Can a customer recalibrate his/her own unit?
Yes and no. When the unit is calibrated, an EEPROM is programmed with the calibration data. A customer cannot do a full calibration in the field. However, a field calibration adjustment is possible through the software. Again, this is not a full calibration. TSI recommends a full annual calibration. See Application Note TI-112 for details.
Can portable air velocity meters use rechargeable batteries?
You can use rechargeable batteries in all of the portables except for the Model 8340 NOTE: Rechargeable batteries will nullify the intrinsic safety rating on the Model 8340. Also, rechargeable batteries don't last as long as alkaline batteries.
Can the VelociCalc® and VelociCheck® instruments read to zero ft/min?
The low end of the velocity specification for the VelociCalc® meters is 30 ft/min (0.15 m/s). The units will read air velocities between zero and the minimum specified, however, the accuracy is uncertain.
Can the VelociCheck® instruments read to zero ft/min?
The minimum velocity specification on VelociCheck® meters is to 25 ft/min (0.13 m/s), and on the VelociCalc® meters to 30 ft/min (0.15 m/s). The units will read air velocities between zero and the minimum specified, however, the accuracy is uncertain.
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.
How does the 8340 differ from other VelociCheck® Meters and VelociCalc® Meters?
The 8340 was designed specifically to be intrinsically safe. It is NOT just a specially tested VelociCheck® meter. There are many electronics design features which are necessary to meet the safety requirements. For example, all electronic circuits are designed so that a component failure cannot result in high electrical current and, in turn, "hot spots" in the instrument. The most obvious external difference is the sensor element itself. While all other TSI hand-held instruments use a robust ceramic or metal-clad sensor element, the 8340 uses a tiny thermistor as its sensor. This tiny thermistor operates at a very low current and will therefore not become dangerously hot even if its control circuits fail. Another obvious difference is that the 8340 is only available with a short, retractable probe. The popular coiled cord used on the Model 8330 VelociCheck meter and all models of the VelociCalc® meter cannot be made intrinsically safe. If the cable were cut, excessive current could result in hot spots. Regrettably this makes the 8340 less convenient to use than some of our other instruments. A good feature of the 8340 is long battery life. Due to the low power sensor element, batteries in the 8340 typically last 20 hours. In contrast, the 8330 with its conventional sensor has a typical battery life of 10 hours.
How has the 8340 been certified in the US? Outside of the US?
The 8340 was tested and accepted for use in hazardous locations by Underwriters Laboratories, Inc. (UL™ test file number E126398, Project 90NK16758, October 23, 1990). This acceptance involved evaluation of the circuit design as well as certification testing of the product itself.The 8340 has been accepted for use in the following categories:Class I, Groups C and DClass II, Groups E, F, and GClass IIINote that the UL™ acceptance specifically requires the use of ALKALINE BATTERIES. It is NOT SAFE to use Nickel Cadmium batteries in the 8340 because NiCd batteries are capable of extremely high short circuit currents. In the event of a circuit failure, NiCd batteries could generate dangerously high temperatures in electronic components.CERTIFICATION OUTSIDE OF THE US: At this time (September 1994) the model 8340 is only certified by UL™ in the US. The UL™ certification is accepted outside of the US by some governments and by some customers. In some cases the UL™ test report will help to make the 8340 acceptable to customers outside of the US A copy of this UL™ test report is available from TSI on request.
How long is the warranty period for the portable air velocity meters?
The portable air velocity meters all have a two-year warranty. See the instruction manual for details.
How often should I recalibrate my Portable Air Velocity Meter?
To maintain a high degree of accuracy in your measurements, TSI recommends that you return your instrument to the factory for an annual NIST traceable recalibration.
Is the VelociCheck CE approved?
Most of TSI's line of instruments are CE approved including the Model 8330. The only exception is that the Model 8340 is not CE approved and is not available in countries with CE requirements.
Is there a more rugged version for operating in dirty environments -- in exhaust stacks, chemical acid baths, etc.?
