SILICON DESIGNS, INC P-CapTM 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 ORDERING INFORMATION Full Scale Acceleration Model Number ± 2g ± 5g ± 10 g ± 25 g ± 50 g ±100 g ±200 g 2260-002 2260-005 2260-010 2260-025 2260-050 2260-100 2260-200 DESCRIPTION The P-CapTM 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-CapTM 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. 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 P-CapTM 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: VS=+8 to +32VDC, TC=25EC MODEL NUMBER Frequency Response (Nominal, 3 dB) Sensitivity, Differential UNITS 2260-002 2260-005 2260-010 2260-025 2260-050 2260-100 2260-200 Input Range 1 ±2 ±5 0 - 400 0 - 600 2000 13 800 32 2 Output Noise, Differential (RMS, typical) ±10 ±25 ±50 ±100 ±200 0 - 1000 0 - 1500 0 - 2000 0 - 2500 0 - 2500 400 63 160 158 80 316 40 632 20 1265 2000 Max. Mechanical Shock (0.1 ms) Note 1: 250Hz ±100Hz, -3dB bandwidth, optionally available. g Hz mV/g µg/(root Hz) g Note 2: Single ended sensitivity is half of values shown. PERFORMANCE - All Models: Unless otherwise specified, Vs=+8 to +32VDC, TC=25EC, Differential Mode. PARAMETER MIN Cross Axis Sensitivity -002 -005 thru -200 -002 & -005 -010 thru -200 Bias Calibration Error Bias Temperature Shift (TC= -40 to +80EC) Scale Factor Calibration Error 3 Scale Factor Temperature Shift (TC= -40 to +80EC) Non-Linearity (-90 to +90% of Full Scale) 3, 4 MAX UNITS 2 2 2 100 50 3 4 3 300 200 % 2 3 +250 % ppm/EC 0.15 0.25 0.40 >65 1 2.5 0.5 1.0 1.5 % of span -250 -002 thru -050 -100 -200 Power Supply Rejection Ratio Output Impedance Output Common Mode Voltage Operating Voltage TYP 50 8 32 12 % of span (ppm of span)/EC dB Ω VDC VDC mA DC Operating Current (AOP & AON open) 9 Mass (not including cable) Cable Mass 6 grams 14 grams/meter Note 3: 100g versions and above are tested from -65g to +65g. SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE Note 4: Tighter tolerances available upon request. 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-CapTM 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 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 = SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE 1 2π R2 C1 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