Author Topic: Calibrate wind direction.  (Read 1511 times)

0 Members and 1 Guest are viewing this topic.

Offline JohnSche

  • Member
  • *
  • Posts: 7
Calibrate wind direction.
« on: August 14, 2022, 07:04:47 PM »
Situation:
Vantage pro vp2
My wind unit is placed on a large pole which is not easily accessible. the pole is not adjusted to the north. But i know exactly in what direction it is pointing.

When I follow the instructions from the manual and given on the internet, the results are terrible and change from time to time. Because I cannot block the vane in an desired position (not reachable) I cannot correct an offset.

Question:
Is there a way to tell to the VP2 that the vane points to 273 degrees, so everything works without the troublesome procedure as given in the manual?

Kind regards,
John Scheepmaker

Offline CW2274

  • Forecaster
  • *****
  • Posts: 6361
    • Conditions @ CW2274 West Tucson-Painted Hills Ranch
Re: Calibrate wind direction.
« Reply #1 on: August 14, 2022, 08:07:19 PM »
Question:
Is there a way to tell to the VP2 that the vane points to 273 degrees, so everything works without the troublesome procedure as given in the manual?
Although it can be a pain to extrapolate, it can be done, but you'll need to use the console or software like Weatherlink. Easiest way is to take your console outside in calm-ish wind and visually watch the vane til the console matches. Since you have the offset, you'll eventually get it sooner than later. 

Offline Mattk

  • Forecaster
  • *****
  • Posts: 1828
Re: Calibrate wind direction.
« Reply #2 on: August 14, 2022, 08:45:09 PM »
If the results of a calibration are changing? then it would appear you are not following the calibration procedure?

As you would know the direction the vane is pointing then the offset can be determined. It makes no difference to what direction is showing on the console, one you gave entered the calibration procedure properly the most right hand digit value showing in the wind rose will be flashing, the whole wind direction value will be frozen and the CAL number will be displayed along the ticker tape.

Use the left/right arrows to select the digit (which will flash) in the wind rose to change up/down to set the number required until the direction in the wind rose is adjusted relative to the offset required. At this point the CAL # will not change. Once changes made then press Done. If you go back into the calibration procedure then the CAL# will be displayed that is offsetting the direction relative to the direction the wind arm is point and North etc.

If you already have a CAL# in the system then reset the CAL# to be zero before applying the offset you require.

Once calibrated the results will match what it has ben told to offset by and the CAL# won't change     

Offline JohnSche

  • Member
  • *
  • Posts: 7
Re: Calibrate wind direction.
« Reply #3 on: August 15, 2022, 03:10:48 PM »
Dear CW2274  and Mattk,

Thank you for your answer. They are not working because my vane moves to much so I don't have a correct direction. It also differs (+ or -) so I get garbage. I'll try to explain better. Please correct me when my assumptions are not correct.

When Davis calculates the wind direction that should be displayed it takes the Van pointing direction and adds this to "point zero" (Default North). In my case "point zero" is, let's say 270 degrees). I think the easiest way to correct this is by telling the VP2 that it should not calculate from "point zero" North but from "point zero" West. All the methods I found on internet are very complicated and give wrong results.

Suppose I take my console outside where I can see my vane. I have to guess the direction and calculate the offset, but while I do this the direction (and the offset) change rapidly (I cannot block the Vane). So at the end the result is always bad.

Offline Mattk

  • Forecaster
  • *****
  • Posts: 1828
Re: Calibrate wind direction.
« Reply #4 on: August 15, 2022, 04:42:37 PM »
There is nothing to guess, no need to take console outside, the offset is fixed from the direction the anemometer arm is pointing and north. Once you enter calibration mode the direction displayed inside the wind rose on the console, apply the known offset to the displayed (frozen) wind direction, then using the arrow keys SET the wind direction value then press Done.

Think about this way. If your anemometer arm is pointing 273 degrees and the wind wane is pointing directly away along the mounting arm then your console would be displaying 0 degrees, North, correct? Using the calibration procedure then you would set the console wind direction (in the wind rose) to be 273 degrees, press Done will set the actual CAL# applied and wind direction would be then relative to actual North.

