I-AMP GPT 60-IV User Manual - page 8
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Excellence Through Engineering
The Venue Master field strength meter (part of the I-AMP range of products) has been designed to allow full
frequency response measurement of a induction loop system, allowing compensation of metal loss.
SELECTION OF THE INDUCTION LOOP CABLE
The selection of the Induction loop cable is based on a minimum required induction loop resistance at DC of
0 Ohms and a maximum of 1.8 Ohms. The following guide indicates typical wire gauges and their
associated DC resistance:
Typical Conductor
Stranding
Cross-sectional
Area
Approximate Ohms
per 100m
Approximate
Ohms per
meter
Cable
Current
Rating
Guide
14 Strands of 0.2mm ø
0.44 mm
2
4.2
0.042
3
20 Strands of 0.18mm ø
0.51 mm
2
3.3
0.033
4
24 Strands of 0.2mm ø
0.75 mm
2
2.1
0.021
5
32 Strands of 0.2mm ø
1.00 mm
2
1.85
0.0185
6
30 Strands of 0.25mm ø
1.50 mm
2
1.14
0.0114
9
40 Strands of 0.25mm ø
2.00 mm
2
0.83
0.0083
11
50 Strands of 0.25mm ø
2.50 mm
2
0.65
0.0065
15
Cable Selection Step 1:Calculate the length of the induction loop required to cover the pick-up area
selected. Allow for the connection to and from the GPT 60-IV .
-AMP
GPT 60-IV
CURRENT OUT (+)
CURRENT OUT (-)
INDUCTION LOOP AMPLIFIER
EXAMPLE LOOP LENGTH = (2 X 12M) + (2 X 25M)
+ CONNECTION TO EQUIPMENT RACK (10M)
= 84 METRES
Cable Selection Step 2:Multiply the loop length by each of the ohms/per meter values shown in the table
above. Select the cable that gives a total loop resistance between 0 and 1.8 Ohms.