thermal isolator - Vibra·Metrics - #1

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Vibra «Metrics Thermal Isolator y A Hemix* ot MISTRAS HMoç* Group Thermal Isolator for IEPE accelerometers In high température applications which exceed the température limits of IEPE (Integrated Electronic Piezo-Electric) accelerometers, and where the cost or the disadvantages of charge-type accelerometers and charge amplifters are prohibitive, it is possible to use a Thermal Isolator with a low cost IEPE type accelerometer to measure vibration on elevated température surfaces. It is important to note that ambi-ent température must be substantially lower for any significant réduction in température at the acceler­ometer mounting surface. As an example, a Thermal Isolator was tested on a surface with a constant 220 C température, with an ambient, circulating air température of 22 C. The graph below shows the température response at the opposite end of the Thermal Isolator (the accelerometer mounting surface). The red line represents the surface température, while the blue line represent the accelerometer mounting surface. An equilibrium température of ÎOS C was reached after approximately 30 minutes opération. This represents a differen-tial of 115C, which is iikely the highest température differential we might expect to achieve. Is is most important to note that except for the Thermal Isolator's low thermal conductivity, the cool, circulating air is the largest factor allowing this température differential. Since most IEPE accelerometers will function to 120 C, we can conclude that it is possible to use IEPE accelerometers with a Thermal Isolator on surface températures up to 235 C and still obtain reasonable data, without damaging the sensor. Note that in the long term, accelerometer life will be reduced at higher températures. Time vs. Température 250 200 e iso I 0 -1-■-1-1-p-1-■- 0 tO 20 30 40 50 60 70 80 îkn* (minute*) Equipment Used: xxx Hotplate, Fluke xxxx, Model 1018 accelerometer 195 Clarksvillc Road, Princeton Junclion, NJ 08550 • Phone: 609 716 4130 • Fax: 609 716 0706 Email: salcs@vibraniclrics.com • Internet: www.viforamctrics.com Due to contmutng improvement, Vibrs-Metrics reserves the nght to smend spécifications wtthout notice Copyright © 2003 MISTMS Holdings Group. Ail Rtghts Reserved. Rev. 11/03 VM*114703 page 1/?