The GMA305 Seismophone was originally developed to cater for the needs of cable fault
location technicians where simplicity of use and high accuracy is of utmost importance in
noisy environments.

The instrument is equipped with a number of filters, which greatly simplifies the acoustic pinpoint
location of faults. It is also equipped with a number of other user-friendly features to simplify the
procedure. Display of information is done in bar graph fashion.


Principles of Operation
The instrument embodies the very latest DSP (Digital Signal Processing) techniques, which greatly
broadens the possibilities to upgrade and modify the instrument by simply updating the software.
This means that whenever new technology is developed it will become available to you as the owner
of the instrument. The acoustic amplifier employs five different filters to filter as much noise as
possible before the signal is amplified. The magnetic amplifier is gain adjustable which allows the
operator to attenuate the magnetic signal and then pinpoint exactly where the cable is. It also
employs distance measurement techniques, which measure the time difference between the
acoustic and magnetic amplifier.

The display is of a 128 x 64 graphical LCD display. Automatic Magnetic Gain Adjustment feature �
The instrument is set up in Auto Magnetic Gain mode by �memorizing� the cable depth. Auto power
shut down feature - Instrument shuts down after 5 min of no user interaction.

Backlight also switches off after 30 seconds, if no user interaction.
GROUND MICROPHONES : GMA305
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SPECIFICATIONS
Filters





Distance
Measurement
Range


Display












Acoustic
Amplifier

Acoustic
Indication

Dimensions

Weight

Power Supply
ACCESSORIES
.
A: 50 � 1000 Hz
B: 150 � 700 Hz
C: 150 � 1000 Hz
D: 300 � 2000 Hz
E: 700 � 3600 Hz

1: 0 � 4 m
2: 0 � 20 m
3: 0 � 60 m
4: 0 � 410 m

128x64 Graphical LCD
display with backlight. The
magnitudes of the signal
peaks are indicated with a
bar graph which gets
cleared after 2 seconds.
A line marker is then left
behind to continuously
indicate the signal peak�s
magnitude until it is reset
upon the arrival of a new
signal peak.

Gain: Better than 120 dB


Low Impedance Head-
phones (4 Ohms)

200 x 110 x 90mm

1.4 kg. (Including Batteries)

2x 9 V - PP3 batteries. Accessible from the side
panel. Battery life:
Approximately 10 hours
of continuous operation.
.
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APPLICATION