In comparing the theoretical performance of sensors, the term eb/q (voltage change due to change In heat transfer) was found to be a fundamental sensor parameter. This was true for both sensitivity and frequency response in both constant current and constant temperature systems. Equations and data are presented for calculating this parameter for most wire and film sensors. Wedges, cones, and other non-cylindrical sensors have not been included because of their special problems at low frequencies due to conduction losses.

Internal cooling of the sensor is used for high temperature environments. Calculations show that the sensitivity at low frequencies as represented by signal-to-noise ratio decreases with cooled sensors. At high frequency, a significant improvement in frequency response can be attained with cooling, particularly when the heat transfer rate between the sensor and its external environment is very low.

The influence of insulating films on the sensor response is also discussed. Both generalized curves and specific data for quartz and polyester are given. In general, modern techniques make it possible to put on protective films that have negligible influence on frequency response.

The extremely high stability of an anemometer system for steady state measurements is shown. The difficulties of contamination, resistance shifts due to strain, and oxidation on tungsten wires has tended to obscure this basic stability. However, with film type sensors and with hot wires in some environments this stability can often be realized.

Meeting Name

Symposium on Turbulence in Liquids (1971: Oct. 4-6, Rolla, MO)


Chemical and Biochemical Engineering

Document Type

Article - Conference proceedings

Presentation Type

Contributed Paper


New Measurement Techniques

Document Version

Final Version

File Type





© 1972 University of Missouri--Rolla, All rights reserved.