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FSM Field strength meter

The FSM Magnetic Field Strength Meter from Ampetronic is a cost effective and simple solution for measuring, setting up and commissioning an induction loop system to the requirements of IEC60118-4. The meter is an ergonomically designed hand held instrument for measuring loop system performance. There are three calibrated operational modes for the assessment of Background Noise, Field Strength and Frequency Response as required to ensure correct function of the loop system. The meter also doubles as a loop listener, with a headphone output to listen to the signal in the loop.

The meter is supplied in a soft case  and with  full operating instructions including a guide to commissioning. The Ampetronic FSM can be used to monitor, set up or commission any induction loop system regardless of the manufacturer or type.

Applications include

  • Accurate set-up and commissioning
  • System monitoring and maintenance
  • Site surveys
  • Certification to IEC60118-4
  • Assessment of frequency losses due to metal
  • Assessment of loop coverage and overspill
  • Assessment of background noise

Included Accessories

  • Soft carry pouch
  • User guide/handbook
  • Commissioning Certificate (template)
  • Batteries

Optional Accessories

Set of cables to easily interface audio inputs to loop systems (order code SCC)

Product Code:

  • Features
  • Specifications
  • Downloads
    • Simple assessment of any system to
    • Three modes of operation for three test types
    • A-Weighted background noise • Broad band mode (50Hz – 8kHz)
    • Frequency response (100Hz, 1kHz, 5kHz)
    • True RMS detection calibrated to
      400mA/m = 0dB
    • Wide viewing angle LED display
    • Colour coded LEDs for simple readout
    • Resolution to 1dB
    • Head phone output with volume control
    • Ergonomic, rugged, light weight construction
    • Soft carry case
    • 5 year warranty
  • Background Noise

    To determine the level of the background magnetic field present in the intended location for the loop system. Also used to measure low level signals to assess overspill outside a loop system.

    • A-Weighted filter
    • True RMS detection referenced to 400mA/m
    • Scale -42 to -12dB
    • Audio (headphone) output is post filter for monitoring

    Field Strength

    A broad band measurement to measure field strength delivered by the system.

    • Broad band measurement 50Hz to 8kHz
    • True RMS detection referenced to 400 mA/m
    • Scale -22 to +8dB with 1dB intervals from -3 to +6dB
    • Suitable for use with sine wave, pink noise, or combination signals (provided), or any other real signals

    Frequency Response

    Third octave filters for measuring performance across the required frequency spectrum as required by IEC60118-4.
    Used to confirm adequate power at high frequencies as required for good intelligibility. Used to assess frequency dependent loss due to metal structures, and to optimise frequency compensation.

    • Third octave bands at 100Hz, 1kHz and 5kHz
    • True RMS detection
    • Scale resolution to 1dB
    • For use with pink noise only (signal provided)
    • Audio (headphone) output is post filter


    Magnetic field measurement

    Coil orientationVertical when unit held upright
    Reference level400mA/m (In Field strength mode)
    Frequency response50Hz to 8kHz ±0.25dB
    30Hz to 10kHz -3dB
    Gain stabilityBetter than 0.5dB over all conditions


    DisplayFlying spot LED bar graph with wide viewing angle
    Colour coded (green for -3dB to +3dB)
    Audio (headphone)16Ω min (32Ω per side)
    3.5mm stereo jack connector


    Battery2 x AA alkaline (supplied)
    Battery monitorBattery OK when LED illuminated
    Battery lifeUp to 100hrs use, dependent on use pattern


    Dimension84 x 27 x 140mm (meter only)
    Weight150g excluding batteries
    Operating environment-10 to +45°C
    10 to 85% RH

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