Datasheet
SBOA102A
January 2005
Sensor-Emulator-EVM
System Reference Guide
17
Figure 3.1 illustrates how the range of the bridge emulator can be adjusted by putting a resistor in parallel with R101 and R104. This needs to be
done for each channel of the emulator (11 channels x 2 resistors= 22 resistors total). The examples illustrates how the range is increased using a
1kΩ parallel resistor. In general, it is best to select a parallel resistance value that scales your range so that the full scale output of the emulator is
slightly larger than what is required for your emulator. Scaling the emulator in this manner will provide the optimal resolution and lowest noise. Note
that holes are provided for a parallel through-hole resistor to simplify the process of adjusting the emulator scale.
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−=
Positive full scale output of emulator
Figure 3.0: Default Range Figure 3.1: Adjusted Range
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
3.0 Changing the Programmable Range of the Emulator
Positive full scale of the emulator
V
exc
5:= R
104
909.1:= R
102
200:= R
101
909.1:=
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
0.259=
Positive full scale output of emulator
Negative full scale of the emulator
V
exc
5:= R
104
909.1:= R
102
200:= R
101
909.1:=
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
0.248−=
Negative full scale output of emulator