I-AMP GPT 60-IV User Manual page 8

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
14 Strands of 0.2mm ø
20 Strands of 0.18mm ø
24 Strands of 0.2mm ø
32 Strands of 0.2mm ø
30 Strands of 0.25mm ø
40 Strands of 0.25mm ø
50 Strands of 0.25mm ø
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 .
INDUCTION LOOP AMPLIFIER
-AMP
EXAMPLE LOOP LENGTH = (2 X 12M) + (2 X 25M)
+ CONNECTION TO EQUIPMENT RACK (10M)
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.
~ 8 ~
G p t 6 0 - I v
Cross-sectional Approximate Ohms
Area per 100m
2
0.44 mm 4.2
0.51 mm 2 3.3
0.75 mm 2 2.1
1.00 mm 2 1.85
1.50 mm 2 1.14
2.00 mm 2 0.83
2.50 mm 2 0.65
CURRENT OUT (+)
GPT 60-IV
CURRENT OUT (-)
= 84 METRES
Approximate Cable
Ohms per Current
meter Rating
Guide
0.042 3
0.033 4
0.021 5
0.0185 6
0.0114 9
0.0083 11
0.0065 15
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