Can I buy one hood for the AccuBalance® Air Capture Hood?
The AccuBalance® Air Capture Hood comes standard with a 2-foot x 2-foot hood. Additional hoods can either be purchased in kits or individually.
Can the AccuBalance® Air Capture Hood read to zero CFM?
The AccuBalance® Air Capture Hood will accurately read as low as 30 CFM. Below this flowrate, a flashing 0 will be displayed.
Do you need to correct for humidity?
There is no need to correct for humidity because humidity has very little affect on velocity readings. Studies show there is less than a 3-percent change in the velocity reading while the humidity changes from 0 to 100-percent RH in air at room temperature.
Does the hot-wire sensor need to be cleaned in the field to assure accurate readings?
No. We found the sensors have remained clean on all of the AccuBalance® Air Capture Hoods returned for recalibration.
How long is the warranty period?
The AccuBalance® Air Capture Hood has a warranty period of two years. See the instruction manual for details.
How much does the AccuBalance® Air Capture Hood weigh?
The AccuBalance® Air Capture Hood is the lightest flow capture hood in the industry. Using a 2-foot x 2-foot hood, the AccuBalance hood weighs less than 7-1/2 pounds (3.4 kg).
How often should I have the AccuBalance® Air Capture Hood calibrated?
To maintain a high degree of accuracy in your measurements, TSI recommends that you return the instrument to the factory for annual calibration. Typical turn-around time is two business days when the unit is received with proper documentation.
Is it back-pressure compensated?
The AccuBalance® Air Capture Hood has a very low amount of back pressure and is not back-pressure compensated. A graph showing the pressure drop through the AccuBalance hood and a method to calculate a correction factor can be found in Application Note TI-128.
Please explain NIST traceability
NIST is the National Institute of Standards and Technology. All test and calibration data supplied by TSI has been obtained using standards whose accuracies are traceable to NIST or has been verified with respect to instrumentation whose accuracy is traceable to NIST.
What about this LIGHT key?
The back light key will turn the back light on and off. When the back light is not needed, we recommend it be turned off, because it will shorten the life of the batteries if it is left on.
What are density corrections?
In general, there are two ways to express air velocity: standard velocity and actual velocity. Standard velocity is velocity that is referenced to standard conditions. Actual velocity is the speed at which a microscopic particle of dust would be traveling as the air flow carries it along. The two measurements give the same readings if actual conditions equal standard conditions. However, if the temperature increases, the air would expand and become thinner. Actual velocity would then be higher than standard velocity. The Model 8705 DP-Calc™ Micromanometer can display either actual or standard velocity when barometric pressure and temperature are entered.Density Correction Factor = ((460+70)(P)) / ((460+T)(406.8))whereT = ambient temperature in degrees FahrenheitP = ambient pressure in inches H2O.If you use metric units, the equation becomes:Density Correction Factor = ((273.15+21.1)(Pm)) / ((273.15+Tm)(101.3))whereTm = ambient temperature in degrees CentigradePm = ambient pressure in kPa.The density correction factor will generally be a value in the range of 0.3 to 1.7, depending on the ambient conditions.
What are the sensor considerations for high temperature flows?
Films cannot be used at high temperatures since they become unstable (resistance changes) are unsuitable for high temperature applications. So, only hot-wires should be used. Since tungsten oxidizes at high temperatures, platinum is recommended (up to 300 C fluid temperature). Even though platinum is resistant to oxidation, it is very weak, and hence, for higher temperature applications (up to 800C sensor temperature), platinum-iridium wires are used.
What does it mean if a unit is temperature compensated?
In a constant flow, the output readings remain constant across a range of temperatures as long as those temperature changes are within the temperature-compensated range.
What does the AccuBalance® Air Capture Hood measure?
The AccuBalance® Air Capture Hood is a flow measuring hood for direct air volume measurements such as from a grille or diffuser.
What does the AccuBalance® Air Capture Hood use for power?
Four C-size alkaline batteries supply power for at least 40 hours of continuous use. When the AccuBalance® Air Capture Hood is first turned on, the percentage of battery life remaining is displayed. To conserve the batteries, the AccuBalance hood will automatically shut itself off if no switches or buttons are pressed for 15 minutes.
What does your two-part accuracy specification actually mean for the AccuBalance® Air Capture Hood?
The accuracy is the sum of the two components of the accuracy spec. Example: The AccuBalance® Air Capture Hood Model 8371 has an accuracy rating of ±5-percent of reading and ±5 CFM. If your AccuBalance hood reads 1,000 CFM, ±5-percent of reading is ±50, plus ±5 CFM for a total tolerance of ±55 CFM. The combined accuracy is 5.5-percent at 1,000 CFM.
