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BEI Precision Systems & Space Company, Inc. 10/2010 1100 Murphy Drive # Maumelle, AR 72113 USA # Tel: 501-851-4000 # Fax: 501-851-5476 MM-046B

MODEL 4384LINEAR SERVOACCELEROMETERThe proven performer for flight control,autopilot, guidance, and instrumentationapplications in missile, spacecraft, andaircraft systems. This highly sensitivelinear servo accelerometer providesextremely accurate low-level accelerationmeasurement under high levels ofenvironmental vibration and shock.

ACCELEROMETER SPECIFICATIONModel 4384 LINEAR SERVO ACCELEROMETER

Approved for general release.

Page 2 Accelerometer Specification


BEI Precision Systems and Space Company's Model 4384 Linear Servo Accelerometer provides a standardproduct approach to meet your flight control, guidance, and instrumentation system demands. Originallydeveloped as an advanced, ruggedized version of our Model 4310 series accelerometers, we designed the Model4384 specifically for high-volume production.

Design Benefits: Accelerometer reliability and performance are important prerequisities in order to achieveoverall system goals. The Model 4384 consistently meets program requirements, featuring:

Qualified and Proven Design: The Model 4384 has qualified for extensive commercial and military aerospaceapplications, 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 theModel 4384 with increased high-frequency g-range capability — without saturation, distortion, or biasoffsets-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 otherthermal 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 totalsensing system weighs less than 300 milligrams. Contains virtually no moving parts, and requires nomaintenance.

# Self-Test Capability: Contains built-in test (BIT), utilizing an external current source for flight controlcheck-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 scheduledemanded by major programs.

# Quality Production Capability: The standard manufacturing, inspection, and quality control systems at BEIPSSC meet ISO 9001:2008, as well as stringent NASA requirements.

Technical Design and Theory of Operation: TheModel 4384 operates on the torque balance principleemployed in all BEI PSSD accelerometers. Weincorporated our exclusive Diamond Torsion-Barsuspension system and our patented PositionDetector to design a highly accurate, extremelyrugged sensor.

As indicated in Figure 1, the unit consists of alightweight vane attached to a torque generator, aposition detector, and a servo amplifier.

Our exclusive Diamond Torsion-Bar suspensionelement supports the pendulum/torque generatorassembly (pendulous mass) and allows it to rotatefreely 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 pendulumdisplacement, and converts the amount of deflection into a proportional DC signal. This voltage is amplified by

Figure 1



the servo amplifier, then fed back through a restoring coil (fixed to the pendulum within a permanent magneticfield), restoring the vane to its null position.

The accelerometer output voltage is produced by the restoring current across a sensing (load) resistor in serieswith the torque coil. When the restoring torque, produced by the interaction of the current in the torque coiland the applied magnetic field, is exactly equal to and opposite that of the torque produced by inputacceleration, pendulum movement ceases and net torque equals zero. Thus, this closed-loop servo systemprovides 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 pendulumdeflections even at maximum steady-state input acceleration. (Specifically, the pendulum deflects less than onemilliradian in producing a full output signal.) This tight servo pendulum constraint provides inherentaccelerometer accuracy, with cross-axis, hysteresis, and linearity errors virtually non-existent.

Diamond Torsion Bar Suspension for Environmental Ruggedness: The Model 4384 features our patentedDiamond Torsion-Bar suspension system to meet the toughest environmental challenges. This uniquesuspension element-as opposed to stiff and fragile flexure suspensions-provides free pendulum rotation withlow hysteresis and low threshold. Unlike flexure suspensions which produce long-term bias drift, the Model 4384exhibits high bias stability under extremes of temperature, vibration, and shock. Specifically, the unit can sustain100g 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 sacrificinglow-frequency performance.

Structural vibrations often result in high frequency signals superimposed on low-frequency accelerometeroutput.

The conventional solution is to attenuate the high frequency signals by filtering output. However, duringextremely high-level vibration environments, filtering masks accelerometer saturation, resulting in dynamicnon-linearity and output signal errors as high as 10 to 20 percent of full scale.

Our Dynamic Range Changeincorporates a first-order break (anactive filter with 6dB/octave within theservo loop feedback circuit) to provideattenuated high frequency responseand improved signal/noise ratio (Figure2).

In addition, our Dynamic Range Changeprovides added servo current capabilityfor increased g levels at higherfrequencies, thus permitting themaximum range of the unit to increasewith frequency-without saturation (Figure3).

Figure 3Typical G-RangeCapabilityvs. Frequency

Figure 2SignalFrequencyResponse



Figure 4 indicates acceleration and vibration input information asreceived 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 DynamicRange Change (c).

Applications: BEI PSSC's Model 4384 Linear Servo Accelerometer is aproven performer for flight control, autopilot, and guidance systemsin missile, spacecraft, aircraft, and general instrumentationapplications.

The Model 4384 offers g-ranges of 1 to 40, with a frequency responseof >100 Hz. The unit can be produced in dual-axis or tri-axis sensorpackages for majority vote, fly-by-wire flight control system trackingwhere 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 systemsMissiles# Principle axis determination# Incremental-separation

accelerations# Re-entry vehicle instrumentation# Zero-g trajectory indication

# Thrust measurement# Sled acceleration monitorsGeneral Instrumentation# Elevator accelerations# Vibration in gear hobbing

machinery# Railroad car coupling shocks# Leveling inclinometers# Wind loading on service towers# Seismic monitoring

Ordering Information: Whenordering a Model 4384 LinearAccelerometer, indicate the partnumber which includes modelnumber, range, and options.Example below right:

Typical Options

Option Description

A Input power of ±15 volts D.C. (standard)

GElectrical connector on case (Viking connector VR7-4AG15).Other connectors available. Adds 1 cm (0.40 in) to case height.

I Case alignment to true sensitive axis within ± ½ degree.

J Case alignment to true sensitive axis within ± ¼ degree.

M Provision for + 1 g internal bias.

T

Dynamic Range Change: “DYNA-RANGE™” provides performanceof a low-range servo accelerometer with a moderately restrictedfrequency response while operating linearly and withoutsaturation under high levels of applied vibration.

* All units are electrically damped,indicated by the letter “A” after themodel number.

** Symmetrical ranges are indicated by anumber designating full scale input ing. For example, a range description of20 indicates ± 20 g.

Figure 4 Acceleration InputSignals

Figure 5 Transducer Output Signals(Example)



PIN CONNECTIONS

1 SIGNAL & POWER RETURN

2 IS (SERVO CURRENT OUTPUT)

3 EO (SIGNAL OUTPUT)

4 TEST

5 -15V (POWER INPUT)

6 +15V (POWER INPUT)

7 SELF TEST

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% at10 ma maximum

Resolution 0.001% of full range Voltage Output-Nominal

± 7.5 vdc full scaleset 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 <0.0075 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 ScaleFactor

<0.018% per /C (<0.01% per /F)

Weight (typical) 85 grams (3 oz.)

Natural Frequency(90/ Phase Shift)(Dependent on g range)

>100 Hz nominal Size See configuration drawing

Damping Ratioat 22/ (72/F)

0.7 ± 0.1Other 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 15 g rms, bandwidth 20 to 2000 Hz(0.12 g2 per Hz)

Humidity, Salt , SprayFungus, Sand & Dust

Hermetically sealed(meets MIL-STD-810B, MIL-E-5272C)

Shock Survival 100g, 11 msec Ambient Pressure 0 to 5 atmosphere absoluteSpecial versions are available.

Model 4384 Configuration*

* G option not shown

Specifications subject to change without notice.