[Irish_Steve]

Hoping to start assembly of my station shortly, and I had a flyer mail in from one of my suppliers this week, and an item on it caught my attention. IF I am reading the information correctly, it is a contactless sensor, with unrestricted rotation capability, and a good resolution, which I think would be suitable for use in the wind direction sensor. It's not cheap, but given that it will be outdoors and not readily accessible due to being at the top of a long pole, I want to use something with better resolution and reliability than that of the Fine Offset unit

Can anyone comment if a AMS22B5A1BHASL136N-ND sensor, available from (among others ) digikey, would be suitable for the purpose? My plan would be to modify a Fine Offset wind direction sensor to remove the existing internal works, and replace it with the Bourns unit, with appropriate modifications to deal with the requirement for a third wire for the connections.

A link to the datasheet is here

Thanks

Steve

[JT118]

Is it the same spec as this? If so it should work. However it would appear from the spec sheet that there is a 10 degree "dead" space, 0-10. Worse than many potentiometer vanes which normally have only a few degrees dead either side of North.

http://www.inspeed.com/wind_speed_direction/Vane.asp
The Inspeed is supported in Weatherduino.

See here for discussion.

http://www.meteocercal.info/forum/Thread...Davis+wind.

Worth considering, given the price of the Bourns sensor. This is a research quality vane used on wind farm assessments.

http://www.ebay.co.uk/itm/332153845172?_...EBIDX%3AIT

[AllyCat]

Hi,

I can't get the full datasheet to download, but the way that I read the (Digikey) specification is that it has "endstops" at 10 degrees and 360 degrees, so would be useless in a wind vane.  I believe the "Continuous" refers to the "infinite" (analogue) resolution between those endstops, i.e. dependent on the resolution of the (external) ADC, or ultimately the noise level of any of the electronic components in the system.   Not in the way the term is used in model makers' "continuous rotation servos".

Of course it is possible to make (or buy) a sensor which measures the (signed) X and Y (i.e. Easting and Northing) magnetic field strengths from a strong rotating "bar" magnet and calculates a direction (see the "ATAN2" function), but I suspect that calibration (in the influence of the Earth's magnetic field) may be an issue. There are lots of different approaches to measuring the wind direction, which rather suggests that there is no easy or perfect solution.  

Cheers,  Alan.

[g0rsq]

Hi,

I can't get the full datasheet to download, but the way that I read the (Digikey) specification is that it has "endstops" at 10 degrees and 360 degrees, so would be useless in a wind vane.  I believe the "Continuous" refers to the "infinite" (analogue) resolution between those endstops, i.e. dependent on the resolution of the (external) ADC, or ultimately the noise level of any of the electronic components in the system.   Not in the way the term is used in model makers' "continuous rotation servos".

Of course it is possible to make (or buy) a sensor which measures the (signed) X and Y (i.e. Easting and Northing) magnetic field strengths from a strong rotating "bar" magnet and calculates a direction (see the "ATAN2" function), but I suspect that calibration (in the influence of the Earth's magnetic field) may be an issue.  There are lots of different approaches to measuring the wind direction, which rather suggests that there is no easy or perfect solution.  

Cheers,  Alan.

I have read the spec sheet, and it looks to be perfectly usable!

AMS22B5A1BHASL136N

AM       Analog Magnetic
S         Single turn
22       22mm
B         1/4" shaft
5          5 Volt
A1       12bit resolution
B         0.5% linearity
H         200uS processing speed
A         1-99% of supply voltages as output voltage
S         Slotted Shaft
L         Axial
1         Output volts increase in CW direction of rotation
36       electrical angle is 360 deg
N         Continuous rotation, no hard stop


4096 points digital resolution gives 11.3 voltage points for each degree of rotation

I might give this a look, as I find the fineoffset a bit of a compromise.

Peter

[AllyCat]

Hi,

Ah yes, I still can't download the datasheet.PDF (which seems to be linking directly to Bourns) but I now see a vital "comma", so what the brief specification says is "Rotation Angle : Electrical : 10 - 360 degrees , Mechanical : Continuous".  But, as previously said, I do wonder about that missing 0 - 10 degrees (electrical). Is it just a "bug" in Digikey's database ?

Also, note the OP part number has a suffix -ND and the correponding specification says "Counterclockwise Increase" which is probably better avoided (unless mounting the vane below the sensor).

Cheers,  Alan.

[Irish_Steve]

The impression I got from the spec sheet was that the rotation change of voltage was based on the view from behind the body, not from the shaft direction, so below the pot, and if that's the case, then I do want it to increase with counter clockwise rotation when seen from below.

I've just looked at the sheet again , the link was digikey's site, try Here

It looks like I was wrong, the spec sheet needs to be looked at very carefully, their orientation IS based on the shaft rotation direction, so shows clockwise on the diagram in an anticlockwise position from below, if that makes sense.

I've had a rotten cold the last few days, so the brain is full of cotton wool right now, and thinking about anything for more than a few minutes isn't working well.

If the resolution is within 10 degrees, that's way better than anything I can get from the Fine Offset device, and close enough for the sort of reporting I am looking for,  and I think that it's a lot tighter than that for this device.

What's making this appealing is that if it's under a good protective shroud so that the bearings are not getting water in to them, the life of this sensor should be very long indeed, and it won't put significant load on the wind vane, which is what's needed in this application.

Thanks all for the feedback, I think it's worth having a go with one of these.

[g0rsq]

The impression I got from the spec sheet was that the rotation change of voltage was based on the view from behind the body, not from the shaft direction, so below the pot, and if that's the case, then I do want it to increase with counter clockwise rotation when seen from below.

I've just looked at the sheet again , the link was digikey's site, try Here

It looks like I was wrong, the spec sheet needs to be looked at very carefully, their orientation IS based on the shaft rotation direction, so shows clockwise on the diagram in an anticlockwise position from below, if that makes sense.

I've had a rotten cold the last few days, so the brain is full of cotton wool right now, and thinking about anything for more than a few minutes isn't working well.

If the resolution is within 10 degrees, that's way better than anything I can get from the Fine Offset device, and close enough for the sort of reporting I am looking for,  and I think that it's a lot tighter than that for this device.

What's making this appealing is that if it's under a good protective shroud so that the bearings are not getting water in to them, the life of this sensor should be very long indeed, and it won't put significant load on the wind vane,  which is what's needed in this application.

Thanks all for the feedback, I think it's worth having a go with one of these.

Resolution is 1/10th of a degree. Output is 12bit resolution analogue output 0-5V (0-5V in 4096 steps)

It is continuous rotation, no stops

Angle of specified component (AMS22B5A1BHASL136N) is 0-360 deg, no gaps

the 10 degree which is confusing is a "programmable" electrical angle, you select the angle you need in 10 deg steps (between 10deg and 360deg) when ordering. ie select the one with 360 deg electrical angle (that is the "36" in the part number). a 10 deg electrical angel will give 0-5 volts out over first 10 deg, then 0-5V from 10deg to 20 deg, then 0-10V from 20deg to 30deg etc.

The 2nd "1" in the part number designates volts increase with counterclockwise movement as viewed from underneath (terminal end)

The "-ND" has no meaning in the specification of the transducer.

See my part number explanation above!


Alternative data sheet here

Try going directly to Bourns and ask for a sample, always worth a try especially if you can use a business address

peter