The portable air velocity meters are designed to operate in clean environments. If used in a dirty environment, dirt will collect on the sensor and change the calibration. Corrosive environments will damage the sensor.
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 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 do all of those certification categories mean in the US, Canada, and the rest of the world?
Instruments can be designed and certified to be safe in different classifications of gasses, vapors, and dusts. Gas classifications which are more easily ignited require different electronic designs for the instrument. The model 8340 has been tested and certified to be safe in all categories EXCEPT acetylene and hydrogen. See the table in the INTECH article for more information. This gives US/Canadian classifications and their IEC counterparts.
What do the slow-fast response buttons on the VelociCheck® Meters 8330 and 8340 actually do?
This feature allows you to change the display dampening to either a 3 or 12-second average. The display will update velocity readings every second. The displayed values are a moving average or running average of the measured velocity. If velocity readings are changing too quickly, select the slow response option to reduce the display fluctuation.
What does "Intrinsically Safe" mean?
An "intrinsically safe" instrument has been specially designed to be safe when used in hazardous locations. Hazardous locations are areas where flammable or explosive gasses are or can be present. The instrument must provide no exposed ignition source in normal operation. In addition, it must be designed so that internal failures in the instrument cannot cause dangerous "hot spots".
What does your two-part accuracy specification tell me for the VelociCalc® Air Velocity Meter and VelociCheck® Comput Air Velocity Meter?
The accuracy is the greater of the two components of the accuracy specification. Example: The VelociCalc® Plus Air Velocity Meter Model 8386 has an accuracy rating of ±3 percent of reading or 3 ft/min, whichever is greater. If your VelociCalc Plus meter reads 1,000 ft/min, ±3 percent of reading is ±30 ft/min. Since this is larger than ±3 ft/min, the accuracy specification at 1000 ft/min is ±30 ft/min.
What is considered a high velocity?
Any velocity over 1,000 ft/min.
What is the repeatability of TSI instruments?
The repeatability is included in the accuracy specifications.
What standards do the portable air velocity meters comply with?
Units are supplied with a certificate of calibration traceable to the National Institute of Standards and Technology (NIST NOTE: Rechargeable batteries will nullify the intrinsic safety rating on the Model 8340. Also, rechargeable batteries don't last as long as alkaline batteries.
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.
What type of special versions are available for portable air velocity meters?
The family of portable air velocity meters offers a wide variety of features and ranges to meet the needs of most applications; therefore, no special versions are available.
Who are the potential customers for this product?
In general, anyone needing to make air velocity measurements in the presence of or vicinity of the rated hazardous environments would be a potential customer.Oil drilling and refining Chemical factories Insurance company and government field personnel who evaluate and inspect operations at their clients' facilities. Examples are laboratories with fume hoods or chemical processes that require ventilation. Industrial hygienists in companies that handle or work with hazardous materials. Safety officers in plants that use or process the rated hazardous materials (ethylene, propane, metal or carbon dusts, suspended combustible fibers).
Why aren't the probes field replaceable?
Replacing a probe requires calibration, temperature compensation, replacing resistors, etc. Very few customers have the capability to do these operations.
Why can't I read velocity and temperature at the same time?
On the VelociCalc® Plus Meter models you can read velocity and temperature at the same time. Temperature displays in the upper left corner of the display while the velocity displays in larger size on the lower half of the display. However, on earlier Models, the thermal anemometer and the temperature sensor were placed within close proximity and the thermal anemometer affected the temperature of the surrounding air. When velocity is being taken, temperature readings read too high. With the VelociCalc Plus meter, the temperature sensor is placed further away from the thermal anemometer to avoid this phenomenon.
Why do the readings fluctuate?
The pressure sensor in our micromanometers responds quickly to changes. The fluctuating readings you see are actually variations in the pressure. To reduce the fluctuation, select a longer time constant to dampen the display or move the sensor into a less turbulent area.