Datasheet

LTC2410
40
APPLICATIO S I FOR ATIO
WUU
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The error associated with the 10V excitation would be
–80ppm. Hence, overall reference error could be as high
as 130ppm, the average of the two.
Figure 53 shows a similar scheme to provide excitation
using resistor arrays to produce precise gain. The circuit
is configured to provide 10V and –5V excitation to the
bridge, producing a common mode voltage at the input to
the LTC2410 of 2.5V, maximizing the AC input range for
applications where induced 60Hz could reach amplitudes
up to 2V
RMS
.
The last two example circuits could be used where mul-
tiple bridge circuits are involved and bridge output can be
multiplexed onto a single LTC2410, via an inexpensive
multiplexer such as the 74HC4052.
Figure 54 shows the use of an LTC2410 with a differential
multiplexer. This is an inexpensive multiplexer that will
contribute some error due to leakage if used directly with
the output from the bridge, or if resistors are inserted as
a protection mechanism from overvoltage. Although the
bridge output may be within the input range of the A/D and
multiplexer in normal operation, some thought should be
given to fault conditions that could result in full excitation
voltage at the inputs to the multiplexer or ADC. The use of
amplification prior to the multiplexer will largely eliminate
errors associated with channel leakage developing error
voltages in the source impedance.
Figure 51. Remote Half Bridge Sensing with Noise Suppression on Reference
Figure 50. Remote Half Bridge Interface
2410 F50
REF
+
REF
–
IN
+
IN
–
GND
V
CC
V
S
2.7V TO 5.5V
3
4
5
6
PLATINUM
100Ω
RTD
R1
25.5k
0.1%
1, 7, 8, 9,
10, 15, 16
2
LTC2410
REF
+
REF
–
IN
–
GND
V
CC
5V
3
4
6
2410 F51
1, 7, 8, 9,
10, 15, 16
2
LTC2410
–
+
LTC1050
5V
PLATINUM
100Ω
RTD
560Ω
R3
10k
5%
R1
10k, 5%
R2
10k
0.1%
1µF
IN
+
5
10k
10k