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TPI-575/C1 Vane and Hotwire Velocity Meter

Features

• (Vane) Air flow 0.4 to 25 m/s (Also reads km/s, ft/min, knots/h, miles/h)

• (Hotwire ) Air flow 0.2 to 20 m/s (Also reads km/s, ft/min, knots/h, miles/h

• Temperature -5° to 175° F (-20° to 80°C)

• Data record function for maximum and minimum temperature and air velocity reading

• Download to a computer using the RS-232 port and optional A500 cable.

(The 555 uses Microsoft® Hyper Terminal to download and display air velocity and

temperature on your PC.)

• 39” cable length with Lemo connector

• Data Hold

• Auto Power Off

• Protective boot and soft carrying case included

Model 575C1 Specifications
Air Velocity (Low friction ball conventional twist wheel)	80 to 4900 ft/min 0.4 to 25 m/s 40 to 3900 ft/min 0.2 to 20 m/s
Units of Measure	m/s, km/s, ft/min, mile/hr, knots/hr
Air Velocity Accuracy	±(2% of rdg + 3 digits) vane >±(5% of rdg + 3 digits) hot wire
Temperature (Precision thermistor)	-5°F to 175°F -20°C to 80°C
Temperature Accuracy	±(1% of rdg + 1°F + 3 digits)
Units of Measure	°C / °F
CFM Calculation	Manual using formula
RS-232 Output	Yes
Min/Max Record	Yes
Operating Temperature (Base Unit)	32°F to 122°F
Operating Humidity (Base Unit)	<95% non-condensing
Battery Type	9V
Battery Life	30 hours typical
Dimension W x L x H	2.9” x 5.7” x 1.1”
Weight	0.3lb

http://www.testproductsintl.com/575C1.html#&slider1=1

How To Measure Velocity And Flow

In HVAC/R applications it is helpful to understand the methods used to determine air velocity. Air velocity (distance traveled per unit of time) is most often expressed in feet per minute (FPM). Multiplying air velocity by the area of a duct allows you to determine the air volume flowing past a point in the duct per unit of time. Volume flow is generally measured in cubic feet per minute (CFM).

Air velocity is measured by sensing the pressure that is produced through the movement of the air. Velocity is also related to air density with assumed constants of 70° F and 29.92 in Hg. The two most common technologies to measure velocity are capacitive based pressure sensors and hot-wire anemometers. There are two types of pressure that need to be known to measure velocity; total pressure and static pressure. Both can be measured using a Pitot or averaging tube. Velocity pressure is calculated by taking the difference of the total pressure and static pressure. To measure the velocity pressure, connect a Pitot or averaging tube to a velocity sensor and place the tube into the air flow of the duct. The actual velocity requires either a mathematical calculation or a calibrated sensor that directly shows velocity.

V = 4005 x square root (delta P)

Delta P=( pressure change in inches WC)
V= Velocity(ft/min)

Determining air flow is a matter of multiplying the cross sectional area of a duct by the air velocity. If the dimensions of the duct are known, then the cross-sectional area can be easily determined and the volumetric flow calculated. The one thing to keep in mind is that the air velocity is not uniform at all points of the duct. This is true because the velocity is lowest at the sides where the air is slowed down by friction. To account for this, using an averaging Pitot tube with multiple sensing points will more accurately reflect the average velocity.

Q (air flow rate)= A (area of duct) * V (air velocity)

Importance of measuring Velocity

Improve system performance
Increase energy efficiency and cost savings- Knowing ACH (increase or decrease usage)
Maintain proper air flow rates to ensure occupant comfort
Measure air flow for critical spaces or high traffic areas

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