Calibration Systems and Services

Advanced microphones, such as those developed by Endevco, are used for the measurement of high-intensity sound (> 95 dB SPL). Typical applications include near-field measurements of jet aircraft engines, testing and evaluation of rocket motors, and other similar environments. While accelerometers measure vibration of a structure, microphones measure airborne sound (or pressure). Since sound is produced by mechanical vibrations, understanding the mechanical structure producing the vibrations that emit sound and the dynamic characteristics of that structure becomes very important. In-depth knowledge of structural vibration will lead engineers to solutions for reducing problematic sound levels. Fortunately, stating the sensitivity of microphones in V/Pa (volts/pascal) is ... Read Full Story

Basic application parameters often drive which type of device to select. Using Endevco as an example again, the are limited to 150g or less (one measures ±2g, full scale). But it is also important to keep in mind that Endevco Microtron® devices have 20,000g survivability. This extreme overrange capability is the result of the unique design of the Endevco Microtron accelerometer . VC devices, with their high sensitivity, are well suited for testing automotive suspension systems, measuring aircraft flutter , safety testing of amusement park rides, and control of specialized railroad passenger cars. PR devices are excellent shock accelerometers , with the capability of ... Read Full Story

The need to measure shock phenomena has become a very important aspect in recent years. In the past much shock information has been in the form of whether a piece of equipment will withstand specific shock as produced by shock machines . But these machines are not necessarily accurate; therefore the chance of malfunction when those tested sensors are subjected to specific fields. In present flight and missile field, size and weight have become very important factors so that large safety factors cannot be built into the systems. Therefore, accurate information is needed as to the shock phenomena that are expected during the operation ... Read Full Story

Piezoelectric accelerometers are the first choice for most vibration measurements since they have a wide frequency response, good sensitivity and resolution and are easy to install. There are two subdivisions of piezoelectric accelerometers which include the basic charge-mode accelerometer and the voltage mode Internal Electronic Piezoelectric (IEPE) types. IEPE Piezoelectric In recent years, the IEPE type has become the most commonly used accelerometer type. IEPE sensors are often sold under different trade marked names, but all virtually comply with a pseudo industry standard and are interchangeable between brand names. Basically, an IEPE accelerometer is a device with the charge amplifier built-into the accelerometer. They require no external charge amplifiers and use ordinary low cost l cable. The accelerometer does require ... Read Full Story

Mounted resonant frequency is the point in frequency in the accelerometer’s frequency response where the accelerometer outputs maximum sensitivity . It is specified in units of hertz (Hz). Typical accelerometers exhibit a mounted resonant frequency above 20 kHz, although some show as high as 90 kHz.   As the name implies, it is the result of the natural resonance of the mechanical structure of the accelerometer itself.   [Certainly if the resonance of the accelerometer were measured in “free space” it would be different than if mounted to a structure.   However, this is an impractical application for a piezoelectric accelerometer , thus the ... Read Full Story