Mantracourt Electronics Limited
SGA/A & SGA/D User Manual
13
Chapter 4 Calibration
The SGA/A & SGA/D provides the excitation supply and signal conditioning to cater for a wide range of strain
gauges, load cells, pressure transducers or torque transducers.
Output
Select the analogue output range as detailed in Chapter 3, Figure 3.1,Table 3.1 & 3.2 by means of SW4.
Zero Offset
Select the offset as detailed in Chapter 3, Table 3.9 by means of SW2.
Having selected the polarity and the offset nearest to that required with the switches use the fine potentiometer P2
to achieve the final setting.
Sensitivity
Select the sensitivity as detailed in Chapter 3, Table 3.6 by means of SW1.
Switches 1-4 of SW1 provide fine setting of the SGA sensitivity while switches 5-7 give coarse control.
This arrangement allows the SGA to cover a wide range of strain gauge sensitivities without sacrificing stability and
ease of set up.
Locate the required sensitivity in the table and set switches 1-7 of SW1 accordingly.
Potentiometer P1 provides fine trimming and range overlap to enable the SGA to be calibrated precisely to any
given value within its ranges.
Note
1
If the
range
is
repeated
in
the
table
e.g.
4mV/V
(4.0,
4.05
and
4.0
mV/V)
choose the
setting which has the greatest number of switches 1-4 set to ‘off’
i.e.
SW1
=
[1000]
[000].
This
will
enable
finer
trimming
to
the
final value
using
potentiometer
PI.
The sensitivity settings shown in Table 3.6 assume that the load cell is fully loaded. The sensitivity settings can be
used to maximise the output when the full range of the load cell is not being used. Here are a couple of examples.
Example
1
A 2.5mV/V load cell provides 10V for an l00Ib load. However it is never loaded above
50lb
The sensitivity setting can be set to 1.25 mV/V.
Table
3.6
/20
(1.20mV/V
SW1
=
[1101][000]
Example
2
When
a
reduced
output
is
required
from
a
fully
loaded
transducer,
use
a
less
sensitive switch
setting.
For an 8 volt output from a fully loaded 2.5mV/V load cell use the 3.19mV/V setting
i.e. (10/8x2.5=3.125mV/V)
Table 3.6 /31 (1.20mV/V SW1 =[0010][000]
