HOW FAST – ANEMOMETER CALIBRATION ?

[Jon LawesParticipant @jonlawes51698]

The ETPS used to use equipment like this mounted to the top of a 4×4 (a Jeep is the first one I remember, a Nissan Navara later) on tall cross-braced poles mounted on a roof rack. This anemometer combined with a large fluorescent pole allowed them to do rotary wing cross-wind trial flying up and down the runway in close formation with the vehicle giving them a good visual point of reference, and a telemetry uplink of wind speed and direction (cross referred to the vehicle GPS speed) to the recording systems to allow them to collate the data together. However the point of interest here is that the poles were mounted high enough above the vehicle to try to counteract the affect of the airflow displaced by the vehicle. I seem to remember to total height from the floor was more than ten feet, but don't recall exactly. Anyway, this was considered enough separation to be good enough for their needs. So you need a roof-rack and some cross braced poles! And I would use GPS rather than the speedo. If you use a long straight on a calm day you could go in both directions and take an averaged reading over multiple runs.

[Michael GilliganParticipant @michaelgilligan61133]

As ‘Vector Instruments’ seems rather coy about the prices, this site may also be of interest [and justify all the work]:

**LINK**

https://shop.profec-ventus.com/index.php?cat=c20_Sensors—Measurement-Equipment-measurement-equipement.html

MichaelG.

[Nick Clarke 3Participant @nickclarke3]

Just skimmed through 'The Amateur Scientist' and looked at the article on cloud chambers.

While it explained why i could never get a convincing demonstration of a cloud chamber in any of the physics Labs that I taught; the fact that Scientific American magazine would send out a 'speck of radioactive material' through the post on receipt of a stamped addressed envelope is thought provoking!

Edited By Nick Clarke 3 on 25/05/2022 08:37:27

[GeorgineerParticipant @georgineer]

Posted by Nick Clarke 3 on 25/05/2022 08:36:59:

Just skimmed through 'The Amateur Scientist' and looked at the article on cloud chambers.

While it explained why i could never get a convincing demonstration of a cloud chamber in any of the physics Labs that I taught; the fact that Scientific American magazine would send out a 'speck of radioactive material' through the post on receipt of a stamped addressed envelope is thought provoking!

Edited By Nick Clarke 3 on 25/05/2022 08:37:27

If it's natural rock there are probably no regulations to meet.

When I taught Physics I was always amused by the fact that our 'official' sources had to be kept in lead-lined boxes in a locked dungeon and logged in and out, whereas the natural rocks, which were far more active, lived in a cardboard box in the prep room.

George

[Robert Atkinson 2Participant @robertatkinson2]

Posted by noel shelley on 18/02/2022 12:57:08:

Gentlemen, thanks to those who have contributed so far ! The intention was to use plastic floats and on reflection ali rod would make good arms ! Some damping would help to stabilise readings ! Is there any theoretical way to calibrate the instrument or is it down to a still day and mount it on the roof rack,of the car, Knowing the speedo is 2MPH fast. As for hares there's more than a few round here, that's why there's a long barreled full choke 12 bore in the cupboard. When it was given to me I was warned not to shoot at anything I wanted to eat at less than 35yards. The local gun club stopped laughing when one day I used this weapon to stop clay pigeons just before they hit the ground, some considerable distance away ! Noel.

Edited By noel shelley on 18/02/2022 13:01:14

Yes this, but do at least two runs in opposite directions to average out the effect of wind. Don't try to calibrate to any unit at this point just measure the "raw" frequency from the sensor with a frequency counter, digital tachometer readout or similar. Ideally do a range of speeds and plot the results in a graph to see how linear it is. Ideally the graph should be a straight line.

Robert G8RPI

[peak4Participant @peak4]

Noel, I don't know where you live, but your local crane hire company might be worth quizzing.
Even our local market operator has a commercial anemometer to see if it's too windy to fall foul of insurance company guidance when putting the roof tarpaulins on the stalls.

If you're in shouting distance of Buxton, Derbyshire, you can borrow mine for a while.