It does not matter what direction is displayed within the wind rose (in CAL mode), you simply derive the proper direction using the "known" offset and set the displayed wind direction inside the wind rose. This is not overly complicated, not sure why it is being made complicated?       

Offline JohnSche

  • Member
  • *
  • Posts: 7
Re: Calibrate wind direction.
« Reply #5 on: August 15, 2022, 05:05:21 PM »
This is the way I thought (more-or-less) about it some time ago. Probably made some mistakes.
Do you agree that in my situation I should allways, regardless of the value displayed, set the offsett to 273?

Offline Mattk

  • Forecaster
  • *****
  • Posts: 1828
Re: Calibrate wind direction.
« Reply #6 on: August 15, 2022, 05:49:43 PM »
This is the way I thought (more-or-less) about it some time ago. Probably made some mistakes.
Do you agree that in my situation I should allways, regardless of the value displayed, set the offsett to 273?

No your "offset" is essentially the CAL# and this is determined when you set the wind direction and the wind direction you set must be relative to the displayed vane direction during the calibration process

Offline davidmc36

  • He who dies with the most toys wins!
  • Forecaster
  • *****
  • Posts: 1121
  • FN25ie61jw
    • MorewoodW34
Re: Calibrate wind direction.
« Reply #7 on: August 15, 2022, 06:04:27 PM »
Doesn't he just need to get into the adjust section  and reduce the reading by 87 degrees??????

360 minus 273 ????

Offline mcrossley

  • Forecaster
  • *****
  • Posts: 969
    • Wilmslow Astro
Re: Calibrate wind direction.
« Reply #8 on: August 15, 2022, 06:08:07 PM »
Your offset is 273 - 360 = -87 degrees

When you go into calibration...
1. Check the ticker shows "CAL 0" - if not then subtract that CAL value from direction shown, and save it (Done). Then start the process again. You should now have "CAL 0" in the ticker.
2. Subtract 87 from whatever direction is shown, then set the direction to that value.
3. Save this - Done
4. Go back into the calibration setup, you should now have "CAL -87" in the ticker.
5. Exit calibration again - you are finished.
Mark

Offline Mattk

  • Forecaster
  • *****
  • Posts: 1828
Re: Calibrate wind direction.
« Reply #9 on: August 15, 2022, 06:21:35 PM »
Doesn't he just need to get into the adjust section  and reduce the reading by 87 degrees??????

360 minus 273 ????

The console reading is "set" to the direction the wind vane is pointing relative to the mounting arm direction. This determines the CAL# which is then applied to all raw wind directions to provide the actual wind direction relative to North. The 87 degrees is essentially the determined CAL# but is not a value (as such) that can be directly input. 

Back to the example, mounting arm is pointing 273 degrees, wind vane is pointing directly along the mounting arm, pointy end pointing away from pole support, console will be displaying 0 degrees, but the actual direction along the mounting arm and vane is 273 degrees, set the console raw direction to 273 (actual), CAL# will be determined from this.

Now if the raw console reading was 87 degrees then one would set the console direction (as part of the CAL procedure) to 0 degrees   

Offline davidmc36

  • He who dies with the most toys wins!
  • Forecaster
  • *****
  • Posts: 1121
  • FN25ie61jw
    • MorewoodW34
Re: Calibrate wind direction.
« Reply #10 on: August 16, 2022, 12:48:46 AM »
Your offset is 273 - 360 = -87 degrees

When you go into calibration...
1. Check the ticker shows "CAL 0" - if not then subtract that CAL value from direction shown, and save it (Done). Then start the process again. You should now have "CAL 0" in the ticker.
2. Subtract 87 from whatever direction is shown, then set the direction to that value.
3. Save this - Done
4. Go back into the calibration setup, you should now have "CAL -87" in the ticker.
5. Exit calibration again - you are finished.

I see what you are saying here. Go to the CAL section  and first remove any previous adjustments.

Then do the process proper from beginning and input the 87 degrees.

