SX Series
Pressure sensors
APPLICATION INFORMATION (cont.)
(b) Remove the short and adjust the
500
Ω
offset adjust pot until Vx is
again equal to VR.
(c) Adjust the 2k reference (VR) adjust
pot to get an output voltage (VO)
equal to 1.00V.
2. Apply the fuII-scale pressure and adjust
the span adjust pot, R5, to get the output
voltage that is desired to represent full-
scale.
Table III. For 0 to 70°C operation
SPAN
FS
3V
4V
5V
5V
10V
5V
10V
The choice of the operational amplifiers to
use is based on individual cost/performance
trade-offs. The accuracy will be primarily
limited by the amplifier’s common-mode
rejection, offset voltage drift with tempera-
ture and noise performance. Low cost, low
performance devices, such as the LM324
can be used if the temperature ranges
limited to 25°C +15°C and an accuracy of
+2% is adequate.
For more precise applications amplifiers
such as the LT1014 and LT1002 have been
found to be excellent.
An amplifier that uses a single supply is
shown in Figure V. Table III gives resistor
values for various supply and full-scale
output combinations.
Factory compensated devices
This application note provides the neces-
sary information for temperature compen-
sating and calibrating the SX sensors. In
some case, the customer may find that SX
devices which have been factory adjusted
for temperature compensation and span are
more economical for a particular application.
SenSym does offer devices with this feature.
For more information on these factory
calibrated and compensated devices, the
SCX series and SDX series, please contact
Sensortechnics.
VS
5V
6V
9V
12V
12V
15V
15V
VB
3.5V
4.5V
7V
10V
10V
12V
12V
R2
9.09k
8.45k
7.87k
7.15k
7.15k
7.68k
8.87k
R1
118Ω
86.6Ω
54.9Ω
36.5Ω
36.5Ω
31.6Ω
31.6Ω
R5
604Ω
604Ω
1k
1.82k
511Ω
1.4k
604Ω
Rp
2k
2k
2k
5k
2k
5k
2k
Note:
Application information shown here is based on the closed bridge configuration.
A=
B=
LT1014CN
LM10CN
V
O
= 4
[
1 +
10k
R
G
]
V
IN
+ V
R
Resistors labled R
3
are 5-Element Resistor Arrays 10 kΩ. Two required
Figure V: Button Sensor Amplifier Circuit
July 2008 / 052
7/10
www.sensortechnics.com
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