SILICON DESIGNS, INC
!
Hermetically Sealed Titanium Case
!
Detachable Cable (sold separately)
!
Capacitive Micromachined
!
Nitrogen Damped
!
±4V Differential Output or
0.5V to 4.5V Single Ended Output
!
Fully Calibrated
!
Low Power Consumption
!
-55 to +125EC Operation
E
!
+9 to +32V DC Power
!
Simple Four Wire Connection
!
Low Impedance Outputs Will Drive
Up To 50 Feet of Cable
!
Responds to DC and AC Acceleration
!
Non Standard g Ranges Available
!
Low Noise
!
Serialized for Traceability
Model 2240
ANALOG ACCELEROMETER MODULE
ACTUAL SIZE
(CABLE SOLD SEPARATELY)
ORDERING INFORMATION
Full Scale
Acceleration
± 2g
± 5g
± 10 g
± 25 g
± 50 g
±100 g
±200 g
Accelerometer
Model
Number
2240-002
2240-005
2240-010
2240-025
2240-050
2240-100
2240-200
Cable
Length
4 ft
14 ft
33 ft
50 ft
Cable
Model
Number
2240-CAB-04
2240-CAB-14
2240-CAB-33
2240-CAB-50
DESCRIPTION
The model 2240 accelerometer is a hermetically sealed version of the model 2220. This rugged module combines
an integrated model 1221L accelerometer with high drive, low impedance buffering for measuring acceleration in
commercial/industrial environments. It is tailored for zero to medium frequency instrumentation applications. The
titanium case is sealed using a laser welding process and is easily mounted via two #4 (or M3) screws. On-board
regulation is provided to minimize the effects of supply voltage variation. It is relatively insensitive to temperature
changes and gradients. A model 2240-CAB cable, sold separately (see order information above), connects via a
miniature 4-pin screw-on connector. The cable’s shield is electrically connected to the titanium case while the ground
(GND) wire is isolated from the case. An initial calibration sheet (2240-CAL) is included and periodic calibration
checking is available.
OPERATION
The Model 2240 accelerometer module produces two analog voltage outputs which vary with acceleration as shown
in the graph on the next page. The sensitive axis is perpendicular to the bottom of the package, with positive
acceleration defined as a force pushing on the bottom of the package. The signal outputs are fully differential about
a common mode voltage of approximately 2.5 volts. The output scale factor is independent from the supply voltage
of +9 to +32 volts. At zero acceleration the output differential voltage is nominally 0 volts DC; at ±full scale
acceleration the output differential voltage is ±4 volts DC respectively.
APPLICATIONS
!
FLIGHT TESTS
!
VIBRATION MONITORING
!
VIBRATION ANALYSIS
!
MACHINE CONTROL
!
MODAL ANALYSIS
!
ROBOTICS
!
CRASH TESTING
!
INSTRUMENTATION
Silicon Designs, Inc.
!
1445-NW Mall Street, Issaquah, WA 98027-5344
!
Phone: 425-391-8329
!
Fax: 425-391-0446
web site:
www.silicondesigns.com
[page 1]
Feb 08
Model
2240
Analog Accelerometer Module
SIGNAL DESCRIPTIONS
Vs and GND (Power):
Red and Black wires respectively for the
2240-CAB cable (ordered separately). Power (+9 to +32 Volts
DC) and ground.
AOP and AON (Output):
Green and White wires respectively for
the 2240-CAB cable (sold separately). Analog output voltages
proportional to acceleration; AOP voltage increases (AON
decreases) with positive acceleration. At zero acceleration both
outputs are nominally equal to 2.5 volts. The device experiences
positive (+1g) acceleration with its lid facing up in the Earth’s
gravitational field. Either output can be used individually or the
outputs can be used differentially. (See response plot below).
1.00 [25.4]
0.825 [20.95]
SILICON
DESIGNS
0.24 [6.1]
1/4-28,
4-PIN
CONNECTOR
1.00 [25.4]
2240-XXX
S/N XXXX
0.50 [12.7]
0.22 [5.6]
0.44 [11.2]
0.127
[3.23] DIA
Positive
Acceleration
0.15 [3.8]
(ACTUAL SIZE)
0.33 [8.4]
GND
AON
INCH [mm]
AOP
Vs
= Location of Sense Element
PERFORMANCE
- By Model:
V
S
=+9 to +32VDC, T
C
=25EC
MODEL NUMBER
Input Range
Frequency Response
(Nominal, 3 dB)
Sensitivity, Differential
2
1
2240-002 2240-005 2240-010 2240-025 2240-050 2240-100 2240-200
±2
0 - 400
2000
8
±5
0 - 600
800
9
±10
400
10
±25
160
25
2000
Note 2: Single ended sensitivity is half of values shown.
±50
80
50
±100
40
100
±200
20
200
0 - 1000 0 - 1500 0 - 2000 0 - 2500 0 - 3000
UNITS
g
Hz
mV/g
µg/(root
Hz)
g
Output Noise, Differential
(RMS, typical)
Max. Mechanical Shock
(0.1 ms)
Note 1: 250Hz ±100Hz, -3dB bandwidth, optionally available.
