In high temperature applications which exceed the temperature limits of IEPE (Integrated Electronic Piezo-Electric) accelerometers, and where the cost or the disadvantages of charge-type accelerometers and charge amplifiers are prohibitive, it is possible to use a Thermal Isolator with a low cost IEPE type accelerometer to measure vibration on elevated temperature surfaces. It is important to note that ambient temperature must be substantially lower for any significant reduction in temperature at the accelerometer mounting surface.
As an example, a Thermal Isolator was tested on a surface with a constant 220 C temperature, with an ambient, circulating air temperature of 22 C. The graph below shows the temperature response at the opposite end of the Thermal Isolator (the accelerometer mounting surface). The red line represents the surface temperature, while the blue line represent the accelerometer mounting surface. An equilibrium temperature of 105 C was reached after approximately 30 minutes operation. This represents a differential of 115C, which is likely the highest temperature 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 temperature 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 temperatures 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 temperatures.