SX150DN [SENSORTECHNICS]
Pressure sensors; 压力传感器
| 型号： | SX150DN |
| 厂家： | 
SENSORTECHNICS GMBH |
| 描述： | Pressure sensors |
| 文件： | 总10页 (文件大小：253K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
SX Series
Pressure sensors
FEATURES
GENERAL DESCRIPTION
· 0...1 to 0...150 psi
The SX series of pressure sensors
provides the most cost effective
method of measuring pressures up
to 150 psi. These sensors were
specifically designed to be used with
non-corrosive and non-ionic media,
such as air and dry gases. Convenient
pressure ranges are available to
measure differential, gage and
absolute pressures from 0 to 1 psi up
to 0 to 150 psi.
· Absolute, differential
and gage devices
· High impedance bridge
· Low power consumption
for battery operation
The absolute (A) devices have an in-
ternal vacuum reference and an output
voltage proportional to absolute
pressure. The differential (D) devices
allow application of pressure to either
side of the diaphragm and can be
used for gage or differential pressure
measurements.
APPLICATIONS
· Industrial controls
· Pneumatic controls
· Medical instrumentation
· Barometry
can be o-ring sealed, epoxied, and/or
clamped onto a pressure fitting.
A closed bridge 4-pin SIP configuration
is provided for electrical connection to
the button or "N" package.
This product is packaged either in
SenSym's standard low cost chip
carrier "button" package, a plastic
ported "N" package or a dual inline
package (DIP). All packages are
designed for applications where the
sensing element is to be integral to
the OEM equipment. These packages
Because of its high-impedance
bridge, the SX series is ideal for
portable and low power or battery
opera-ted systems. Due to its low
noise, the SX is an excellent choice
for medical and low pressure
measurements.
EQUIVALENT CIRCUIT
Vs
ELECTRICAL CONNECTION
+
Output
Button sensor
GND 1
out + 2
-
P1
3
4
+VS
out -
Button sensor or "N" package
Vs
+Vs
+Vs
out +
+Vs
+Vs
+Vs
+Vs
out -
GND
out +
out +
1
1
1
P2
P1
P1
GND
out -
GND
out -
P2
4
4
4
vent hole
SXxxxGD2 DIP
-
SXxxxAD2
Output
The polarity indicated is for pressure applied to:
+
SXxxxD4 DIP
SX...
:
:
:
:
P1 (forward gage)
P1 (forward gage)
P2 (backward gage)
P2 (backward gage)
SX...AD2
SX...GD2
SX...DD4
DIP package
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SX Series
Pressure sensors
PRESSURE SENSOR CHARACTERISTICS
(Vs = 5.0 ± 0.01 V, tamb = 25 °C, common-mode pressure = 0 psig, pressure applied to P1 for Button, N and A2
housings, pressure applied to P2 for G2 and D4 housings)
Maximum ratings
Suppy voltage, VS
+12 VDC
Maximum pressure at any port11
150 psig
250 °C
Temperature ranges
Operating
Lead temperature (soldering 4 sec.)
-40°C to +85°C
-55°C to +125°C
Storage
Full-scale span1
Part number
Operating pressure Proof pressure8
Min.
15 mV
50 mV
75 mV
75 mV
100 mV
75 mV
Typ.
Max.
25 mV
SX01...
SX05...
SX15...
SX30...
SX100...
SX150...
0...1 psi
0...5 psi
20 psi
20 psi
30 psi
60 psi
150 psi
200 psi
20 mV
75 mV
110 mV
110 mV
150 mV
110 mV
100 mV
150 mV
150 mV
200 mV
150 mV
0...15 psi
0...30 psi
0...100 psi
0...150 psi
PERFORMANCE CHARACTERISTICS
(Vs = 5.0 ± 0.01 V, tamb = 25 °C, common-mode pressure = 0 psig, pressure applied to P1 for Button, N and A2
housings, pressure applied to P2 for G2 and D4 housings)
Characteristics
Zero pressure offset9
Min.
-35
Typ.
-20
Max.
