1、SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirelyvoluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefro
2、m, is the sole responsibility of the user.”SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions.Copyright 2002 Society of Automotive Engineers, Inc.All rights reserved. No part of this
3、 publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE.TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada)Tel: 724-776-4970 (
4、outside USA)Fax: 724-776-0790Email: custsvcsae.orgSAE WEB ADDRESS: http:/www.sae.orgAEROSPACE STANDARDAS5391Issued 2002-12Health and Usage Monitoring SystemAccelerometer Interface SpecificationTABLE OF CONTENTS1. SCOPE .31.1 Classification.31.2 Specification Terminology .32. REFERENCES .33. DEFINITI
5、ONS.44. REQUIREMENTS AND RECOMMENDATIONS 54.1 HUMS Airframe Accelerometers.54.1.1 Definition .54.1.2 Characteristics 54.2 HUMS Drive Train Accelerometers.104.2.1 Definition .104.2.2 Characteristics 104.3 HUMS Engine Accelerometers .154.3.1 Definition .154.3.2 Characteristics 165. NOTES .195.1 Cable
6、Tie Down for Performance Testing 19Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-SAE AS5391 - 2 -TABLE OF CONTENTS (Continued)FIGURE 1 Allowable Airframe Accelerometer Amplitude Response.6FIGURE 2 Al
7、lowable Airframe Accelerometer Relative Phase Response.7FIGURE 3 Allowable Drive Train Accelerometer Amplitude Response.11FIGURE 4 Allowable Drive Train Accelerometer Relative Phase Response.12FIGURE 5 Allowable Engine Accelerometer Amplitude Response .16FIGURE 6 Allowable Engine Accelerometer Relat
8、ive Phase Response .17FIGURE 7 Cable Tie Down for “Donut“ Style Accelerometer 19FIGURE 8 Cable Tie Down for “Spark Plug“ Style Accelerometer 19TABLE 1 Airframe Accelerometer Connector Pin Assignments Option #1 .9TABLE 2 Airframe Accelerometer Connector Pin Assignments Option #2 .10TABLE 3 Drive Trai
9、n Accelerometer Connector Pin Assignments Option #114TABLE 4 Drive Train Accelerometer Connector Pin Assignments Option #215Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-SAE AS5391 - 3 -1. SCOPE:Acce
10、lerometers are transducers, or sensors, that convert acceleration into an electrical signal which can be used for vibration monitoring and analysis.This document defines interface requirements for accelerometers and associated interfacing electronics for use in a helicopter Health and Usage Monitori
11、ng System (HUMS). The purpose is to standardize the accelerometer-to-electronics interface with the intent of increasing interchangeability among HUMS sensors/systems and reducing the cost of HUMS accelerometers. Although this interface was specified with an internally amplified piezoelectric accele
12、rometer in mind, this does not preclude the use of any other sensor technology that meets the requirements given in this specification.These SAE HUMS Interface Specifications include the minimal interface and performance requirements for interoperability with the Rotorcraft Industry Technology Assoc
13、iation (RITA) compliant HUMS. Compliance with these Interface Specifications can be referenced in more comprehensive procurement and device specifications.1.1 Classification:Accelerometers used in current HUM systems fall into three distinct categories, they are a) airframe accelerometers (generally
14、 for rotor track and balance), b) drive train accelerometers, and c) engine accelerometers. This document is divided into three sections in recognition of this common industry classification.1.2 Specification Terminology:The terms “shall“ and “should“ within this specification observe the following
15、rules:a. The word “shall“ expresses a mandatory requirement of the specification.b. The word “should“ expresses a recommendation or advice on implementing the specification or actions expected of users of the system.2. REFERENCES:There are no referenced publications specified herein.Copyright SAE In
16、ternational Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-SAE AS5391 - 4 -3. DEFINITIONS:ACCELERATION - The time rate of change of velocity - usually expressed in ft/sec/sec, meters/sec/sec, or Gs in gravity units (g).ACCELEROM
17、ETER - A sensor whose output varies directly proportionally to the acceleration aspect of motion.BASE STRAIN SENSITIVY - Unwanted output signal of an accelerometer when its mounting base is subjected to strain by the mounting structure.BIAS VOLTAGE - A DC voltage at the output of an accelerometer on
18、 which an AC motion signal is superimposed.CHARGE AMPLIFIER - A capacitive feedback amplifier that converts the high impedance output from a charge mode sensor to a low impedance voltage signal.CHARGE CONVERTER - Converts the high impedance output of a charge mode sensor to a low impedance voltage s
