Benefits of Ultrasonic Anemometers
Ultrasonic anemometers are the high tech alternative to mechanical cup and vane sensors for measuring wind speed and direction
The other advantages . . .
All ultrasonic anemometers provide the following advantages over mechanical sensors:
- no moving parts
- no maintenance requirements
- excellent error accuracy
- easy interface / connection to existing systems
(digital and analogue outputs available)
- automatic, averaged or polled data output
 In addition the 2-axis Wind Horizon and the 3-axis Wind Professional / Wind Research sensors are unique amongst ultrasonic anemometers in that they have a combination of eight further feaures / characteristics which provide real benefits over traditional ultrasonic anemometers:
1. The sensors perform real-time data quality checks
which means that you can have the utmost confidence in your measurements.
Each instantaneous measurement is checked and the result recorded in the output data string as a percentage of reliability (i.e. 100% would indicate that you can have total confidence in the measurement whereas 80% would suggest that an external or environmental influence is affecting measurement accuracy and you should be aware of this).
The validity of each measurement is checked on 3 levels:
Sonic Temperature check
The sensors make measurements on three non-orthogonal paths including the sonic temperature of each path. These sonic temperature path lengths are known and the electronics perform a data quality check by comparing the known length to the measured length. The sonic temperature should not deviate more than a certain percentage on any single path and if a deviation is recorded above the tolerance it is output to the user so corrective action can be taken (ie a recalibration).
Sonic data check
The sensor electronics measure the amount of sonic pulses that are received and compare those to the transmitted pulses. A ratio is derived from this and the percentage output for the user to see. This allows the user to understand how well the sensor is performing in any given condition and take appropriate actions (ie switch heating on, perform instrument checks etc).
Standard deviation check
The sensor electronics perform continuous data quality evaluations on the measured parameters and have a user definable threshold for the standard deviation tolerance that is allowable. For example if you are measuring a 5 m/s wind and have set a standard deviation tolerance of 10% and the sensor suddenly starts to measure 15 m/s then the sensor will output the data as erroneous saving you post processing time while giving you confidence in the data that has been collected.
These are the only ultrasonic anemometers which provide these data quality checks.
Top of page
2. The data output from these sensors is time and date stamped
which means that you do not need to have any additional data loggers or other expensive equipment.
A date and time stamp is very useful when performing several different measurements of different parameters, which may involving multiple instruments and time keeping devices. Having a properly adjusted and accurate date time stamp allows far simpler post processing (if indeed any is needed at all) of the data to collate all the parameters for a given measurement campaign.
There are 3 user adjustable date time settings that are available with these ultrasonics:
The internal clock
The on-board electronics of these ultrasonic anemometers come with a dedicated internal clock. This clock can be adjusted by the user and used as a primary date time stamp clock.
The computer clock
If preferred the anemometers can be set to use the clock of a connected PC or other controlling equipment instead of the internal clock.
The time zone adjustment
The Metek ultrasonics are able to use either local or user definable time zones and headings (for example if your computers local time is 10.23.59 but you would prefer to have the date time stamp in GMT this can be adjusted and output with each string).
Top of page
3. The sensors have a field calibration kit (optional for 2-axis models)
so can do your own confidence checks to reassure yourself that the sensor is functioning accurately.
In the tradition of providing the end user with a complete system which requires as little service or repair work as possible (and where possible can be done by the user themselves) Metek are unique by providing an optional field calibration kit (included as standard with most 3-axis models / configurations).
The field calibration kit allows the user to quickly and easily perform not only a user confidence check of the sensor but also to recalibrate should this be necessary. Within 15 minutes the user can check and perform a calibration in-situ with no extra tools needed.
This can be an immense time and money saver especially during expensive campaigns away from the users base. What this also means is that after the purchase of a Metek ultrasonic anemometer the user can enjoy a lifetime of use without the product ever needing to be returned to Metek unless there has been some mechanical damage or an upgrade is desired.
Typically factory calibrations can cost up to several hundred dollars, without shipping costs, every 2 - 3 years and cause operational delays. With the Metek ultrasonic this is now a thing of the past.
Top of page
4. The sensors have protected transducers
housed within the stainless steel body so they cannot be damaged by animals or environmental conditions.
Typically most ultrasonic anemometers have a thin rubber or similar housing material that protects the transducer while still allowing a known transfer speed of the ultrasonic pulse. These Metek ultrasonic anemometers are designed to work in any environment and are built to a higher standard using only metallic protective faces on all of the transducers.