0
Unit
mV
Temperature effects
(0 to 70 °C)4,7
Offset
±4
µV/V/°C
Span
-2550
+690
-2150
+750
±0.2
±0.5
±0.1
4.1
-1900
+810
±0.5
ppm/°C
Bridge impedance
Combined linearity and hysteresis2
Repeatability3
Long term stability of offset and span6
%FSS
mV
Input impedance
kΩ
Output impedance
4.1
Response time5
0.1
ms
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SX Series
Pressure sensors
TYPICAL PERFORMANCE CHARACTERISTICS
Specification notes:
1. Span is the algebraic difference between the output voltage at full-scale pressure and the output at zero pressure.
2. Hysteresis is the maximum output difference at any point within the operating pressure range for increasing and decreasing
pressure. Linearity is the maximum deviation of measure output at constant temperature (25°C) from "Best Straight Line"
determined by three points, offset, full scale pressure and half full scale pressure.
3. Maximum difference in output at any pressure with the operating pressure range and temperature within 0°C to +70°C after:
a) 100 temperature cycles, 0°C to +70°C
b) 1.0 million pressure cycles, 0 psi to full scale span
4. Slope of the best straight line from 0°C and 70°C. For operation outside this temperature, contact Sensortechnics for more
specific applications information.
5. Response time for a 0 to full-scale span pressure step change.
6. Long term stability over a one year period .
7. This parameter is not 100 % tested. It is guaranteed by process design and tested on a sample basis only.
8. If the proof pressure is exceeded, even momentarily, the package may leak or burst, or the pressure sensing die may fracture.
Note: The proof pressure for the forward gage of all devices in the D4-package is the specified value or 100 psi, whatever is less.
9. The zero pressure offset is 0 mV Min, 20 mV Typ and 35 mV Max for part nos. SX...G2 and SX...D4.
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SX Series
Pressure sensors
MECHANICAL AND MOUNTING CONSIDERATIONS
Button sensor element
The “N” package version of the sensor has
two (2) tubes available for pressure
connec-tion. For gage devices, pressure
should be applied to port P1. For differential
pressure applications, port P1 should be
used as the high pressure port and P2
should be used as the low pressure port.
Vacuum
devices)
reference
(absolute
The button sensor element was designed
to allow easy interface with additional
cases and housings which then allow
pressure connection. The device can be
mounted with an o-ring, gasket, or RTV
seals on one or both sides of the device.
The device can then be glued or clamped
into a variety of fixtures and the leads can
be bent as necessary to allow for ease of
electrical connection. However, caution is
advised as repeated bending of the leads
will cause eventual breakage.
Absolute sensors have a hermetically
sealed vacuum reference chamber. The
offset voltage on these units is therefore
measured at vacuum, 0 psia. Since all
pressure is measured relative to a vacuum
reference, all changes in barometric
pressure or changes in altitude will cause
changes in the device output.
GENERAL DISCUSSION
Output characteristics
The SX series devices give a voltage output
which is directly proportional to applied
pressure. The devices will give an increase
in positive going output when increasing
pressure is applied to pressure port P1 of
the device. If the devices are operated in
the backward gage mode, the output will
increase with decreases in pressure. The
devices are ratiometric to the supply
voltage. Changes in supply voltage will
cause proportional changes in the offset
voltage and full-scale span.
Media compatibility
SX devices are compatible with most non-
corrosive gases. Because the circuitry is
coated with a protective silicon gel, some
otherwise corrosive environments can be
compatible with the sensors. As shown in
the physical construction diagram below
for the button sensor element and ,,N”
package, fluids must generally be
compatible with silicon gel, RTV, plastic, and
aluminum for forward gage use and RTV,
silicon, glass and aluminum for backward
gage or differential applications. For
questions concerning media compatibility,
contact the factory.
For most gage applications, pressure
should be applied to the top side of the
device (see Physical Construction
Drawing). For differential applications, the
top side of the device (P1) should be used
as the high pressure port and the bottom
(P2) as the low pressure port.
The button SX package has a very small
internal volume of 0.06 cubic centimeters
for P1 and 0.001 cubic centimeters for P2.
User calibration
SX series devices feature the button IC
pressure sensor element. This will keep
overall system costs down by allowing the
user to select calibration and temperature
compensation circuits which specifically
match individual application needs. In most
cases, the primary signal conditioning
elements to be added to the SX by the user
are: offset and span calibration and
temperature compensation.
“N” packaged sensor
The "N” packaged sensor is designed for
convenient pressure connection and easy
PC board mounting. To mount the device
horizontally to a PC board, the leads can be
bent downward and the package attached
to the board using either tie wraps or
mounting
screws.
For
pressure
attachment, tygon or silicon tubing is
recommended.
Some typical circuits are shown in the
application section.