19、ignal.CHARGE MODE ACCELEROMETER - A piezoelectric accelerometer that provides a high impedance charge output signal (without internal electronics).“g“ - Standard unit of acceleration equal to one earths gravity at mean sea level - one “g“ equals 32.17 ft/sec2(FPS) or 9.807 m/s2(MKS).GROUND ISOLATION
20、 - Refers to a condition when the signal ground is electrically isolated from the test structure. NATURAL FREQUENCY - The natural frequency of a spring-mass system is proportional to the square root of the ratio of the spring constant to the mass for each degree of freedom.RESONANCE, MECHANICAL - Th
21、e condition that occurs when the frequency of an exciting force equals a natural frequency of a spring-mass system.SENSITIVITY - The ratio of change in sensor output as a result of a unit change in measurand.SENSOR - A measurement device that transforms one form of energy into another. Also referred
22、 to as transducer or pickup.TEMPERATURE RESPONSE - The change in sensor output due to the change in temperature. TRANSDUCER - see Sensor.Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-SAE AS5391 - 5 -
23、3. (Continued):TRANSVERSE SENSITIVITY - The unwanted output signal of a motion sensor when subjected to motion perpendicular to the sensitive axis - usually expressed as a percentage of the normal axis sensitivity.4. REQUIREMENTS AND RECOMMENDATIONS:The specific functional requirements for the three
24、 sensor types are given in the following subparagraphs.4.1 HUMS Airframe Accelerometers:4.1.1 Definition: Airframe (i.e., rotor balance) accelerometers measure airframe vibration, which usually results from rotor imbalance conditions. Rotor imbalance conditions cause rotor one per revolution disturb
25、ances. These disturbances result in airframe vibrations in the frequency range from two hertz to tens of hertz. In addition, some Rotor Balance algorithms utilize higher harmonic vibrations (2 per rev up to 24 per rev).4.1.2 Characteristics: HUMS airframe accelerometers shall have a low impedance vo
26、ltage output (i.e., internal conditioning), directly proportional to the acceleration. Measurement of static (0 Hz) acceleration is not required for airframe vibration monitoring. Experience has shown that the measurement of airframe acceleration is easily corrupted by strain in the mounting base of
27、 the accelerometer that results in unwanted output signal. This vulnerability to strain on the accelerometers mounting base requires the use of an accelerometer with low base strain sensitivity (given in 4.1.2.4.3). The accelerometer signal return will be isolated, internally, from case ground. Prec
28、ise measurement of phase is required in RT&B applications to determine which blade or combination of blades is causing an out of balance condition. Two body styles are recommended for HUMS airframe accelerometers. Multiple body styles are needed to accommodate the sensor installation requirements fo
29、r rotorcraft from multiple aircraft manufacturers.4.1.2.1 Performance: Performance requirements should be met using mounting hardware, cables and connectors as recommended in 4.1.2.3. Performance testing should be performed with cables tied down as specified in 5.1 of this document.4.1.2.1.1 Sensiti
30、vity: The sensitivity should be 50 mV/g, 5% when measured at 100Hz 5 Hz or 120 Hz 5 Hz.4.1.2.1.2 Acceleration Range: The acceleration range shall be 100 g.4.1.2.1.3 Frequency Response:Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permit
31、ted without license from IHS-,-SAE AS5391 - 6 -4.1.2.1.3.1 Amplitude Response: The amplitude response of the sensor should lie in the unshaded region of the frequency response plot of Figure 1. The y-axis is given in units of % deviation as defined in Equation 1.(Eq. 1)FIGURE 1 - Allowable Airframe
32、Accelerometer Amplitude Response4.1.2.1.3.2 Relative Phase Response: The phase response of the sensor should lie in the unshaded region of the phase response plot of Figure 2. The y-axis (phase dispersion), in the figure below, is the phase of the sensors output relative to a reference accelerometer
33、 and normalized to the value at 100 Hz 5 Hz or 120 Hz 5 Hz. The phase data is normalized by removing the relative phase (phase difference between the sensor under test and the reference accelerometer) at 100 Hz 5 Hz or 120 Hz 5 Hz from the rest of the test data. As a result, the curve in Figure 2 wi
