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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: VS=+9 to +32VDC, TC=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 g/(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, TC=25EC, Differential Mode.
PARAMETER Cross Axis Sensitivity Bias Calibration Error Bias Temperature Shift (TC= -40 to +80EC) Scale Factor Calibration Error Scale Factor Temperature Shift (TC= -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 A741 or 1/4 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 R1 = R3, R2 = R4 and C1 = C2. The gain of the circuit is then determined by the ratio R2/R1. When R1 = R2 = R3 = R4, 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 R2/R1 = R4/R3 = 5/4 = 1.25. The single ended output of the op-amp will be centered at ground if R2 and C1 are tied to ground; using some other fixed voltage for this reference will shift the output. The value of the optional capacitors C1 and C2 (C1 = C2) can be selected to roll off the frequency response to the frequency range of interest. The cutoff frequency f0 (-3 dB frequency) for this single order low pass filter is given by:
f0 =
1 2 R2 C1
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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