PHYSICAL CONSTRUCTION
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SX Series
Pressure sensors
APPLICATION INFORMATION
it can be seen that the sensitivity change
with temperature is slightly non-linear and
can be correlated very well with an equation
of the form:
This term enters into several compensation
circuit equations, particularly when the
bridge excitation is from a constant current
source.
General
The SX family of pressure sensors functions
as a Wheatstone bridge. When pressure is
applied to the device (see Figure I) the
resistors in the arms of the bridge change
by an amount ∆.
2
S = S [(1 - ßT ) + ρT
]
(3)
To summarize, the following list indicates
how the sensor variables can be accommo-
dated
• Full-scale span from device to device.
Make the gain adjustment in the op amp
circuitry
• Temperature coefficient of span:
1) temperature compensate the bridge or
2) temperature compensate the op amp
gain
O
D
D
where T is the temperature difference
D
between 25°C and the temperature of inte-
rest, S is the sensitivity at 25°C, and beta
O
(ß) and rho (ρ) are correlation constants.
Fortunately, between 0°C and 70°C the
change in sensitivity with temperature is
quite linear, and excellent results can be
obtained over this temperature range by
ignoring the second-order temperature
dependent term. Operating outside the 0°C
and 70°C temperature range will require a
more rigorous mathematical approach and
the use of non-linear compensating cir-
cuitry, if accuracy of better than ±1 % is re-
quired. Because the majority of SX appli-
cations fall within the 0°C to 70°C operating
temperature range, the discussion and
circuit designs given here will ignore the
non-linear effects.
• Offset voltage:
Adjustment in op amp circuitry
• Offset voltage temperature coefficient:
Usually can be ignored. For more precise
design requirements, contact the factory
for information on how to compensate for
this term.
Figure I. Button sensor bridge
schematic
The resulting differential output voltage V
0
is easily shown to be V = V x ∆. Since
the change in resistance is directly pro-
portional to pressure, V can be written as:
Bridge compensation circuits
O
B
Although thermistors can be used to tempe-
rature compensate the bridge (and in fact
will be required for extended temperature
operation), they are inherently non-linear,
difficult to use in volume production, and
more expensive than the circuit approaches
shown here, which use inexpensive semi-
conductor devices The circuits shown have
been designed to incorporate a minimum
number of adjustments and allow inter-
changeability of devices with little variation
from device to device. In general, equations
for the bridge voltage and its change with
temperature are given to enable the user to
modify or adjust the circuitry as required.
O
Thus:
V
= S x P x V ± V
OS
(1)
O
B
S = S (1 - ßT )
(4)
O
D
Where: V is the output voltage in mV
O
Substituting equation (4) into equation (1)
S is the sensitivity in mV/V per psi
P is the pressure in psi
and ignoring V , it can be shown that the
OS
necessary bridge voltage, V , will be of the
B
V
is the bridge voltage in volts.
B
form:
V
is the offset error (the differential output
2
OS
V
(1-ßT
BO
V
=V
D)
[(1 - ßT + (ßT ) +...)]
B =
BO
D
D
voltage when the applied pressure is zero).
The offset voltage presents little problem in
most applications, since it can easily be
corrected for in the amplifier circuitry, or
corrected digitally if a microprocessor is
used in the system.
where V
is the bridge voltage at 25°C.
BO
This equation is again non-linear.
However, for the temperature range of
interest, and since ß is small (0.215%/°C
from the electrical tables), the above
expression can be approximated by:
1. Diode string (Figure II)
Temperature effects
For systems using 6 V supplies, this method
of compensating for the effects of span over
temperature is the lowest cost solution The
diodes are small signal silicon diodes, such
as 1N914 or 1N4148, and do not have to
be matched.
In this discussion, for simplicity of notation,
the change of a variable with temperature
will be designated with a dot (•) over the
variable. For example,
V =V
[1 +ßT ]
D
B
BO
with less than 1 % error. Thus to compen-
sate for a negative 2150 ppm/°C sensitivity
change with temperature, the bridge voltage
should increase with temperature at a rate
of +2150 ppm/°C.
