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ADVANCED COMMUNICATIONS & SENSING
The "PGA" controls should then look like the picture below.
17.6
ZoomingADC™ Configuration
17.6.1 Zooming on the Signal
As the sensor is supposed to work at the atmospheric pressure (max: 107.8kPa - min: 88.7kPa) we will zoom
on around these values and thus use the maximum amplification as possible to get the full signal at the ADC
input.
As for zoom in pictures we set a particular zone of interest called measuring window (in red below).
Sensor output Voltage vs Pressure @ 3.3V supply
16
Min
14
Typ
Max
12
10
8
6
4
2
0
-2
40
0
20
60
17.6.2 Gain Computing
To compute the total gain that must be applied to the sensor output signal we must know 2 parameters:
1. The maximum output span of the ADC, here 3.3V
2. The maximum output span value of the sensor in the measuring window, here around 8.5-4.5 = 4mV
ACS - Revision 1.0
© Semtech Corp.
Figure 37. SX8724S "PGA" Group of Controls Configuration
Measuring window
Measuring window
80
100
120
140
160
180
Pressure [kPa]
Figure 38. Zooming on the Signal
May 2011
Evaluation Kit for SX8724S Data Acquisition System
ADC input sensor voltage vs pressure
1800
Min
1600
Typ
Max
1400
1200
1000
800
600
400
200
0
89
91
200
Page 42
SX8724SEVK
97
93
95
99
101
103
Pressure [kPa]
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USER GUIDE
105
107
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