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Field Strength Meter Handbook (UP14301-13)

From https://assistivelisteningknowledgebase.org/evidence/ampetronic-fsm-handbook/ · record checked 13 October 2026

  • Ampetronic

Manufacturer (Ampetronic, maker of the FSM and hearing loop systems)

Summary

A loop-meter manual separating magnetic field, frequency response and background-noise measurements, with specifications and recalibration advice.

Key findings

  • Pages 2-4 describe a true-RMS meter with field-strength, frequency-response and background-noise modes, plus headphone monitoring. The measurement reference is 400 mA/m; the frequency-response mode compares 100 Hz, 1 kHz and 5 kHz bands using pink noise.
  • Page 14 states a field-strength scale of -22 to +8 dB and an A-weighted noise scale of -42 to -12 dB, both relative to 400 mA/m. It specifies 125 ms RMS detection, field-mode response of 50 Hz to 8 kHz within ±0.25 dB, and overall gain change below 0.5 dB.
  • Page 6 requires representative measurement positions and heights, taking telecoil orientation into account. The meter senses the component parallel to its coil axis; the other axes are not measured.
  • Page 9 warns that the 100 Hz pink-noise reading can be unstable and asks for its peak reading. Page 11 notes that a narrow-band spill measurement needs a different scale correction, and that more detailed spill/noise work may require an audio analyser with a CMR3 probe.
  • Page 12 checks the actual programme sources and comfortable, undistorted sound. Page 13 says low batteries extinguish the power indicator and leave the unit outside calibration.
  • Page 15 says factory calibration is valid for one year from shipment, recommends initial recalibration after that year, and allows a longer period if no adjustments are needed.
  • Pages 6-9 ask users to mark measurement points on a floor plan and record background-noise, field-strength and frequency-response results at the defined points. Each procedure names the required meter mode and test signal, providing the setup details needed to repeat a measurement.

Limits

Manufacturer specifications and procedures, without independent error measurements or a complete uncertainty budget. The stated gain change and frequency-response tolerance are not a universal absolute-accuracy figure. No manual publication date is printed; March 2022 dates the declaration on page 15, not necessarily this handbook revision.

Read the original

www.ampetronic.com/wp-content/uploads/UP14301-13-HB-FSM-A5-format.pdf

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Cite this source

Ampetronic. Field Strength Meter Handbook (UP14301-13). n.d. https://www.ampetronic.com/wp-content/uploads/UP14301-13-HB-FSM-A5-format.pdf (accessed 13 October 2026).

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