Datasheet
LTC2410
36
APPLICATIO S I FOR ATIO
WUU
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BRIDGE APPLICATIONS
Typical strain gauge based bridges deliver only 2mV/Volt
of excitation. As the maximum reference voltage of the
LTC2410 is 5V, remote sensing of applied excitation
without additional circuitry requires that excitation be
limited to 5V. This gives only 10mV full scale input signal,
which can be resolved to 1 part in 10000 without averag-
ing. For many solid state sensors, this is still better than
the sensor. Averaging 64 samples however reduces the
noise level by a factor of eight, bringing the resolving
power to 1 part in 80000, comparable to better weighing
systems. Hysteresis and creep effects in the load cells are
typically much greater than this. Most applications that
require strain measurements to this level of accuracy are
measuring slowly changing phenomena, hence the time
required to average a large number of readings is usually
not an issue. For those systems that require accurate
measurement of a small incremental change on a signifi-
cant tare weight, the lack of history effects in the LTC2400
family is of great benefit.
For those applications that cannot be fulfilled by the
LTC2410 alone, compensating for error in external ampli-
fication can be done effectively due to the “no latency”
feature of the LTC2410. No latency operation allows
samples of the amplifier offset and gain to be interleaved
with weighing measurements. The use of correlated double
sampling allows suppression of 1/f noise, offset and
thermocouple effects within the bridge. Correlated double
sampling involves alternating the polarity of excitation and
dealing with the reversal of input polarity mathematically.
Alternatively, bridge excitation can be increased to as
much as ±10V, if one of several precision attenuation
Figure 46. Using Multiple LTC2410s to Increase Output Data Rate
CS1
CS2
CS3
2410 F46
CS4
SCK
31 OR LESS
CLOCK PULSES
SDO
LTC2410
#1
SCK
SDO
CS1
CS2
CS3
CS4
LTC2410
#2
LTC2410
#3
LTC2410
#4
µCONTROLLER
EXTERNAL OSCILLATOR
(153,600HZ)
V
REF
+
V
REF
–
V
CC
REF
+
REF
–
IN
+
IN
–
GND
F
O
SCK
SDO
CS
V
CC
REF
+
REF
–
IN
+
IN
–
GND
F
O
SCK
SDO
CS
V
CC
REF
+
REF
–
IN
+
IN
–
GND
F
O
SCK
SDO
CS
V
CC
REF
+
REF
–
IN
+
IN
–
GND
F
O
SCK
SDO
CS