ACCELEROMETER SPECIFICATION

Transcription

1 ACCELEROMETER SPECIFICATION Model 4384 LINEAR SERVO ACCELEROMETER MODEL 4384 LINEAR SERVO ACCELEROMETER The proven performer for flight control, autopilot, guidance, and instrumentation applications in missile, spacecraft, and aircraft systems. This highly sensitive linear servo accelerometer provides extremely accurate low-level acceleration measurement under high levels of environmental vibration and shock. Approved for general release. BEI Precision Systems & Space Company, Inc Murphy Drive # Maumelle, AR USA # Tel: # Fax: /2010 MM-046B

2 Page 2 BEI Precision Systems and Space Company's Model 4384 Linear Servo Accelerometer provides a standard product approach to meet your flight control, guidance, and instrumentation system demands. Originally developed as an advanced, ruggedized version of our Model 4310 series accelerometers, we designed the Model 4384 specifically for high-volume production. Design Benefits: Accelerometer reliability and performance are important prerequisities in order to achieve overall system goals. The Model 4384 consistently meets program requirements, featuring: Qualified and Proven Design: The Model 4384 has qualified for extensive commercial and military aerospace applications, utilizing our basic design with a proven applications history of over 50,000 accelerometers. # Rugged Design: Optional incorporation of BEI PSSC's Dynamic Range Change (DYNA-RANGE ) provides the Model 4384 with increased high-frequency g-range capability without saturation, distortion, or bias offsets-under high levels of applied vibration. The unit survives random vibration levels as high as 25g rms. # High Performance: Linearity better than 0.05% of full range. # High Accuracy/High Sensitivity: Resolution less than 0.001% of full range. # Wide Temperature Range: The Model 4384 functions accurately in temperatures ranging from -54/C to +93/C (-65/F to +200/F). In fact, the unit operates with low composite error, without heaters or other thermal environment controls. # Unsurpassed Reliability: MTBF in excess of 40,000 flight hours. # Long Life With No Maintenance: Single sensing element, with less than one milliradian motion. The total sensing system weighs less than 300 milligrams. Contains virtually no moving parts, and requires no maintenance. # Self-Test Capability: Contains built-in test (BIT), utilizing an external current source for flight control check-out and component test. # Small and Light Design: Weighs less than 85 grams (3 ounces). # High Production Capability: BEI Precision Systems & Space Company, Inc. can meet the production schedule demanded by major programs. # Quality Production Capability: The standard manufacturing, inspection, and quality control systems at BEI PSSC meet ISO 9001:2008, as well as stringent NASA requirements. Technical Design and Theory of Operation: The Model 4384 operates on the torque balance principle employed in all BEI PSSD accelerometers. We incorporated our exclusive Diamond Torsion-Bar suspension system and our patented Position Detector to design a highly accurate, extremely rugged sensor. As indicated in Figure 1, the unit consists of a lightweight vane attached to a torque generator, a position detector, and a servo amplifier. Our exclusive Diamond Torsion-Bar suspension element supports the pendulum/torque generator Figure 1 assembly (pendulous mass) and allows it to rotate freely about a single pivot axis (while restricting rotation about any other axis). When acceleration is applied to the pendulous mass, our proprietary Position Detector senses pendulum displacement, and converts the amount of deflection into a proportional DC signal. This voltage is amplified by

3 Page 3 the servo amplifier, then fed back through a restoring coil (fixed to the pendulum within a permanent magnetic field), restoring the vane to its null position. The accelerometer output voltage is produced by the restoring current across a sensing (load) resistor in series with the torque coil. When the restoring torque, produced by the interaction of the current in the torque coil and the applied magnetic field, is exactly equal to and opposite that of the torque produced by input acceleration, pendulum movement ceases and net torque equals zero. Thus, this closed-loop servo system provides a pendulous restoring torque directly proportional to the input torque produced by acceleration. The pickoff amplifier, with its very high servo gain, acts as an electronic spring, permitting only minute pendulum deflections even at maximum steady-state input acceleration. (Specifically, the pendulum deflects less than one milliradian in producing a full output signal.) This tight servo pendulum constraint provides inherent accelerometer accuracy, with cross-axis, hysteresis, and linearity errors virtually non-existent. Diamond Torsion Bar Suspension for Environmental Ruggedness: The Model 4384 features our patented Diamond Torsion-Bar suspension system to meet the toughest environmental challenges. This unique suspension element-as opposed to stiff and fragile flexure suspensions-provides free pendulum rotation with low hysteresis and low threshold. Unlike flexure suspensions which produce long-term bias drift, the Model 4384 exhibits high bias stability under extremes of temperature, vibration, and shock. Specifically, the unit can sustain 100g shocks (11 msec), and 25g rms vibrations (bandwidth 20 to 2000 Hz). Dynamic Range Change Provides High Sensitivity: Optional incorporation of our patented Dyna-Range system (Figure 1) provides the Model 4384 with increased high-frequency g-range capability-without sacrificing low-frequency performance. Structural vibrations often result in high frequency signals superimposed on low-frequency accelerometer output. The conventional solution is to attenuate the high frequency signals by filtering output. However, during extremely high-level vibration environments, filtering masks accelerometer saturation, resulting in dynamic non-linearity and output signal errors as high as 10 to 20 percent of full scale. Our Dynamic Range Change incorporates a first-order break (an active filter with 6dB/octave within the servo loop feedback circuit) to provide attenuated high frequency response and improved signal/noise ratio (Figure 2). In addition, our Dynamic Range Change provides added servo current capability for increased g levels at higher frequencies, thus permitting the maximum range of the unit to increase with frequency-without saturation (Figure 3). Figure 2 Signal Frequency Response Figure 3 Typical G-Range Capability vs. Frequency