PERFORMANCE
- All Models:
Unless otherwise specified,
Vs=+9
to +32VDC, T
C
=25EC, Differential Mode.
PARAMETER
Cross Axis Sensitivity
Bias Calibration Error
Bias Temperature Shift
(T
C
= -40 to +80EC)
Scale Factor Calibration Error
Scale Factor Temperature Shift
(T
C
= -40 to +80EC)
Non-Linearity
(-90 to +90% of Full Scale)
3
MIN
-002
-005 thru -200
-002
-005 thru -200
-002 thru -010
-025 thru -200
-002 thru -050
-100
-200
50
-250
-150
TYP
1
MAX
2
4.0
1.5
200
100
2
+150
UNITS
%
% of span
(ppm of span)/EC
%
ppm/EC
100
50
1
3, 4
Power Supply Rejection Ratio
Output Impedance
Output Common Mode Voltage
Operating Voltage
Operating Current
(AOP & AON open)
Mass
(not including cable)
Cable Mass
Note 3: 100g versions and above are tested from -65g to +65g.
SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE
0.15
0.25
0.40
>65
1
2.45
12
10
25
0.5
1.0
1.5
% of span
dB
VDC
VDC
mA DC
grams
grams/meter
9
32
14
Note 4: Tighter tolerances are available on special order.
Silicon Designs, Inc.
!
1445-NW Mall Street, Issaquah, WA 98027-5344
!
Phone: 425-391-8329
!
Fax: 425-391-0446
web site:
www.silicondesigns.com
[page 2]
Feb 08
Model
2240
Analog Accelerometer Module
CABLE SPECIFICATIONS & LENGTH CONSIDERATIONS
The cable consists of four 30 AWG (7x38) silver plated copper wires with PTFE insulation surrounded by a braided shield. The
black FEP shield jacket has a nominal outer diameter of 0.100”. Cable lengths of up to 50 feet (15 meters) can be added to the
model 2240's standard 4 foot cable without the need to test for output instability. For lengths longer than 50 feet, we recommend
you check each individual installation for oscillation by tapping the accelerometer and watching the differential output for
oscillation in the 20kHz to 50kHz region. If no oscillation is present then the cable length being used is OK. From the standpoint
of output current drive and slew rate limitations, the model 2240 is capable of driving over 2000 feet (600 meters) of its cable type
but at some length between 50 and 2000 feet, each device will likely begin to exhibit oscillation.
CONVERTING THE 2240's DIFFERENTIAL OUTPUT TO SINGLE ENDED
C1 = C2 (See below for value calculation)
R1, R2, R3 & R4 = 20k to 50k
R1 = R3 to within 0.1% for good common mode rejection
R2 = R4 to within 0.1% for good common mode rejection
R2 / R1 ratio accurate to within 0.1% for gain control
R4 / R3 ratio accurate to within 0.1% for gain control
To achieve the highest resolution and lowest noise performance from your model 2240 accelerometer module, it should
be connected to your voltage measurement instrument in a differential configuration using both the
AOP
and
AON
output
signals. If your measurement instrument lacks differential input capability or you desire to use a differential input capable
instrument in single ended mode, then the circuit above can be used to preserve the low noise performance of the model
2240 while using a single ended type connection.
This circuit converts the ± 4 Volt differential output of the model 2240 accelerometer, centered at +2.5 Volts, to a single
ended output centered about ground (0.0 Volts). It provides the advantage of low common mode noise by preventing the
accelerometer’s ground current from causing an error in the voltage reading.
The op-amp should be located as close as possible to your voltage monitoring equipment so that the majority of the signal
path is differential. Any noise present along the differential path will affect both wires to the same degree and the op-amp
will reject this noise because it is a common mode signal. The op-amp type is not critical; a
µA741
or ¼ of a LM124 can
be used. Both plus and minus supplies are needed for the op-amp to accommodate the positive and negative swings of
the single ended output.
For this design, always set R
1
= R
3
, R
2
= R
4
and C
1
= C
2
. The gain of the circuit is then determined by the ratio R
2
/R
1
.
When R
1
= R
2
= R
3
= R
4
, the gain equals 1 and the output swing will be ± 4 Volts single ended with respect to ground. To
obtain a ± 5 Volt single ended output, set R
2
/R
1
= R
4
/R
3
= 5/4 = 1.25. The single ended output of the op-amp will be
centered at ground if R
2
and C
1
are tied to ground; using some other fixed voltage for this reference will shift the output.
The value of the optional capacitors C
1
and C
2
(C
1
= C
2
) can be selected to roll off the frequency response to the frequency
range of interest. The cutoff frequency
f
0
(-3 dB frequency) for this single order low pass filter is given by:
1
f
0
=
2
π
R
2
C
1
SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE
Silicon Designs, Inc.
!
1445-NW Mall Street, Issaquah, WA 98027-5344
!
Phone: 425-391-8329
!
Fax: 425-391-0446
web site:
www.silicondesigns.com
[page 3]
Feb 08
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