Offline Mattk

  • Forecaster
  • *****
  • Posts: 1828
Re: Calibrate wind direction.
« Reply #11 on: August 16, 2022, 02:38:33 AM »
......Then do the process proper from beginning and input the 87 degrees.

No, the 87 degrees is not what is "input", what is input is the actual bearing in place of the raw bearing, and in this case the computed CAL # will be -87

Offline davidmc36

  • He who dies with the most toys wins!
  • Forecaster
  • *****
  • Posts: 1121
  • FN25ie61jw
    • MorewoodW34
Re: Calibrate wind direction.
« Reply #12 on: August 16, 2022, 05:29:41 AM »
OK Input the 87 degrees. Adjust the bearing by 87 degrees.

Offline Mattk

  • Forecaster
  • *****
  • Posts: 1828
Re: Calibrate wind direction.
« Reply #13 on: August 16, 2022, 06:48:41 AM »
OK Input the 87 degrees. Adjust the bearing by 87 degrees.

Correct, the actual input bearing replaces the raw bearing in the wind rose using the arrow keys. At this point the CAL# will still display 0, pressing [Done] closes calibration mode computing the calibration value and if the Calibration mode is opened again the Ticker tape (in this case) will display CAL -87

Offline JohnSche

  • Member
  • *
  • Posts: 7
Re: Calibrate wind direction.
« Reply #14 on: August 16, 2022, 03:43:43 PM »
After reading your suggestions/explanations I decided to try get thinks running so I cleaned things up.
-   Reset my VP2 (done for 2 secs)
-   Checked position Vane arm (340)

Situation: Almost windless.
Estimated Vane pointing direction: 340

First attemt:
Entered new Cal 97 (340 Ė 245) (also new display value, so wrong)


Second attempt
Entered Cal 245 (Vane arm direction). Result display value 245 (wrong)


Third attempt
Entered Cal 340 This is the result that should be displayed.


So Iím happy everything seems OK now. Thanks to the absence of wind and ?

Because there is no wind at all I cannot check what happens when the direction changes.

I wonder if the Cal 340 would have helped under other circumstances. So Iím still nor sure I understand what happened. 

Offline mcrossley

  • Forecaster
  • *****
  • Posts: 969
    • Wilmslow Astro
Re: Calibrate wind direction.
« Reply #15 on: August 16, 2022, 04:14:00 PM »
I think you may have got there in the end. But I do not think you understand what you are doing or our explanations!  :lol:
Mark

Offline Mattk

  • Forecaster
  • *****
  • Posts: 1828
Re: Calibrate wind direction.
« Reply #16 on: August 16, 2022, 04:44:54 PM »
If as per the original post the mounting arm is pointing 273 degrees then I don't believe there is an understanding of what is required based on the first, second, third attempt etc.

Why the "estimation" of the vane pointing direction (340)? The only relevant direction value is what is displayed inside the wind rose during the calibration procedure.

It also appears the first, second, third attempt etc was using previously attempts CAL# in the system which would be very confusing?

So No I don't believe it is ok? 

Offline JohnSche

  • Member
  • *
  • Posts: 7
Re: Calibrate wind direction.
« Reply #17 on: August 16, 2022, 05:05:15 PM »
OK, let's try an example (if you want).
When I enter Cal# mode I see several values.

For example in the Rose I see 250, what does this mean?

From this same value a digit is blinking

To know the correction factor I need to now the difference between the displayed value and the actual Vane direction?

How do I get the actual Vane direction?


Offline Mattk

  • Forecaster
  • *****
  • Posts: 1828
Re: Calibrate wind direction.
« Reply #18 on: August 16, 2022, 06:19:06 PM »
Quote
....For example in the Rose I see 250, what does this mean?....

Assuming the CAL# setting is 0 (zero) 250 is the raw wind direction indication based on the direction the wind vane is pointing relative to the direction the mounting is pointing. I am assuming the wind direction shaft of this anemometer has a "D" shaft which forces the wind vane to fit on the shaft in one position only? This essentially fixes 0 degrees to be the direction the mounting arm is pointing.