4 Page 4 Figure 4 indicates acceleration and vibration input information as received by the accelerometer. Figure 5 shows the signal output in a 3g environment with no filtering (a), with low-pass output filtering (b), and with BEI PSSC's Dynamic Range Change (c). Applications: BEI PSSC's Model 4384 Linear Servo Accelerometer is a proven performer for flight control, autopilot, and guidance systems in missile, spacecraft, aircraft, and general instrumentation applications. The Model 4384 offers g-ranges of 1 to 40, with a frequency response of >100 Hz. The unit can be produced in dual-axis or tri-axis sensor packages for majority vote, fly-by-wire flight control system tracking where built-in null offset is required for normal axis. The Model 4384 is designed to operate in hundreds of aircraft, missile, space, and general instrumentation applications, including... Fixed & Rotary Wing-Aircraft # Autopilot systems # Stress measurement # Helicopter stabilization # Pitch g limiters # Angle-of-attack measurement # Measurement of stability derivatives # Landing flare-out controls # Take-off monitors # Fly-by-wire control and tracking # Stall warning systems Missiles # Principle axis determination # Incremental-separation accelerations # Re-entry vehicle instrumentation # Zero-g trajectory indication Typical Options Option A G I J M T Description Input power of ±15 volts D.C. (standard) # Thrust measurement # Sled acceleration monitors General Instrumentation # Elevator accelerations # Vibration in gear hobbing machinery # Railroad car coupling shocks # Leveling inclinometers # Wind loading on service towers # Seismic monitoring Ordering Information: When ordering a Model 4384 Linear Accelerometer, indicate the part number which includes model number, range, and options. Example below right: Electrical connector on case (Viking connector VR7-4AG15). Other connectors available. Adds 1 cm (0.40 in) to case height. Case alignment to true sensitive axis within ± ½ degree. Case alignment to true sensitive axis within ± ¼ degree. Provision for + 1 g internal bias. Dynamic Range Change: DYNA-RANGE provides performance of a low-range servo accelerometer with a moderately restricted frequency response while operating linearly and without saturation under high levels of applied vibration. Figure 4 Acceleration Input Signals Figure 5 Transducer Output Signals (Example) * All units are electrically damped, indicated by the letter A after the model number. ** Symmetrical ranges are indicated by a number designating full scale input in g. For example, a range description of 20 indicates ± 20 g.

5 Page 5 SPECIFICATIONS: Accuracy Physical Non-Linearity <0.05% of full range Range ± 1 g to ± 40 g Hysteresis & Non-repeatability 0.02% of full range Input Power 15vdc ± 10% at 10 ma maximum Resolution 0.001% of full range Voltage Output- Nominal ± 7.5 vdc full scale set to 1% at factory Zero Output (Null) <0.1% of full range Output Impedance 5 kohm nominal Temp. Coeff. of Null (of full range) <0.0018% per /C (<0.001% per /F) Output Current 3 ma full range Output Noise < vrms Electrical Connections 6 solder terminals Cross Axis Sensitivity (Referred to true sensitive axis) <0.002 g/g of applied acceleration Case Alignment (each orthogonal axis) <2/ to true sensitive axis Temp. sensitivity of Scale Factor <0.018% per /C (<0.01% per /F) Weight (typical) 85 grams (3 oz.) Natural Frequency (90/ Phase Shift) (Dependent on g range) Damping Ratio at 22/ (72/F) >100 Hz nominal Size See configuration drawing 0.7 ± 0.1 Other ratios available. Environmental Parameters Temperature Range -54/ C to +93/ C storage (-65/ F to + 200/ F) - 40/ C to +93/ C operating (-40/ F to + 200/ F) Vibration Survival Humidity, Salt, Spray Fungus, Sand & Dust 15 g rms, bandwidth 20 to 2000 Hz (0.12 g 2 per Hz) Hermetically sealed (meets MIL-STD-810B, MIL-E-5272C) Shock Survival 100g, 11 msec Ambient Pressure 0 to 5 atmosphere absolute Special versions are available. Model 4384 Configuration* PIN CONNECTIONS 1 SIGNAL & POWER RETURN 2 I S (SERVO CURRENT OUTPUT) 3 E O (SIGNAL OUTPUT) 4 TEST 5-15V (POWER INPUT) 6 +15V (POWER INPUT) * G option not shown 7 SELF TEST Specifications subject to change without notice.