Bill

[Joseph Noci 1Participant @josephnoci1]

A bit off-beat maybe… I designed an Omni-directional Airspeed sensor (OAS) that sits atop the standpipe above the main rotor on the SAAF Rooivalk 'copter. A 350mm horizontal tube 10mm OD, with pitot holes in the tips at opposing leading edge, feeding two pressure sensors. The tube spins ( like the "copter rotor..) and if standing still with no wind, the differential pressure measurement is nil. Any wind ( from wind or motion) creates differential pressure in a sinusoid voltage, which is proportional to airspeed. A optical encoder disc fixed to the vertical spinning shaft gives position of the spinning tube relative the the sinusoid, and from this is derived wind direction. The device was calibrated in the Wind Tunnel at the CSIR…

I still have the prototype which I use on the ground when we go fly our UAV in the desert – to derive landing approach for wind direction and speed…

Joe

 

EDIT – we had a 20meter rail with a winch towed carriage in the lab – the OAS was mounted to the carriage and the winch would wind the OAS along the track – from 0m/s to 10m/s within 15meters. Carriage speed and OAS data was logged and a calibration curve for the sensor derived. We were generally within 3% of the wind tunnel cal results..Air cons were turned off during the runs…

edit-2 fix a typo or two..

Edited By Joseph Noci 1 on 25/05/2022 20:41:40

[not done it yetParticipant @notdoneityet]

Posted by Georgineer on 25/05/2022 18:09:44:

If it's natural rock there are probably no regulations to meet.

When I taught Physics I was always amused by the fact that our 'official' sources had to be kept in lead-lined boxes in a locked dungeon and logged in and out, whereas the natural rocks, which were far more active, lived in a cardboard box in the prep room.

George

Haha, my Dad’s Avia wristwatch gives more geiger counts than the school radio-isotope samples.

When I worked at what is now Amersham International, I used it to ‘befuddle’ my supervisor – he would search all over my lab coat for some contamination but could never find any. After a while he ignored any counts, when I was checking myself before leaving the building.

[duncan webster 1Participant @duncanwebster1]

Coming out of a building at Sellafield once I set off the hand monitor alarms. Twenty minutes of increasingly aggressive scrubbing didn't help, then I realised that I had a Swatch wrist watch. Took it off and slid it under the barrier, no further problem. Ive also had problems with man made fibre trousers, which seem to attract Radon coming out of the bed rock. Answer to that was to stand out in the wind for a few minutes, alternative would have been a pair of paper trousers supplied by the monitors.

[NealebParticipant @nealeb]

The anemometers fitted to the masthead of small sailing boats used to have the "three cups" style speed measurer together with a vane to give wind direction, both feeding instruments in the cockpit or elsewhere. Some newer systems use just the "three cup" device, but one cup has a notch cut out so that rotation speed varies during each rotation based on wind direction, and clever electronics can use the signals to give both speed and direction from this single sensor. I mention this because it must use a much more sophisticated sensor than the "one pulse per rev" system – doesn't it? Another of those "I wonder how they do that?" questions!

[NealebParticipant @nealeb]

(Double post deleted)

Edited By Nealeb on 26/05/2022 09:41:31

[CirclipParticipant @circlip]

Wireless World did a combined mast head anemometer/wind direction article back in the day and sure that Maplins (RIP) did weather station kits.

Regards Ian.

[Nigel Graham 2Participant @nigelgraham2]

Maplins RIP indeed.

It even sells what it calls "Weather Stations" .

.

It has been restored as "Maplin" – singular – but as only a supermarket retailing ready-made electronic IT equipment, cameras, gadgets, toys and such accessories as cables, batteries and power units.

It does have a range of "hobby" goods but that is little more than toy cars and some odd "kits" of little intrinsic use or worth, probably also aimed at children.

Though I did see the name "Raspberry Pie" and even a soldering-iron listed, so all is not lost for the serious hobby user.

Discrete components though? I searched for resistors and capacitors. "Never 'eard of 'em, Guv! "

Really no better for anyone with a genuine interest in electrical and mechanical engineering, than Currys or Argos, with a web-site to match.

'

Weather Stations though… Yes!

They took a bit of finding and only a few of about 10 products do anything I would describe as weather-station functions. The rest seem only to tell you little more than the temperature and relayed weather-forecasts, for which I've a thermometer and radio.

Unfortunately though for the OP, none of even the more useful ones include wind-speeds.

[noel shelleyParticipant @noelshelley55608]

Gentlemen, 3 months ago I started this thread,Swarfy, yes brass would add mass, Diogenes great idea to involve the pub in the calibration process, Dennis D I have a marine sat nav and a long straight road, Peak 4, NDIY, Dave (SOD), Duncan W, Howard L, Alan C, Joseph Noci 1, and all, I have read your posts and got much interests and knowledge from the ideas. Then out of the blue whilst working with a guy on a cherry picker he pulled out a Anemometer out of his pocket – I can borrow this when the time comes. There is a sailing club near by, but at the foot of a cliff so the readings could be very questionable. Hall effect for speed and also for direction, seems the way I shall go. WHEN I CAN FIND TIME ! Many thanks, I will keep you all posted. Noel.

[Author]

Posts