A temperature-compensated thermo-anemometer for use in non-isothermal boundary layers

✍ Scribed by Koppius, A. M. ;Vries, D. A.

• Publisher: Springer
• Year: 1966
• Tongue: English
• Weight: 490 KB
• Volume: 16
• Category: Article
• ISSN: 0003-6994
• DOI: 10.1007/bf00384067

✦ Synopsis

An anemometer has been constructed using a small bead shaped thermistor (dimensions ~ 1 mm) as the sensitive element for measuring flow velocities. A much bigger disc shaped thermistor (diameter ~ 5 mm, thickness ~ 2 mm), mounted in the measuring head, is used for measuring the temperature of the flowing gas and for compensating the flow measurement for changes in gas temperature over a range of about 50°C.

The principle of the compensating action rests on two conditions: (i) the small thermistor is heated in such a way that its temperature is higher than that of the big thermistor by a fixed amount (77°C in the instrument described here); (2) the big thermistor has the same resistance-temperature dependence as the small one at the higher temperature. Condition (2) is satisfied by placing properly chosen resistors in series and parallel with the big thermistor.

A theoretical analysis is presented of the operation of the instrument. Experimental results can be accounted for by this theory in a satisfactory manner.