Technical Manual
Page 18
CODEL
OPS.109
Issue : B
Rev. : 1
Date : 23/10/13
Doc. i/d : 0109/6
Ref. : 090028
The table below gives the gain values represented by the dip switch settings.
Gain Switch
1
2
3
4
Gain Value
Low gain
0
0
0
0
1
1
0
0
0
2
0
1
0
0
4
1
1
0
0
5
0
0
1
0
7.7
1
0
1
0
15.4
0
1
1
0
30.8
1
1
1
0
38.5
0
0
0
1
15.7
1
0
0
1
31.4
0
1
0
1
62.8
1
1
0
1
78.5
0
0
1
1
22.4
1
0
1
1
44.8
0
1
1
1
89.6
High gain
1
1
1
1
112.0
If with a software gain setting of 0 the rms value of channel
‘A’ is greater than 80 the hardware gain must be
reduced. If the rms value of channel
‘A’ is less than 20 with a gain setting of 4 the hardware gain must be
increased.
6.6.1. Detector Levels
Transducer Gain
The instrument operates by correlating the signals received by the two optical transducers. It is important to
ensure that the signal levels from the two transducers are correct. There are two levels of gain adjustment; one
a hardware gain adjustment in the sensing heads and the other a software gain adjustment in the signal
processor.
The software gain comprises two elements:
-
an overall gain applied to both transducers with a gain factor in the range 0 to 4 that is applied
as 2
n
so that 0 is a gain of 1 and 4 is a gain of 16 and
-
a channel
‘B’ gain factor applied only to channel ‘B’.
The channel
‘B’ gain is in the range 1 to 255. This is applied as an arithmetic gain with a normalised value of 64.
A gain value of 32 will thus represent a real gain of 0.5 while a gain value of 128 represents a real gain of 2.
These software gains are normally operated in an automatic mode with the channel
‘B’ gain designed to ensure
that the rms values from the two transducers are approximately equal.