The above value of bridge voltage change
will be used in the circuit discussions that
follow. That is to say, the required change
in terms of ppm/°C is:
•
change in sensitivity
change in temperature
δS
δT
S=
=
From equation (1), and ignoring the V
OS
term, it in seen that for a given constant
pressure, the output voltage change, as a
function of temperature*, is:
•
V
B
•
V
•
= +2050 ppm/°C
(VB)
= SPV
(2)
O
B
The bridge input resistance*, R also
B
Thus, in order for output voltage to be inde-
pendent of temperature, the voltage across
the bridge, V , must change with tempera-
ture in the "opposite direction” from the
sensitivity change with temperature. From
the typical curves for the temperature
changes with temperature and is quite linear
in the temperature range of interest. The
bridge resistance has a temperature
coefficient of typically:
B
•
R
B
= +750 ppm/°C
dependence of span (span = S x P x V ),
(RB)
B
Figure II. Diode String Span
Compensation
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SX Series
Pressure sensors
APPLICATION INFORMATION (cont.)
a) V =V -4φ
a)
b)
c)
d)
V
=
α (V + I R )
B
S
B
S
O 2
a) V = V - α φ
B
S
•
φ
•
•
φ
•
•
V
φ
( )
V
R
I
V
S
B
α
( )
B
B
B
O
1-α
b)
c)
V
=
(1 - α)+
B
( ) x
b) (VB)
=
-
V
(RB)
( IO)[ ( VB )]
φ
S
( )
V
=
(VB)
V
S
- α
-4
φ
( )
φ
R
+ R
B
R
R
B
1
2
α
=
•
c) α
=
1
+
R
2
φ
= -2500 ppm/°C for silicon diodes
•
φ
( )
φ
•
•
d)
=
-2500 ppm/°C
I
R
= 3360 ppm/°C,
=+750ppm/°C
B
O
( )
φ
Figure II. Equations
(RB)
(IO)
Table I. Selected R values vs V for
S
For example, solving equation (b) for V /
B
figure III
V
when
67.7 mV
B
e)
I
O =
R
V
R
(Ω)
R (Ω)
2
1.43k
806
604
1
S
1
V
= 6.0 V
S
5V
9V
12V
3.32k
4.02k
4.22k
The design steps are straight forward:
φ
= 0.7 V
1) Knowing V and the desired bridge
S
Yields:
voltage V , solve equation (b) for α.
B
•
V
V
= 2188 ppm/°C
2) Now, solve equation (c) for R ,
2
3. Constant current excitation
(Figure IV)
B
B
letting R = 4650Ω.
B
Since the sensor’s span changes with tem-
perature at -2150 ppm/°C, this technique will
typically result in an overall negative TC of
38 ppm/C. This error is acceptable in most
applications.
3) Solve equation (a) for I
4) Find R or its nearest 1% tolerance
.
The circuits shown in Figures II and III,
although simple and inexpensive, have one
drawback in that the voltage across the
bridge is determined by the compensation
network. That is, the compensation network
is determined and what voltage is “leftover"
is across the bridge. The circuit of Figure
IV solves this problem and allows the bridge
voltage to be independently selected. In
Figure IV, the bridge is driven from a
constant current source, the LM334, which
has a very well known and repeatable
O
1
value from equation (e).
Table II gives specific 1% resistor values in
ohms, for several popular system voltages.
For best results, the resistors should be 1%
metal film with a low temperature coefficient.
For operation with V above 6V, it is recom-
S
mended to use the transistor or constant
current compensation technique.
Table II. Selected R values vs V for
S
figure IV
2. Transistor compensation network
Figure III uses a single transistor to simulate
a diode string, with the equations as shown.
The values shown in Table I were found to
give excellent results over 0°C to 70°C.
Again, if precision temperature compen-
sation is required for each device, the fixed
value resistors shown for R1 in Table I can
be replaced by a 3.24k resistor in series with
a 1k pot. Then, each devices temperature
compensation can be individually adjusted.
V
V
R (Ω)
R (Ω)
°
S
5V
B
1
2
temperature coefficient of +3300 ppm/ C.
3V
147
11.0k
9.53k
9.53k
8.25k
9.53k
This temperature coefficient (TC), in
conjunction with the TC of the bridge resis-
tance, is too high to compensate the
sensitivity TC, hence resistor R is added
to reduce the total circuit TC.
The basic design steps for this method
of temperature compensation are shown
below. However, please refer to SenSym’s
Application Note SSAN-16 for details on the
temperature compensation technique.
