CAN-CBX-AI420 - esd electronics, Inc.
CAN-CBX-AI420 - esd electronics, Inc.
CAN-CBX-AI420 - esd electronics, Inc.
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4.2 Analogue Inputs<br />
to/from<br />
microcontroller<br />
<br />
Digital Isolator<br />
IL716<br />
Sigma-Delta A/D-Converter<br />
AD7732BRU<br />
DOUT<br />
DIN<br />
SCLK<br />
RDY#<br />
Electrical Isolation<br />
AIN0+<br />
AIN0-<br />
Description of the Units<br />
<strong>CAN</strong>-<strong>CBX</strong>-<strong>AI420</strong> Manual Rev. 1.3 19<br />
100p<br />
FE (Functional<br />
earth ground)<br />
100p<br />
FE (Functional<br />
earth ground)<br />
WE 74279207<br />
WE 74279207<br />
1P<br />
Pin 2<br />
1M<br />
Pin 3<br />
G<br />
Analog_GND<br />
Fig. 12: Analogue input circuit (example: channel 1)<br />
Principle of internal circuit of the<br />
Sigma-Delta A/D-converter<br />
AD7732BRU<br />
Converter<br />
Ref<br />
ca. 100k<br />
AIN+<br />
R SOURCE<br />
Pin 1<br />
X500<br />
Socket<br />
MC1,5/12-G-3,81-AU<br />
Attention: The internal circuit of the -converter (see figure below) and the wiring of<br />
the sensor signal cause a gain-error at the measuring. This fault is the smaller,<br />
the lower the resistance of the sensor is chosen.<br />
Furthermore the resistors of both measuring lines of the differential analogue<br />
inputs should be identical.<br />
Fig. 13: Principle of the internal circuit of the -converter<br />
The gain-error increases with increasing resistance R SOURCE (see figure above).
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