Author Topic: rainfall offset.  (Read 1439 times)

0 Members and 1 Guest are viewing this topic.

Offline mkutche

  • Forecaster
  • *****
  • Posts: 1031
    • GosportWx.com
rainfall offset.
« on: February 25, 2023, 02:12:19 PM »
I had to get a new rain gauge and when it tips it reads 0.04" per tip unlike my other one was 0.01" per tip what would the rainfall offset be? I'm not good at math lol

Thanks
Mike
Mike K.
Davis Vantage Vue 6250 - CumulusMX (3.21.1-b3205)
Gosport, Indiana
Gosportwx.com twitter.com/GosportINWX
-----------------------------------------------------------

Offline mkutche

  • Forecaster
  • *****
  • Posts: 1031
    • GosportWx.com
Re: rainfall offset.
« Reply #1 on: February 26, 2023, 07:25:15 PM »
bump
Mike K.
Davis Vantage Vue 6250 - CumulusMX (3.21.1-b3205)
Gosport, Indiana
Gosportwx.com twitter.com/GosportINWX
-----------------------------------------------------------

Online Mattk

  • Forecaster
  • *****
  • Posts: 2005
Re: rainfall offset.
« Reply #2 on: February 26, 2023, 09:33:40 PM »
It is not an offset (as such) but a factor, factor of 4 (400%)

Strange capacity @ 0.04" per tip? So 25 tips to the inch

Offline SnowHiker

  • Forecaster
  • *****
  • Posts: 352
Re: rainfall offset.
« Reply #3 on: February 27, 2023, 01:00:44 PM »
Strange capacity @ 0.04" per tip? So 25 tips to the inch

Basically it's metric, 1mm.  I've seen cheaper stations like Oregon Scientific that use that resolution rain gauge.

Offline mcrossley

  • Forecaster
  • *****
  • Posts: 1062
    • Wilmslow Astro
Re: rainfall offset.
« Reply #4 on: February 27, 2023, 01:56:13 PM »
So mm to inches you divide by 25.4 = 0.03937

1 mm is a big tip size though!
Mark

Offline mkutche

  • Forecaster
  • *****
  • Posts: 1031
    • GosportWx.com
Re: rainfall offset.
« Reply #5 on: February 27, 2023, 05:01:05 PM »
would that be the multiplier?
Mike K.
Davis Vantage Vue 6250 - CumulusMX (3.21.1-b3205)
Gosport, Indiana
Gosportwx.com twitter.com/GosportINWX
-----------------------------------------------------------

Online Mattk

  • Forecaster
  • *****
  • Posts: 2005
Re: rainfall offset.
« Reply #6 on: February 27, 2023, 05:07:55 PM »
would that be the multiplier?

Yes, For every tip is 0.04" (1.016mm) for a system expecting 0.01" (0.254mm) so multiple *4, note the mm converson is not exactly 1mm but probably well within design spec. Does your system have an option to set a 1mm gauge?

Offline mkutche

  • Forecaster
  • *****
  • Posts: 1031
    • GosportWx.com
Re: rainfall offset.
« Reply #7 on: February 27, 2023, 05:08:51 PM »
would that be the multiplier?

Yes, For every tip is 0.04" (1.016mm) for a system expecting 0.01" (0.254mm) so multiple *4, note the mm converson is not exactly 1mm but probably well within design spec. Does your system have an option to set a 1mm gauge?

i don't see it in the settings anywhere sadly
Mike K.
Davis Vantage Vue 6250 - CumulusMX (3.21.1-b3205)
Gosport, Indiana
Gosportwx.com twitter.com/GosportINWX
-----------------------------------------------------------

Offline mkutche

  • Forecaster
  • *****
  • Posts: 1031
    • GosportWx.com
Re: rainfall offset.
« Reply #8 on: February 27, 2023, 05:10:33 PM »
would that be the multiplier?

Yes, For every tip is 0.04" (1.016mm) for a system expecting 0.01" (0.254mm) so multiple *4, note the mm converson is not exactly 1mm but probably well within design spec. Does your system have an option to set a 1mm gauge?

i don't see it in the settings anywhere sadly

see image https://prnt.sc/7H_LHrI9sCGw
Mike K.
Davis Vantage Vue 6250 - CumulusMX (3.21.1-b3205)
Gosport, Indiana
Gosportwx.com twitter.com/GosportINWX
-----------------------------------------------------------

Offline SnowHiker

  • Forecaster
  • *****
  • Posts: 352
Re: rainfall offset.
« Reply #9 on: February 27, 2023, 05:14:56 PM »
1 mm is a big tip size though!