6V
4V
105
9V
6V
68.1
43.2
41.2
2
12V
15V
9V
10V
Amplifier design
There are hundreds of instrumentation
amplifier designs, and the intent here will
be to briefly describe one circuit which:
•
•
•
does not load the bridge
involves minimal components
provides excellent performance
Amplifier adjustment procedure
1. Without pressure applied,
(a) Short points A and B together as
shown in Figure V. Adjust the 1 k
common-mode rejection ( C M R R )
pot until the voltage at test point (T )
p
V
is equal to the voltage at test
x
point (T ) V .
p
R
This is easily accomplished by
placing a digital voltmeter between
these test points and adjusting for
0.000.
Figure IV. Constant current span TC
Compensation
Figure III. Transistor/Resistor
span TC compensation
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SX Series
Pressure sensors
APPLICATION INFORMATION (cont.)
(b) Remove the short and adjust the
The choice of the operational amplifiers to
For more precise applications amplifiers
such as the LT1014 and LT1002 have been
found to be excellent.
500 Ω offset adjust pot until V is
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.
x
again equal to V .
R
(c) Adjust the 2k reference (V ) adjust
R
pot to get an output voltage (V )
O
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.
equal to 1.00V.
2. Apply the fuII-scale pressure and adjust
the span adjust pot, R , to get the output
5
voltage that is desired to represent full-
scale.
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.
Table III. For 0 to 70°C operation
SPAN
V
5V
6V
V
R
R
FS
3V
4V
5V
5V
10V
5V
10V
R
R
p
S
B
2
1
5
3.5V
4.5V
7V
9.09k
8.45k
7.87k
7.15k
7.15k
7.68k
8.87k
118Ω
86.6Ω
54.9Ω
36.5Ω
36.5Ω
31.6Ω
31.6Ω
604Ω
604Ω
1k
1.82k
511Ω
1.4k
2k
2k
2k
5k
2k
5k
2k
9V
12V
12V
15V
15V
10V
10V
12V
12V
604Ω
Note: Application information shown here is based on the closed bridge configuration.
A =
B =
LT1014CN
LM10CN
VO = 4 [1 + 10k ] VIN + VR
RG
Resistors labled R3 are 5-Element Resistor Arrays 10 kΩ. Two required
Figure V: Button Sensor Amplifier Circuit
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SX Series
Pressure sensors
PHYSICAL DIMENSIONS
Button package
mass: 1 g
dimensions in inches (mm)
N package
mass: 5 g
dimensions in inches (mm)
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SX Series
Pressure sensors
PHYSICAL DIMENSIONS
Basic sensor DIP "D2" package
mass: 1 g
dimensions in inches (mm)
Basic sensor DIP "D4" package
0.550
(13.97)
P1
P2
0.470
(11.94)
0.050
typ.
(1.27)
0.090 typ.
(2.29)
0.300
(7.62)
0.135
(3.43)
0.380
(9.65)
0.250
(6.35)
0.285
(7.24)
0.110 typ.
(2.79)
0.070
(1.78)
0.020 typ.
(0.51)
0.01
(0.25)
0.600
(15.24)
0.100 typ.
(2.54)
mass: 1 g
dimensions in inches (mm)
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SX Series
Pressure sensors
ORDERING INFORMATION
Order part no.
DIP "D2" package
Pressure range
DIP "D4" package
(dual ported)
Button package
"N" package
(single ported)
0 - 15 psi
SX15A
SX30A
SX15AN
SX30AN
SX100AN
---
SX15AD2
---
0 - 30 psi
0 - 100 psi
0 - 150 psi
0 - 1 psi
SX30AD2
---
Absolute
pressure
SX100A
SX150A
SX100AD2
---
---
---
SX01GD2
---
0 - 5 psi
SX05GD2
---
---
use
differential
devices
use
differential
devices
0 - 15 psi
0 - 30 psi
0 - 100 psi
0 - 150 psi
0 - 1 psi
SX15GD2
Gage
pressure
SX30GD2
---
SX100GD2
---
---
---
---
---
---
---
---
---
SX01D
SX05D
SX15D
SX30D
SX100D
SX150D
SX01DN
SX05DN
SX15DN
SX30DN
SX100DN
SX150DN
SX01DD4
SX05DD4
SX15DD4
SX30DD4
SX100DD4
---
0 - 5 psi
0 - 15 psi
0 - 30 psi
0 - 100 psi
0 - 150 psi
Differential
pressure
SenSym and Sensortechnics reserve the right to make changes to any products herein. SenSym and Sensortechnics do not assume any
liability arising out of the application or use of any product or circuit described herein, neither does it convey any license under its patent
rights nor the rights of others.
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