Welcome to the Cumulus Support forum.

Latest Cumulus MX V4 release 4.4.2 (build 4085) - 12 March 2025

Latest Cumulus MX V3 release 3.28.6 (build 3283) - 21 March 2024

Legacy Cumulus 1 release 1.9.4 (build 1099) - 28 November 2014
(a patch is available for 1.9.4 build 1099 that extends the date range of drop-down menus to 2030)

Download the Software (Cumulus MX / Cumulus 1 and other related items) from the Wiki

If you are posting a new Topic about an error or if you need help PLEASE read this first viewtopic.php?p=164080#p164080

VP2 humidity sensor

Discussion specific to Davis weather stations
Post Reply
freddie
Posts: 2870
Joined: Wed 08 Jun 2011 11:19 am
Weather Station: Davis Vantage Pro 2 + Ecowitt
Operating System: GNU/Linux Ubuntu 24.04 LXC
Location: Alcaston, Shropshire, UK
Contact:

VP2 humidity sensor

Post by freddie »

Is it possible to source an alternative humidity sensor for the VP2? I am interested in a more accurate and more responsive replacement.
Freddie
Image
User avatar
steve
Cumulus Author
Posts: 26672
Joined: Mon 02 Jun 2008 6:49 pm
Weather Station: None
Operating System: None
Location: Vienne, France
Contact:

Re: VP2 humidity sensor

Post by steve »

Some people replace the standard SHT11 chip with an SHT15, which gives you more accuracy. I think the response time is the same, though.
Steve
freddie
Posts: 2870
Joined: Wed 08 Jun 2011 11:19 am
Weather Station: Davis Vantage Pro 2 + Ecowitt
Operating System: GNU/Linux Ubuntu 24.04 LXC
Location: Alcaston, Shropshire, UK
Contact:

Re: VP2 humidity sensor

Post by freddie »

steve wrote:Some people replace the standard SHT11 chip with an SHT15, which gives you more accuracy
This is my major concern. I have had two sensors now - both of which under-read when the humidity is high, and over-read when it is low. They don't appear to be capable of recording more than 96% - even in dense fog. I have often thought of asking you if it was possible to provide a (non-linear) calibration setting to overcome this - as well as the over-reading that is notable when the RH falls below about 75-80%.
steve wrote:I think the response time is the same, though.
I can live with that.
Freddie
Image
User avatar
mcrossley
Posts: 14388
Joined: Thu 07 Jan 2010 9:44 pm
Weather Station: Davis VP2/WLL
Operating System: Bullseye Lite rPi
Location: Wilmslow, Cheshire, UK
Contact:

Re: VP2 humidity sensor

Post by mcrossley »

If you are prepared to ditch the VP2 TH board, then the SHT75 will also improve the response time as the chip is effectively on its own heat island. The SHT75 can be just soldered directly onto the end of the Davis TH cable.
freddie
Posts: 2870
Joined: Wed 08 Jun 2011 11:19 am
Weather Station: Davis Vantage Pro 2 + Ecowitt
Operating System: GNU/Linux Ubuntu 24.04 LXC
Location: Alcaston, Shropshire, UK
Contact:

Re: VP2 humidity sensor

Post by freddie »

mcrossley wrote:If you are prepared to ditch the VP2 TH board
Indeed I am! Who supplies the SHT75?
Freddie
Image
User avatar
mcrossley
Posts: 14388
Joined: Thu 07 Jan 2010 9:44 pm
Weather Station: Davis VP2/WLL
Operating System: Bullseye Lite rPi
Location: Wilmslow, Cheshire, UK
Contact:

Re: VP2 humidity sensor

Post by mcrossley »

freddie wrote:Indeed I am! Who supplies the SHT75?
The usual suspects in the UK, Farnell, RS Components, you may be able to find them
elsewhere.
freddie
Posts: 2870
Joined: Wed 08 Jun 2011 11:19 am
Weather Station: Davis Vantage Pro 2 + Ecowitt
Operating System: GNU/Linux Ubuntu 24.04 LXC
Location: Alcaston, Shropshire, UK
Contact:

Re: VP2 humidity sensor

Post by freddie »

Thanks Mark. I'll get ordering!
Freddie
Image
Post Reply