Yes it is.  However the purpose of the metric system is to keep things in even multiples of 10, other fractions confuse the matter, and 0.1mm (100Ám or 0.004") is getting a little impractical to measure with a regular tipping rain gauge, so therefore you're stuck with one millimeter.

 ](*,)  (emoticon of a metric system user banging his head against a ruler measured in fractions of inches)

 :grin:

Offline mcrossley

  • Forecaster
  • *****
  • Posts: 1062
    • Wilmslow Astro
Re: rainfall offset.
« Reply #10 on: February 27, 2023, 05:19:44 PM »
EDITED: I misread your original post as having an original tip size of 0.001 inches!

I don't think so  You don't say which station you have. But if the station is expecting 0.01 in per tip, but it is now registering 1 mm per tip (are you *really* sure it is 1 mm, not 0.1 mm?), Then ideally you need to do the correction in the station itself. Or at least some of the correction.

If all the correction is being done in CMX, then the multiplier would be 3.937008.




In this part of the world a 1mm per tip sensor would not register any rain on many days it rained less than 1 mm.
« Last Edit: February 27, 2023, 05:47:42 PM by mcrossley »
Mark

Offline mkutche

  • Forecaster
  • *****
  • Posts: 1031
    • GosportWx.com
Re: rainfall offset.
« Reply #11 on: February 27, 2023, 05:29:02 PM »
I don't think so  You don't say which station you have. But if the station is expecting 0.001 in per tip, but it is now registering 1 mm per tip (are you *really* sure it is 1 mm, not 0.1 mm?), Then ideally you need to do the correction in the station itself. Or at least some of the correction.

If all the correction is being done in CMX, then the multiplier would be 39.37008.

That is the new tipper is almost 40x less sensitive than the one you had before!


In this part of the world a 1mm per tip sensor would not register any rain on many days it rained less than 1 mm.

WS-2080
Mike K.
Davis Vantage Vue 6250 - CumulusMX (3.21.1-b3205)
Gosport, Indiana
Gosportwx.com twitter.com/GosportINWX
-----------------------------------------------------------

Offline mcrossley

  • Forecaster
  • *****
  • Posts: 1062
    • Wilmslow Astro
Re: rainfall offset.
« Reply #12 on: February 27, 2023, 05:36:34 PM »
OK, if it is using the usual OS rain gauge then I believe it is actually 0.04 inches per tip not 1 mm.

So, the multiplier should be 4.0 exactly (as posted above by @Mattk)
« Last Edit: February 27, 2023, 05:50:24 PM by mcrossley »
Mark

Offline CW2274

  • Forecaster
  • *****
  • Posts: 6601
    • Conditions @ CW2274 West Tucson-Painted Hills Ranch
Re: rainfall offset.
« Reply #13 on: February 27, 2023, 05:45:05 PM »
OK, if it is using the usual OS rain gauge then I believe it is actually 0.04 inches per tip not 1 mm.
So, does that mean if you get 0.03" of rain, nothing is displayed, and then rain is displayed in only 0.04" increments after that?  :???:

Offline mcrossley

  • Forecaster
  • *****
  • Posts: 1062
    • Wilmslow Astro
Re: rainfall offset.
« Reply #14 on: February 27, 2023, 05:48:06 PM »
OK, if it is using the usual OS rain gauge then I believe it is actually 0.04 inches per tip not 1 mm.
So, does that mean if you get 0.03" of rain, nothing is displayed, and then rain is displayed in only 0.04" increments after that?  :???:
Yes.
Mark

Offline CW2274

  • Forecaster
  • *****
  • Posts: 6601
    • Conditions @ CW2274 West Tucson-Painted Hills Ranch
Re: rainfall offset.
« Reply #15 on: February 27, 2023, 05:49:41 PM »
Wow. Never knew that. No bueno IMO. Thank you.

Offline SnowHiker

  • Forecaster
  • *****
  • Posts: 352
Re: rainfall offset.
« Reply #16 on: February 27, 2023, 05:58:14 PM »
OK, if it is using the usual OS rain gauge then I believe it is actually 0.04 inches per tip not 1 mm.

So, the multiplier should be 4.0 exactly.

Even the Davis rain gauge is nowhere that accurate.  I believe stations like OS are made to switch between metric and English units with no change in the rain gauge.  As mentioned the difference between 1 mm and .04" is most likely well within specs and the inherent accuracy of the gauge.

So yes, a multiplier of four, or 3.937 really isn't going to make a significant difference.  I would go with the higher, because even assuming it's accurate, it's going to be reporting up to .04" low on any storm to begin with.
« Last Edit: February 27, 2023, 05:59:57 PM by SnowHiker »