Datasheet

SBOA102A
January 2005
Sensor-Emulator-EVM
System Reference Guide
9
This is a simplified diagram of how the sensor emulator
generates a bridge output voltage. The potentiometer
R102 is adjusted to set the output voltage of the
emulated bridge (V
in+
with respect to V
in-
). The
potentiometer R103 is used to make fine adjustments in
the output value. R8 and R9 set a common mode
voltage for the other leg of the bridge. R101 and R104
set the adjustable output range of the emulated bridge.
For the configuration shown, the output range is -25mV
to +26mV (V
dif
= V
in-
-V
in+
). Selecting a different value
for R101 and R104 can expand this range. On the
Sensor-Emulator-EVM, 11 channels like this one are
selectable using a rotary switch.
Figure 2.5
10k
10k
10k
10k
Output of Sensor
Vin+ to Signal
Conditioning Chip
Output of Sensor
Vin-to Signal
Conditioning Chip
Input To Bridge
Vexc
(Excitation voltage)
200 ohm
10 ohm
V
dif
=
26mV
-25mV
to
2.526V
Wiper at top
2.475V
Wiper at bottom
to
2.5V
5.0V
R8
R9 R104
R103
R102
R101
2.5V
Emulating
Bridge Sensor Outputs
Positive full scale of the emulator
V
exc
5:= R
104
1010
3
⋅:= R
102
200:= R
101
1010
3
⋅:=
R
102a
200:=
Wiper position at top of POT
R
103
10:=
Pot set to maximum Resistance
V
dif
V
exc
R
104
R
103
+ R
102a
+
( )
⋅
R
101
R
104
+ R
103
+ R
102
+
V
exc
2
−:=
V
dif
0.026=
Positive full scale output of emulator
Negative full scale of the emulator
V
exc
5:= R
104
1010
3
⋅:= R
102
200:= R
101
1010
3
⋅:=
R
102a
0:=
Wiper position at bottom of POT
R
103
0:=
Pot set to Minimum Resistance
V
dif
V
exc
R
104
R
103
+ R
102a
+
( )
⋅
R
101
R
104
+ R
103
+ R
102
+
V
exc
2
−:=
V
dif
0.025−=
Negative full scale output of emulator