34、ll always pass through the point of 0 of phase dispersion at 100 Hz 5 Hz or 120 Hz 5 Hz.% DeviationSensor Output - Sensor Output 100 or 120 HzSensor Output 100 or 120 Hz-100%=Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted witho
35、ut license from IHS-,-SAE AS5391 - 7 -FIGURE 2 - Allowable Airframe Accelerometer Relative Phase Response4.1.2.1.3.3 Absolute Phase Lag: The phase difference between the position of the sensor and the sensors electrical output shall be 0 5 when excited with 2 Hz acceleration.4.1.2.1.3.4 Mounted Reso
36、nance Frequency: The mounted resonance frequency of the accelerometer should be greater than 30 kHz. 4.1.2.1.4 Output Polarity: Positive acceleration into the base of the accelerometer shall produce a positive output voltage. Positive acceleration shall be in the direction pointing through the accel
37、erometers mounting base towards its mounting structural point. Neglecting the DC output bias, positive output voltage shall be defined as when the connector signal or power pin shall have a greater voltage than the signal common pin.4.1.2.1.5 Transverse Sensitivity: The transverse sensitivity of the
38、 accelerometer shall be less than or equal to 5% of the sensitivity of the primary axis (given in 4.1.2.1.1).4.1.2.1.6 Temperature Response: The sensitivity of the sensor shall vary less than 5%, with respect to the sensitivity at room temperature 24 C 2 C (75 F 4 F), over the temperature range give
39、n in 4.1.2.4.1.4.1.2.2 Electrical: The accelerometer is a two-wire device. The two-wire interface carries the electrical power to the accelerometer as well as the acceleration signal to the interface electronics. The accelerometer will accept electrical power from a constant current regulated DC vol
40、tage source.4.1.2.2.1 Supply Current: The accelerometer shall operate continuously with 4 mA 1 mA current from a constant current regulated DC voltage source. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from
41、IHS-,-SAE AS5391 - 8 -4.1.2.2.2 Maximum Supply Voltage: The maximum voltage supplied to the accelerometer shall not exceed 32 V DC even under transient conditions.4.1.2.2.3 DC Output Bias Voltage: The accelerometer output shall consist of a +7 to +13 V DC bias on which an AC signal, proportional to
42、the acceleration, is superimposed.4.1.2.2.4 Full Scale Output Voltage: The accelerometer output shall consist of a 5 volt (peak) AC signal that is directly proportional to the vibratory acceleration and is superimposed on a DC bias voltage.4.1.2.2.5 Electrical Isolation: The accelerometers output si
43、gnal common shall be internally isolated (20 M 50 V DC) from case ground.4.1.2.2.6 Output Impedance: The output impedance shall be less than 200 over the acceleration range specified in 4.1.2.1.2.4.1.2.2.7 Case Resistance: The electrical resistance between the connectors “case“ pin and any point on
44、the accelerometer body shall not exceed 2.5 m.4.1.2.3 Physical Characteristic Recommendations: Two body styles are recommended for HUMS airframe accelerometers. These multiple body styles will support sensor installation requirements for rotorcraft from multiple aircraft manufacturers. They are: a)
45、the through bolt mounted (“donut“ style) accelerometer, and b) the tapped hole & stud mounted (“spark plug“ style) accelerometer. 4.1.2.3.1 “Donut“ Style Sensor Body: This accelerometer body is a center throughbolt design. 4.1.2.3.1.1 Weight: The weight of the accelerometer, excluding fasteners and
46、integral cable, should be less than 60 grams.4.1.2.3.1.2 Size: The dimensions of the accelerometer, excluding mounting hardware and integral electrical cable should be less than 1.2 inches (30.5 mm) wide, 1.2 inches (30.5 mm) deep and 0.9 inches (22.9 mm) high.4.1.2.3.1.3 Cable Strain Relief & Leak
47、Rate: The HUMS donut style, airframe, accelerometer should have an integral cable with strain relief where the cable exits the sensor body. The integral cable and strain relief should provide a minimum pull strength of 40 pounds (178 N). The accelerometer case, and the accelerometer case-to-cable in
48、terface, shall be hermetically sealed with a leak rate of less than 1 x 10-8cm2/sec over the temperature range specified in 4.1.2.4.1.4.1.2.3.1.4 Integral Cable: The accelerometer should have a side exiting integral cable. The integral cable should consist of a twisted shielded pair of 22 gauge wires. The two wires should carry the output signal and the output signal common. The cable shield should be connected to the accelerometer case ground. The integral cable should be 20 feet (6.1 m) long and unterminated (no connector). Copyright SAE International Prov