What is the accuracy of an AccuBalance® Air Capture Hood?
The accuracy is ±5-percent of reading ±5 CFM (±2.4 l/s, ±8.5 m3/hr).The accuracy is the sum of the two components of the accuracy spec. Example: The AccuBalance® Air Capture Hood has an accuracy rating of ±5-percent of reading and ±5 CFM. If your AccuBalance hood reads 1,000 CFM, ±5-percent of reading is ±50, plus ±5 CFM for a total tolerance of ±55 CFM. The combined accuracy is 5.5-percent at 1,000 CFM.
What is the repeatability of TSI instruments?
The repeatability is included in the accuracy specifications.
What is the typical construction of a hot-film sensor for use in water?
The hot-film sensor for water is similar in construction to that of an air sensor except that an electrically insulating quartz coating replaces the Alumina coating. This is necessary for water and other fluid applications, which are electrically conductive. In addition, probes designed for use in water have all electrically conductive surfaces (needles, solder joints) coated with a red material which provides electrical insulation for all portions of the probe except the sensor element.
What is the typical construction of a hot-wire sensor?
A hot-wire sensor is a small-diameter, solid metallic cylinder, usually made of tungsten, platinum, or platinum-iridium. The typical diameter is approximately 4 microns (0.00015 inch) with a length of 1 to 2 mm. The ends of the wire are copper plated.
What range of flow can it measure?
The flow range for the AccuBalance® Air Capture Hood Models 8371, 8372 and 8373 is from 30 to 2,000 SCFM (15 to 1,000 l/s, 55 to 3,500 m3/hr).
What temperatures can it be used in?
The AccuBalance® Air Capture Hood can be used from 32° to 140°F (0° to 60°C).
What type of calibration facility is used at TSI to calibrate instruments?
TSI calibrates in wind tunnels that have been verified with a Laser Doppler Velocimeter for accuracy. This is the same technique used by NIST for their low-velocity calibration facilities.
When are cylindrical hot-film sensors recommended for use?
Film sensors are sturdier than wires, so they are used in fluids that contain some particles. The other advantage of films over wires is that they retain their calibration better. This is due in part because hot-film sensors are larger and, thus, inherently less prone to and less affected by fouling from particles present in the fluid.
When are hot-wire sensors recommended for use?
Wire sensors are used for applications in air and other electrically non-conducting fluids. The fluid should be clean (free of dirt particles) and filtered. Wires are also used when spatial resolution is important, because they are at least an order of magnitude smaller than films. Spatial resolution becomes important in flows with steep velocity gradients.
When using the AccuBalance® Air Capture Hood, do you need to correct for altitude?
All current AccuBalance® Air Capture Hood Models 8371, 8372 and 8373 have the capability to do the conversion from standard to actual. With Models 8371 and 8372, the user must enter temperature and barometric pressure. The Model 8373 will measure these for you in addition to the calculations.
When using the AccuBalance® Air Capture Hood, do you need to correct for temperature?
The AccuBalance® Air Capture Hood is temperature-compensated, so there is no need to correct for temperature. The AccuBalance hood must be used within the operating temperature range of 32 to 140°F (0° to 60°C) to assure maximum accuracy.
Why are the ends of the hot-wire sensor plated?
There are three main reasons for plating the hot-wires: 1) Plating isolates the sensing portion from the support needles. This defines the sensing area better and reduces flow interference from the needles. 2) Plating reduces the heat conducted from the sensor to the support needles. 3) Plating results in a more uniform temperature distribution along the sensor length.
Why do I have to select supply or return during my measurement?
All AccuBalance® Air Capture Hood Models are designed to accurately measure air flow in either direction through the hood. However, they are not designed to tell which direction the air is flowing. For the highest accuracy, each AccuBalance hood is calibrated twice with flows in each direction. So, to attain the highest accuracy, it's best to select. Model 8373 will automatically sense air flow direction.
Why doesn't TSI's instrument agree with my other instruments?
There are several reasons one instrument may not agree with another.There are differences in how a manufacturer calibrates its own calibration facility. TSI's calibration facility is calibrated with laser velocimetry, which is the same technique used at NIST.While comparing instruments, it is critical to measure in exactly the same location. Sensors placed side-by-side may not read the same, due to flow differences rather than instrument errors.The length of time since the instruments were last cleaned and calibrated can affect their readings.There are different technologies used to measure air velocities: hot-wire, rotary vane, Pitot tube, etc. TSI uses hot wire technology which measures mass air flow.The standard conditions an instrument is calibrated to vary from one manufacturer to another. TSI's standard conditions are 70°F (21.1°C) and 14.7 P.S.I.A. (101.4 kPa).To further discuss instrument discrepancies, please contact a TSI Applications Engineer at (800) 874-2811.