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INTRODUCTION
The Field Strength Meter (FSM) has been designed as a high quality piece of test
equipment incorporating true RMS detection for evaluating the performance of
Audio Frequency Induction Loop Systems (AFILS) to the international standard IEC
60118-4.
It is simple to use with all types of installation from simple counter loops through to
low spill designs.
Three modes are available to investigate the key parameters of AFILS:
Background noise
to examine other magnetic noise
Field strength
to test system magnetic field strength
Frequency response
for measuring system bandwidth
The unit is designed to be used by holding it in the same position as the hearing aid
will be once the system is operational: i.e. hold the unit at head height to take
measurements: either seated, or standing depending on the venue.
A headphone socket and volume adjustment is provided to allow audible monitoring
and subjective testing of the system.
A test CD with 3 signals is provided for use with the meter. These are pink noise,
1kHz sine, and a combination signal which is made up of the other two.
Details of use are given in the AFILS test and commissioning procedure.
All you will need is an installed AFILS with a CD player fed into the appropriate
input, and a clear idea of the coverage area and intended listening positions. The
system commissioning certificate has been designed to help you note all the key
parameters.
For detailed analysis of systems such as ultra low spill configurations, you may
need more complex audio analysis tools such as an NTI Minilyzer used in
conjunction with the CMR3 probe.
For further information on loop design principles see ‘Designing Induction Loops’
handbook (supplied) or contact Ampetronic for advice.
SCC – Signal Connection Cables
These procedures require connecting an audio source to the audio inputs of a loop
system Ampetronic can provide a set of cables -SCC- to allow simple connection
from most audio systems to most loop systems. Contact us for details or search at
www.ampetronic .com.