This is especially important where there are high animal or bird concentrations (birds may peck at the transducers mistaking them for berries etc) or in extremely corrosive environments (such as salt from sea spray). Such conditions can have adverse effects on traditional ultrasonic anemometers and under these conditions users have had to typically have sensors maintained or repaired every 9 months to 1 year. As the Metek ultrasonic anemometers have protective metal transducer faces users can enjoy the full lifetime of the product without any maintenance or repairs due to this classic problem.
It is important to note that the measurement speed of the anemometer is in no way impeded by this design and has been tested over several years around the world.
Top of page
5. The sensors use improved, innovative heating technology
which means that the sensor can be effectively heated using relatively low power.
Metek ultrasonics are truly unique in that they are heated very efficiently while still keeping power requirements within reason.
The 3-axis ultrasonic anemometers from Metek are the first and remain the only 3-axis ultrasonic that is heated. This is due to the unique design with a single central spar for effective routing of the heating elements to the transducer area. Not only is a single central spar effective for the heating but it also provides a known and very small sensor design mechanical error contribution far below conventional designs and truly omni-directional for superior measurements regardless of the instrument orientation compared to wind direction.
The key advantage to the heating design of the Metek ultrasonic anemometers is that a very large proportion of the initially produced heating energy is able to be brought to the transducer face quickly and effectively clearing the snow or ice build up. Because of the design the sensor head does not need any dedicated heating in itself but remains free of ice and snow simply from the unique characteristics of the heating concept. What this means for the user is that the heating efficiency is as high as possible while keeping the power requirements down to an absolute minimum simply by good design.
The heating is regulated by temperature and is user selectable for one of three states (always on, always off and temperature controlled).
The Wind Horizon 2-axis ultrasonic anemometers from Metek use the same time proven heating concept above but on a 2-axis head design.
Top of page
6. The sensors are extremely robust
which means they are suitable for use in harsh conditions due to their immensely rugged stainless steel construction.
The Metek range of ultrasonic anemometers are ruggedly constructed with either stainless steel or aluminium housings that are designed to withstand continuous exposure to corrosive or aggressive environments such as those experienced in industrial stack monitoring.
The thickness of the walls and bases as well as the quality of the materials used are truly superior and allow an incredible amount of physical abuse over several years without impeding the performance. For example they are suited for extremely aggressive applications like road tunnels where very strong cleaning agents are sprayed onto the tunnel walls and any associated equipment needs to be able to withstand these cleaning agents without having to be covered up.
The IP rating of the Metek ultrasonic anemometers is industry leading with a minimum of IP 65. The Metek units will give well over a decade of maintenance free and error free measurements especially in coastal conditions with sea spray or dusty conditions in mines etc.
Compared to other anemometers the Metek 2-axis and 3-axis ultrasonic anemometers are designed from the ground up to withstand rough treatment, severe shocks and a lifetime of use in remote locations. To suit this requirement the Metek sensors have the right mix of structural support and mechanical design that reduces the amount of turbulent affects on the measurements.
Top of page
7. The sensors output sonic (virtual) temperature.
Sonic temperature is the ambient temperature minus the impact of relative humidity.
This range of ultrasonic anemometers not only measure but also output the virtual temperature in units Celsius to two decimal places. If the Metek ultrasonic you order also has analogue inputs then by adding a device to measure relative humidity you can then derive the ambient temperature.
The virtual temperature is also used along with the known path lengths of the ultrasonic anemometer to perform one of the 3 data quality checks offered by this range.
Top of page
8. The 3-axis sensors can be customised to suit your requirements
which means that you can have an anemometer built for your application without paying for features which you do not need.
Metek provides several models of ultrasonic anemometers that are specifically configured to suit the majority of application needs and budgets. However we understand that there will always be a need to have a custom designed unit and therefore we offer the ability to build a system based on one of two basic building blocks:
- a 30 Hz maximum output ultrasonic anemometer
(as used in the Wind Professional range)
- a 50 Hz maximum output ultrasonic anemometer
(as used in the Wind Research range)
Nearly all options and accessories can be added to one of these two systems, now or in the future as budget and requirements dictate. The only item that cannot be added at a later date, beyond the basic speed, is the option of heating as this is incorporated in the welded head design.
This is the only range of ultrasonic anemometers which can be customised in this way.
Top of page |
