SAE AS 5391:2002 pdf download

SAE AS 5391:2002 pdf download Health and Usage Monitoring System Accelerometer Interface Specification
Accelerometers are transducers, or sensors, that convert acceleration into an electrical signal whichcan 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 Monitoring System (HUMS). The purpose is tostandardize the accelerometer-to-electronics interface with the intent of increasing interchangeabilityamong HUMS sensors/systems and reducing the cost of HUMS accelerometers. Although this interface was specified with an internally amplified piezoelectric accelerometer in mind, this does notpreclude 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 Association(RITA) compliantHUMS.Compliance with these Interface Specifications can be referenced in more comprehensiveprocurement and device specifications.
1.1 Classification:
Accelerometers used in current HUM systems fall into three distinct categories, they are
a) airframeaccelerometers (generally for rotor track and balance),
b) drive train accelerometers, and c) engineaccelerometers. This document is divided into three sections in recognition of this common industryclassification.
1.2Specification Terminology:
The terms “shall” and “should” within this specification observe the following 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.
3. DEFINITIONS:
ACCELERATION – The time rate of change of velocity – usually expressed in ft/sec/sec, meters/seclsec, or G’s in gravity units (g).
ACCELEROMETER- A sensor whose output varies directly proportionally to the acceleration aspectof motion.
BASE STRAIN SENSITIVY – Unwanted output signal of an accelerometer when its mounting base issubjected to strain by the mounting structure.
BIAS VOLTAGE – A DC voltage at the output of an accelerometer on which an AC motion signal issuperimposed.
CHARGE AMPLIFIER – A capacitive feedback amplifier that converts the high impedance output froma charge mode sensor to a low impedance voltage signal.
CHARGE CONVERTER – Converts the high impedance output of a charge mode sensor to a lowimpedance voltage signal.
CHARGE MODE ACCELEROMETER-A piezoelectric accelerometer that provides a high impedancecharge output signal (without internal electronics).
“g” – Standard unit of acceleration equal to one earth’s gravity at mean sea level – one “g” equals 32.17ftlsec2(FPS) or 9.807 m/s2 (MKS).
GROUND ISOLATION – Refers to a condition when the signal ground is electrically isolated from thetest structure.
NATURAL FREQUENCY – The natural frequency of a spring-mass system is proportional to thesquare root of the ratio of the spring constant to the mass for each degree of freedom.
RESONANCE,MECHANICAL – The condition that occurs when the frequency of an exciting forceequals 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 to astransducer or pickup.
TEMPERATURE RESPONSE- The change in sensor output due to the change in temperature.TRANSDUCER – see Sensor.