The Dwyer 641RM air velocity transmitter combines a hot-wire anemometer that has 16 user-selectable ranges for measuring air velocity in m/s or fpm with a transmitter that provides an isolated 4 to 20 mA output signal proportional to the measured velocity. The hot-wire probe is 12" long for reaching into ductwork and has a 6-ft. long cable that allows the transmitter body to be mounted at a convenient distance from the probe. Designed as a three- or four-wire device, the transmitter has screw terminals for connecting to either an AC or DC power source and to a power or loop receiver (sold separately). An adjustable output filter stabilizes readings when measuring turbulent flow. The unit is for use with clean, dry air and compatible, non-combustible gases. It has European Conformity (CE) marking. Models are available without or with an LED display for observing readings at the point of measurement. The 4-1/2 digit red LED has resolution of 0.01 m/s, 1 fpm (10 fpm at 10,000 and 15,000 fpm ranges). This anemometer is used for monitoring and measuring air flow in HVAC (heating, ventilation, and air conditioning) systems, exhaust stacks and hoods, and clean rooms, among other applications.
|Selectable air velocity ranges||1.25, 2.5, 5, 10, 15, 25, 50, and 75 m/s; 250, 500, 1,000, 2,000, 3,000, 5,000, 10,000, and 15,000 fpm|
|Air velocity accuracy||3% of full scale with process air at 0 to 50 degrees C/32 to 122 degrees F; 4% of full scale with process air at -40 to 0 degrees C/-40 to +32 degrees F and 50 to 100 degrees C/122 to 212 degrees F|
|Power||12 to 35VDC or 10 to 16VAC, 1.5 amp|
|Output signal||4 to 20 mA, isolated 24V source, 3- or 4-wire connection|
|Maximum loop resistance||600Î©|
|Pressure rating||100 psi/6.89 bar|
|Temperature rating||Process air: -40 to +100 degrees C/-40 to +212 degrees F; ambient air: 0 to 60 degrees C/32 to 140 degrees F|
|Probe diameter||0.79 cm/5/16"|
|Transmitter length||126.21 mm/4-31/32"|
|Weight||Without LED: 374.26 g/13.2 oz.; with LED: 394.16 g/13. oz.|
Anemometers, also called wind meters, measure air velocity and are most commonly used for weather monitoring to determine wind speed and for HVAC applications to determine air flow within ducts. In addition to air velocity, anemometers may measure wind direction, air pressure, air flow volume, air temperature, humidity, light, and other properties. The most common types of anemometer are cup, vane, hot-wire, and Pitot tube. Cup and vane anemometers calculate air velocity based on the number of rotations of the cups or vane. Hot-wire anemometers calculate air velocity by measuring the change in electrical resistance as air flow cools a heated wire. Pitot tube anemometers measure air pressure within a tube and calculate air velocity based on the difference in pressure between the air inside and outside of the tube. Many anemometers have digital readouts and can display air velocity readings in different units of measure, such as meters per second (m/s), feet per minute (ft./min. or fpm), knots, miles per hour (mph), and kilometers per hour (km/h).
Dwyer Instruments manufactures measurement and control instruments, including pressure gauges, flow meters, level instrumentation, temperature instrumentation, and air quality monitors. The company, founded in 1931, is headquartered in Michigan City, IN.