (Current rod); 2,000 Ohm (Voltage rod)
    Built-in Memory It allows for the storage of 2,000 tests readings in its internal NVRAM memory.
    Data Output USB
    Power Supply Internal or external rechargeable battery, 12 V. Internal battery autonomy: at least 2 hours
    Battery Charger For 100 ~ 240 V~ 50/60Hz
    Operating Temperature -5 °C to 50 °C
    Storege Temperature -15 °C to 75 °C
    Humidity Up to 95% RH (non condensing)
    Dimensions 340 x 295 x 152 mm
    Equipment Weight Approx. 4.9 kg
    Accessories Weight 16.5 kgs
    • 4x 50 cm long steel core rods with copper coating
    • 1x Rod extractor
    • 1x 70 m shielded cable 1x 50 m shielded cable
    • 1x 30 m cable to current rod
    • 1x 70 m cable to auxiliary potential rod
    • 1x 50 m cable to auxiliary potential rod
    • 1x Cable adapter for current electrode
    • 1x External battery cable
    • 1x Cable for connection to the unknown electrode (Tower)
    • 1x Case to carry accessories
    • 1x USB Cable
    • 1x Operating handbook

    Last modified February 15, 2007.
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