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 Overview The Hot-Wire Anemometer is the most well known thermal anemometer, and measures a fluid velocity by noting the heat convected away by the fluid. The core of the anemometer is an exposed hot wire either heated up by a constant current or maintained at a constant temperature (refer to the schematic below). In either case, the heat lost to fluid convection is a function of the fluid velocity. Typical Hot-Wire Anemometer By measuring the change in wire temperature under constant current or the current required to maintain a constant wire temperature, the heat lost can be obtained. The heat lost can then be converted into a fluid velocity in accordance with convective theory.
 Further Information Typically, the anemometer wire is made of platinum or tungsten and is 4 ~ 10 µm (158 ~ 393 µin) in diameter and 1 mm (0.04 in) in length. Typical commercially available hot-wire anemometers have a flat frequency response (< 3 dB) up to 17 kHz at the average velocity of 9.1 m/s (30 ft/s), 30 kHz at 30.5 m/s (100 ft/s), or 50 kHz at 91 m/s (300 ft/s). Due to the tiny size of the wire, it is fragile and thus suitable only for clean gas flows. In liquid flow or rugged gas flow, a platinum hot-film coated on a 25 ~ 150 mm (1 ~ 6 in) diameter quartz fiber or hollow glass tube can be used instead, as shown in the schematic below. Another alternative is a pyrex glass wedge coated with a thin platinum hot-film at the edge tip, as shown schematically below.
Pros and Cons

 • Pros: - Excellent spatial resolution. - High frequency response, > 10 kHz (up to 400 kHz). • Cons: - Fragile, can be used only in clean gas flows. - Needs to be recalibrated frequently due to dust accumulation (unless the flow is very clean). - High cost.
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STEM Career Outlook

Wages, employment opportunities, and growth projections for STEM jobs.

Mechanical Engineers Outlook

Guide for those interested in becoming a mechanical engineer. Includes qualifications, pay, and job duties.

Salary Expectation

8 things to know about the interview question "What's your salary expectation"?

Metal 3D Printing Design Guide

Direct Metal Laser Sintering (DMLS) 3D printing for parts with reduced cost and little waste.