FosMeter-Pro Induction Loop Test Kit



  • A must-have accessory for all AFILS installers and service engineers.
  • Simplifies the setup of an induction loop system to BS EN 60118-4 (Magnetic field strength in audio-frequency induction loops for hearing aid purposes).
  • Includes an FPRO Fosmeter Pro induction loop tester (c/w intuitive display and simple to follow test menus), a calibrated FPROSG Signal Generator (c/w pre-loaded test tones, voice and music samples) and a set of HEAD1 headphones.
  • Checks the magnetic field strength of an induction loop system and measures background noise, frequency response and metal compensation.
  • Loop listening circuitry allows subjective listening tests to be carried out using the headphones supplied.
  • Powered from a 9V PP3 battery.
  • Supplied in a protective canvas carrying case.
  • Auto power-off function helps to preserve battery life.


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By buying this product you can collect up to 27 loyalty points. Your cart will total 27 points that can be converted into a voucher of $5.40.

Technical Specifications

Compatibility Can be used to test any audio-frequency induction loop system to British and European performance standards.
Application/operation Download main instructions for details.
Quiescent current 25mA.
Max battery size and type Requires 1 x 9 V PP3 battery (non-rechargeable)
Indicators LCD display and Battery status indicator (FPRO & FPROSG).
Controls 2 x ‘soft’ buttons which change their function to suit the menu options being accessed (FPRO & FPROSG).
Connections 3.5mm audio output socket on FPRO for use with HEAD1 headphones; 3.5mm balanced line level output socket on FPROSG.
Product dimensions (mm) W 117 x H 79 x D 19mm (FPRO & FPROSG).
Construction & finish Plastic.
IP Rating IP20 (FPRO & FPROSG).
Weight 145g (FPRO & FPROSG).
Operating conditions/temperature The FPRO & FPROSG contain sensitive electronic equipment. They are designed for indoor use only and MUST NOT be subjected to conditions likely to affect their performance.
Notes Different amplifiers require specific audio connection leads. For PDA102, MLK1, and PDA200E amplifiers use an AL3 lead; for Pro-Range amplifiers use an AL14 lead.



Testing an induction loop system with the FPROK1 test kit is simplicity itself:-

First, connect the FPROSG signal generator to a suitable balanced line input at the AFILS amplifier using an AL test lead.

Next, switch on the amplifier and adjust the input signal control and loop drive current in accordance with the amplifier’s manual.

Finally, carry out the appropriate test (explanations are below) using the Fosmeter Pro tester, log the results on the certificate provided and proceed to the next test until all tests are completed. All of the tests should be carried out with the Fosmeter Pro in a horizontal (flat) position.

Background noise test
• Designed to ensure the background noise level of the site/system does not affect the intelligibility of the system in the covered area
• Detects the level of background noise and indicates if it is acceptable, tolerable or too high in accordance with BS EN 60118-4
• Measurements should be taken before and after the system is installed (the ‘after’ reading should be taken with the amplifier on and all inputs off)

Field strength test
• Designed to ensure the loop signal provides sufficient volume without distortion in the covered area
• Detects a pulsed 1kHz signal in accordance with BS EN 60118-4, calibrated at 400mA/m (0 dB L)
• Requires MP3 track 1 (1kHz sine wave)
• Use the amplifier’s gain/drive control to achieve a ‘good’ result

Frequency response test
• Designed to ensure good speech intelligibility in the covered area
• Detects 100 Hz, 1 kHz and 5 kHz in accordance with BS EN 60118-4
• Requires MP3 track 2 (frequency response sine wave)
• Presents all 3 results in an easy-to-read bar graph
• Acceptable results are +/- 3dB L from the central 1 kHz reference bar. If this cannot be achieved, use the amplifier’s ‘Metal Compensation’ control(if fitted) until an acceptable range is displayed

Metal compensation test
• Designed to ensure losses due to building structure and furnishings do not cause poor signal quality at high audio frequencies in the covered area
• Goes above and beyond the scope of BS EN 60118-4 but adheres to the recommended 3rd octave frequency spectrum advised in the standard
• Requires MP3 track 3 (metal compensation sine wave)
• An acceptable result is all the bars levelled out (if this isn’t the case, adjust the ‘metal compensation’ control on the amplifier – if fitted – until you are happy with the results).

Subjective listening test
• Designed to ensure hearing aid users receive an undistorted and clear signal in the covered area from the system’s actual inputs (music sources, microphones, etc)
• Requires a set of HEAD1 headphones plugged into the Fosmeter Pro’s headphone socket (ideally a hearing aid user should also test the signal using his or her own hearing aid but this is not always possible)
• Music and speech tracks are provided on the FPROSG signal generator if needed