2260-005 - Silicon Designs, Inc.

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] Apr 07

ORDERING INFORMATION

Full Scale

Acceleration

Model

Number

± 2 g 2260-002

± 5 g 2260-005

± 10 g 2260-010

± 25 g 2260-025

± 50 g 2260-050

±100 g 2260-100

±200 g 2260-200

SILICON DESIGNS, INC

P-Cap

Model 2260

ANALOG ACCELEROMETER MODULE

! Accurate, Easy-to-Use Alternative to

Piezoresistive Accelerometers

! Capacitive Micromachined

! Nitrogen Damped

! ±4V Differential Output or

0.5V to 4.5V Single Ended Output

! Fully Calibrated

! Low Power Consumption

! -55 to +85E

EC Operation

! +8 to +32V DC Power

! Simple Four Wire Connection

! Low Impedance Outputs Will Drive

Up To 15 Meters of Cable

! Responds to DC and AC Acceleration

! Non Standard g Ranges Available

! Rugged Anodized Aluminum Module

! Low Noise

! Serialized for Traceability

DESCRIPTION

The P-Cap

model 2260 accelerometer 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 anodized aluminum case is epoxy sealed 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 thermal gradients. The cable’s shield is electrically connected to

the case while the ground (GND) wire is isolated from the case. An optional initial calibration sheet (2260-CAL) and

periodic calibration checking are also available.

OPERATION

The P-Cap

Model 2260 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 +8 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

P-Cap is a trademark of Silicon Designs, Inc.

SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE

P-cap

IS A REGISTERED TRADEMARK OF SILICON DESIGNS, INC.

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] Apr 07

P-Cap

Model 2260 Analog Accelerometer Module

SIGNAL DESCRIPTIONS

Vs and GND (Power): Red and Black wires respectively. Power

(+9 to +32 Volts DC) and ground.

AOP and AON (Output): Green and White wires respectively.

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 two outputs can be used differentially. (See

output response plot below)

PERFORMANCE - By Model:

=+8 to +32VDC, T

=25EC

MODEL NUMBER

2260-002 2260-005 2260-010 2260-025 2260-050 2260-100 2260-200

UNITS

Input Range ±2 ±5 ±10 ±25 ±50 ±100 ±200 g

Frequency Response (Nominal, 3 dB)

0 - 400 0 - 600 0 - 1000 0 - 1500 0 - 2000 0 - 2500 0 - 2500 Hz

Sensitivity, Differential

2000 800 400 160 80 40 20 mV/g

Output Noise, Differential (RMS, typical) 13 32 63 158 316 632 1265 µg/(root Hz)

Max. Mechanical Shock (0.1 ms) 2000 g

Note 1: 250Hz ±100Hz, -3dB bandwidth, optionally available. Note 2: Single ended sensitivity is half of values shown.

PERFORMANCE - All Models:

Unless otherwise specified, Vs=+8 to +32VDC, T

=25EC, Differential Mode.

PARAMETER MIN TYP MAX UNITS

Cross Axis Sensitivity 2 3 %

Bias Calibration Error -002 2 4 % of span

-005 thru -200 2 3

Bias Temperature Shift

= -40 to +80EC)

-002 & -005 100 300 (ppm of span)/EC

-010 thru -200 50 200

Scale Factor Calibration Error

2 3 %

Scale Factor Temperature Shift (T

= -40 to +80EC) -250 +250 ppm/EC

Non-Linearity

(-90 to +90% of Full Scale)

3, 4

-002 thru -050 0.15 0.5

% of span-100 0.25 1.0

-200 0.40 1.5

Power Supply Rejection Ratio 50 >65 dB

Output Impedance 1 Ω

Output Common Mode Voltage 2.5 VDC

Operating Voltage 8 32 VDC

Operating Current (AOP & AON open) 9 12 mA DC

Mass (not including cable) 6 grams

Cable Mass 14 grams/meter

Note 3: 100g versions and above are tested from -65g to +65g. Note 4: Tighter tolerances available upon request.

SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE

P-cap

IS A REGISTERED TRADEMARK OF SILICON DESIGNS, INC.

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] Apr 07

fR C

2 1

P-Cap

Model 2260 Analog Accelerometer Module

CABLE SPECIFICATIONS & LENGTH CONSIDERATIONS

The cable consists of four 28 AWG (7x36) silver plated copper wires with PTFE insulation surrounded by a braided shield. The

shield jacket is a PTFE tape wrap with a nominal outer diameter of 0.096”. Cable lengths of up to 15 meters (50 feet) can be

added to the model 2260's standard 1 meter cable without the need to test for output instability. For lengths longer than 15

meters 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 2260 is capable of driving over 600 meters (2000

feet) of its cable type but at some length between 15 and 600 meters, each device will likely begin to exhibit oscillation.

CONVERTING THE 2260's DIFFERENTIAL OUTPUT TO SINGLE ENDED

C1 = C2 (See below for value calculation)

R1, R2, R3 & R4 = 20kΩ to 50kΩ

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 2260 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

2260 while using a single ended type connection.

This circuit converts the ± 4 Volt differential output of the model 2260 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

= R

, R

= R

and C

= C

. The gain of the circuit is then determined by the ratio R

When R

= R

, 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

= R

= 5/4 = 1.25. The single ended output of the op-amp will be

centered at ground if R

and C

are tied to ground; using some other fixed voltage for this reference will shift the output.

The value of the optional capacitors C

and C

= C

) can be selected to roll off the frequency response to the frequency

range of interest. The cutoff frequency f

(-3 dB frequency) for this single order low pass filter is given by: