Topic: Does the Davis Vantage Pro 2 24hr FARS performs well?

[ct]

I can only get the i2c version.

This is one of the many reasons why I build my own ISS for the Davis FARS - use any sensors I like.

I'll be getting some of these when the seller returns from vacation
https://www.tindie.com/products/closedcube/sht35-d-digital-humidity-and-temperature-sensor/

[belfryboy]

I could save you the trouble, I have an SHT31-D mounted on one of my "heat Island" boards with Sensirion filtercap, PM me if you're interested, Although that looks pretty good to me, and a bargain at that price.

[ValentineWeather]

Hey guys, so, i bought the DFARS and added a new fan and its connected to a 12v psu for 24hr
From what i have read above, i should have gone 24hr FARS?

With that in mind, what sort of differences am i going to see and is there a thread with any comparison data over the 2 please?

You will be okay with the higher shield mount (12'). Sensor isn't exposed the same as ground level with better air movement all the time but if you do go to ground level the 24 hour shield would work better.
As long as there is a nice breeze both do well but low wind days is where you will see the main difference between Dfars and 24 hr Fars. My test were showing delta Temp 1-2 F on low breeze days which is rare here but most days 0F to .5 F.

[Bashy]

Cheers Randy, hate the idea of buying the wrong thing, full setup cost me around the £1900 mark

[jgentry]

But I would love to see the performance of a Belfry Boy SHT 31 in a 24hr FARS. My thinking that the response time would be better than the Davis version of the SHT 31.

I've screwed up here already, but the SHT31 is made by Sensirion, not Davis or Belfry Boy. How could they be different?

Chip is made by Sensirion but the the design of the sensor module is different. Belfry Boy version uses the Sensirion filter cap and he places the sensor chip in a "heat island" which helps with response time. You can see his design here: http://belfryboyweatherbits.blogspot.com/p/sht15-humdity-sens.html?m=1

If I could get my hands on an SHT31 with the legacy communications protocol then I'd love to give it ago. but in the quauntities that I build Sinsirion won't give me the time of day. I can only get the i2c version.

😞  I just don't understand why Sensirion does this. If they ever do decide to sell you the right pieces, please let us know. I personally would love to have the SHT 35 sensor if it would be available in the legacy protocol version.

[jgentry]

Another question: Would a 24hr FARS along with the temp/hum sensor be damaged if it's out in the open farm with different sprays (pesticides and other types of sprays) hitting the station (even if it's a light sprinkling of the spray)?

[ValentineWeather]

Most likely anything other than H20 mist could cause harm. I would check with Sensirion and see if they have tested for chemicals.

[CW2274]

Another question: Would a 24hr FARS along with the temp/hum sensor be damaged if it's out in the open farm with different sprays (pesticides and other types of sprays) hitting the station (even if it's a light sprinkling of the spray)?

Wouldn't be my first option. Certainly one way to find out...

[ValentineWeather]

Here is what I found.

Quote: Due to minimal package volume and the membrane’s high water vapor permeability, the response time of the relative humidity and temperature signal is identical to the value achieved by the uncovered sensor. Although the membrane option provides perfect protection against water and dust ingress according to IP67, it does not in general prevent contamination from volatile chemicals. More details on contamination can be found in the document "Handling Instructions for Humidity Sensors". All SHT3x sensors can be ordered in tape and reel packaging; the reels are delivered in sealed antistatic ESD bags. Please find more details in the relevant datasheet.

Link to handling PDF: https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/2_Humidity_Sensors/Sensirion_Humidity_Sensors_Handling_Instructions_V4.pdf

[jgentry]

Thanks! I have a VP2 station & a temp/hum station out in the field. I was concerned with chemicals getting into the sensor with the FARS so I've decided for those two stations is to stick with a passive shield.

[CW2274]

Thanks! I have a VP2 station & a temp/hum station out in the field. I was concerned with chemicals getting into the sensor with the FARS so I've decided for those two stations is to stick with a passive shield.

Certainly better than a fan sucking "stuff" in. I'd still do what I could to avoid spray on the ISS, could harm the plastics in the long term.

[ValentineWeather]

What you could do while spraying is wrap shield in garbage bag. I've do it while I sprayed my yard and even mowed before. I just unplug the Temp/hum sensor prior.

[jgentry]

This station is over at a friend of mine's farm. They typically try to spray away from the stations as much as possible.

[CW2274]

I just unplug the Temp/hum sensor prior.

Nah, just leave it and call it "Netatmo" mode.

[jgentry]

I just ordered a 24hr FARS temp/hum station from Ryan at Scaled Instruments. Can't wait to get my hands on it! Also got a RainWise RainNew 111 8" gauge coming also (whenever Rainman Weather has it back in stock).

[ValentineWeather]

Nice Rainwise sells directly fast shipping also.

[CW2274]

I just ordered a 24hr FARS temp/hum station from Ryan at Scaled Instruments. Can't wait to get my hands on it! Also got a RainWise RainNew 111 8" gauge coming also (whenever Rainman Weather has it back in stock).

Good deal. There's a few of us happily with this setup. Are you planning to hard wire the RW to the ISS?

[jgentry]

I just ordered a 24hr FARS temp/hum station from Ryan at Scaled Instruments. Can't wait to get my hands on it! Also got a RainWise RainNew 111 8" gauge coming also (whenever Rainman Weather has it back in stock).

Good deal. There's a few of us happily with this setup. Are you planning to hard wire the RW to the ISS?

Yes sir!

[CW2274]

I just ordered a 24hr FARS temp/hum station from Ryan at Scaled Instruments. Can't wait to get my hands on it! Also got a RainWise RainNew 111 8" gauge coming also (whenever Rainman Weather has it back in stock).

Good deal. There's a few of us happily with this setup. Are you planning to hard wire the RW to the ISS?

Yes sir!

Sweet. Works just like stock and super easy to do.

[jgentry]

So I just converted a passive shield VP2 station to a 24hr FARS over at a friend's business and I can already see the difference with the FARS. He has a passive temp/hum station with the SHT-31 down the hill (but still fairly open) and the comparisons were quite interesting when the storms began to come through the area.

[jgentry]

But I'm definitely curious to know if the Belfry Boy version of the SHT 31 or 35 would had a faster response time in the FARS compared to the Davis version of the SHT-31 in the FARS.

[ValentineWeather]

But I'm definitely curious to know if the Belfry Boy version of the SHT 31 or 35 would had a faster response time in the FARS compared to the Davis version of the SHT-31 in the FARS.

Humm.. I've heard others same the same but I really don't see anything wrong with the current filter, air flow seems sufficient considering console update is 10-12 seconds according to spec sheet on temperature. Fars will increase changes faster sampling air much faster over passive shield but updates will always be the same 10-12 seconds.

In comparison the Thomas traceable high accuracy thermometer I started a thread on has a 1 second response time.

[jgentry]

But I'm definitely curious to know if the Belfry Boy version of the SHT 31 or 35 would had a faster response time in the FARS compared to the Davis version of the SHT-31 in the FARS.

Humm.. I've heard others same the same but I really don't see anything wrong with the current filter, air flow seems sufficient considering console update is 10-12 seconds according to spec sheet on temperature. Fars will increase changes faster sampling air much faster over passive shield but updates will always be the same 10-12 seconds.

In comparison the Thomas traceable high accuracy thermometer I started a thread on has a 1 second response time.

Wow! Can't find that thread that you started. Can you shoot me a link?

[ValentineWeather]

http://www.wxforum.net/index.php?topic=32605.msg329395#msg329395

[dendrite]

The best response time I've gotten from any Sensirion sensor is with the SHT75. Of course that sensor module has the least thermal mass of any of them so it's response shouldn't be much of a surprise. I dealt with frequent RH issues with them after a few weeks of use so I gave up on them. I swear I was getting faster than 12s updates, but don't hold that to me. I'd assume the update interval is handled by the ISS board and not the temp/hum module board, correct? That's the only sensor I used that had a non-Davis PCB.

I'd love to see a similar sensor for the SHT31/35 as the SHT75 was for the SHT15. Of course you have the different sensor versions (Davis uses the legacy IIRC) so maybe it wouldn't be plug-n-play like the 75 is.