Now based on the initial post and mention that the mounting arm is pointing 273 degrees but the console (with zero CAL#) thinks the direction the mounting arm is pointing is north (0 degrees) and the wind vane is @ 250 degrees which in real terms is 163 degrees which 273+250=523-360=163 degrees or knowing the mounting arm is pointing 273 degrees, 87 degrees west of north then the same thing is 250-87=163 degrees

Now your raw wind rose display is 250 degrees which is 163 degrees actual wind direction relative to north (proper)

Quote
.... From this same value a digit is blinking....

Ok so the digit that should be blinking is normally the right most digit but using the left/right arrow keys you can select either the 2 or 5 or 0, which ever digit is blinking then change the required digit using the Up/down arrows.

With 25[0] zero blinking using the up/down arrow keys change the digit to 3, left arrow and 5 will blink, use up/down arrows change digit to 6, left arrow and change digit to 1, CAL in ticker tape will still show 0, press [Done] and you are done.

If you go back into Cal mode the ticker tape will display CAL -87

Quote
.... How do I get the actual Vane direction? ....
Hopefully explained above
 
« Last Edit: August 16, 2022, 06:21:00 PM by Mattk »

Offline davidmc36

  • He who dies with the most toys wins!
  • Forecaster
  • *****
  • Posts: 1121
  • FN25ie61jw
    • MorewoodW34
Re: Calibrate wind direction.
« Reply #19 on: August 16, 2022, 07:39:18 PM »
OK, let's try an example (if you want).
When I enter Cal# mode I see several values.

For example in the Rose I see 250, what does this mean?

From this same value a digit is blinking

To know the correction factor I need to now the difference between the displayed value and the actual Vane direction?

How do I get the actual Vane direction?

No. You do not need to know anything besides what you already know. It is off by 87 degrees, according to your original statement. So WHATEVER it displays when ready to calibrate........alter it by 87 degrees.....DONE.

Offline JohnSche

  • Member
  • *
  • Posts: 7
Re: Calibrate wind direction.
« Reply #20 on: August 17, 2022, 05:36:44 AM »
OK Input the 87 degrees. Adjust the bearing by 87 degrees.

At this moment I realized that my offset should be subtracted (or added) from/to the reading. This explains all the strange readings. I have been in this tunnel for a long time. Especially the strike-through was a wake-up call. Thanks.

Offline JohnSche

  • Member
  • *
  • Posts: 7
Re: Calibrate wind direction.
« Reply #21 on: August 17, 2022, 07:01:15 AM »
Quote
....For example in the Rose I see 250, what does this mean?....

Assuming the CAL# setting is 0 (zero) 250 is the raw wind direction indication based on the direction the wind vane is pointing relative to the direction the mounting is pointing. I am assuming the wind direction shaft of this anemometer has a "D" shaft which forces the wind vane to fit on the shaft in one position only? This essentially fixes 0 degrees to be the direction the mounting arm is pointing.

Now based on the initial post and mention that the mounting arm is pointing 273 degrees but the console (with zero CAL#) thinks the direction the mounting arm is pointing is north (0 degrees) and the wind vane is @ 250 degrees which in real terms is 163 degrees which 273+250=523-360=163 degrees or knowing the mounting arm is pointing 273 degrees, 87 degrees west of north then the same thing is 250-87=163 degrees

Now your raw wind rose display is 250 degrees which is 163 degrees actual wind direction relative to north (proper)

This made me understand the logic. I allways thought that when I told VP2 the offset  it would calculate all necessary values. Wrong

Quote
.... From this same value a digit is blinking....

Ok so the digit that should be blinking is normally the right most digit but using the left/right arrow keys you can select either the 2 or 5 or 0, which ever digit is blinking then change the required digit using the Up/down arrows.

With 25[0] zero blinking using the up/down arrow keys change the digit to 3, left arrow and 5 will blink, use up/down arrows change digit to 6, left arrow and change digit to 1, CAL in ticker tape will still show 0, press [Done] and you are done.

If you go back into Cal mode the ticker tape will display CAL -87

Quote
.... How do I get the actual Vane direction? ....
Hopefully explained above