Author Topic: Davis VP2 vs Kestrel D3  (Read 3152 times)

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Offline jgentry

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Davis VP2 vs Kestrel D3
« on: January 17, 2019, 06:57:44 PM »
So I got a Kestrel D3 meter two days ago and the humidity sensor is out performing the Sensirion SHT 75 on the high end. The SHT-31 is performing basically the same as the 75. Why can’t Davis use a good humidity sensor like Kestrel does? The Kestrel unit has an accuracy of +/- 2% I think Davis should abandon the Sensirion sensors. What do y’all think?
« Last Edit: January 17, 2019, 06:59:27 PM by jgentry »
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Offline Mattk

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Re: Davis VP2 vs Kestrel D3
« Reply #1 on: January 17, 2019, 09:35:39 PM »
So is this one of those comparison things when you are not really having a comparison as the comparison is based on sensors separated by distance? 

Offline openvista

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Re: Davis VP2 vs Kestrel D3
« Reply #2 on: January 18, 2019, 12:17:49 PM »
[The following is addressed to whomever is reading this thread, not specifically the OP]:

If the SHT31 read 99% or 100% recently then, perhaps, the 96% reading is valid. But if you notice, as I and many others have, that the ceiling for the sensor goes from, let's say, 98% upon installation but over time drops to 96%, then you can assume that the sensor isn't going to read properly during fog. I've got three 31s. The humidity maxes are: 97% (newest), 96% (2nd oldest), 95% (oldest).

Kestrel produces their own in-house sensor. It's hard to imagine why Davis would pay an engineering team to do the same. If Davis were selling these instruments primarily to people who knew better and it were a matter of life and death or they were in a higher market tier, then we might see a different response. Kestrel, on the other hand, sells its equipment to the military, firefighters, sports teams (heat stress on the field), storm chasers and other critical industries.

Based on my own tests involving visits to local airports and other professional weather stations, I can attest to their accuracy. I know another forum member, Ken, who has a masters in met, who has tinkered with them extensively and will attest to their accuracy.  They are good, reliable devices when used properly.
« Last Edit: January 18, 2019, 12:38:18 PM by openvista »
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Offline Ken7

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Re: Davis VP2 vs Kestrel D3
« Reply #3 on: January 18, 2019, 01:05:31 PM »
Openvista is correct. The Kestrel sensors are indeed more accurate. I've had several instances of widespread fog and my Davis went no higher than 95% while my Kestrel reported 100%. I've since cheated, in terms of reporting to WU, by performing the good ol' 'humidity stretch', but even there I still only get to 99%. Of course doing the humidity stretch will create errors in the lower humidity regions, but it is what it is.

Offline CW2274

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Re: Davis VP2 vs Kestrel D3
« Reply #4 on: January 18, 2019, 02:49:56 PM »
If the SHT31 read 99% or 100% recently then, perhaps, the 96% reading is valid. But if you notice, as I and many others have, that the ceiling for the sensor goes from, let's say, 98% upon installation but over time drops to 96%, then you can assume that the sensor isn't going to read properly during fog. I've got three 31s. The humidity maxes are: 97% (newest), 96% (2nd oldest), 95% (oldest).
The 31 I'm using now has been in service ~2.5 years and hit 100% three times in the last two weeks. Granted, if you blinked you missed it, but happened none the less. When it wasn't at 100, 98% was the norm. Once again, looks like drier climates are the 31's friend, and frankly, I think having a stronger fan helps return it to normalcy (drying it out more efficiently) more so that not having a fan. Just to add, whether it matters or not, I also use the SF2 filter cap.

Offline Ken7

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Re: Davis VP2 vs Kestrel D3
« Reply #5 on: January 18, 2019, 06:23:10 PM »
But the problem is when it dries out it then often reads too dry.

Offline CW2274

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Re: Davis VP2 vs Kestrel D3
« Reply #6 on: January 18, 2019, 06:54:50 PM »
But the problem is when it dries out it then often reads too dry.
I don't have this problem. As stated above, I think climate has much to do the sensor's overall performance.

Offline Ken7

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Re: Davis VP2 vs Kestrel D3
« Reply #7 on: January 18, 2019, 07:08:16 PM »
But the problem is when it dries out it then often reads too dry.
I don't have this problem. As stated above, I think climate has much to do the sensor's overall performance.

The bottom line is that if a sensor can only perform well in 'some locales', then there is a problem with the sensor.

Offline CW2274

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Re: Davis VP2 vs Kestrel D3
« Reply #8 on: January 18, 2019, 07:09:55 PM »
Of course. Never said it was right, just better.

Offline jgentry

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Re: Davis VP2 vs Kestrel D3
« Reply #9 on: January 18, 2019, 09:01:25 PM »
As jerryg has pointed out in another thread, the Sensirion sensors are designed for indoor applications and not outdoor ones.
Davis Vantage Pro2 & WeatherFlow Tempest. WU: KXALJEMI2, KALJEMIS7, KFLPANAM363 & KALTHORS2. CWOP/APRS: C6353 & E6358

Offline jgentry

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Re: Davis VP2 vs Kestrel D3
« Reply #10 on: January 18, 2019, 09:01:53 PM »
So is this one of those comparison things when you are not really having a comparison as the comparison is based on sensors separated by distance?

The units are nearby.
Davis Vantage Pro2 & WeatherFlow Tempest. WU: KXALJEMI2, KALJEMIS7, KFLPANAM363 & KALTHORS2. CWOP/APRS: C6353 & E6358

Offline jgentry

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Re: Davis VP2 vs Kestrel D3
« Reply #11 on: January 18, 2019, 09:29:47 PM »
[The following is addressed to whomever is reading this thread, not specifically the OP]:

If the SHT31 read 99% or 100% recently then, perhaps, the 96% reading is valid. But if you notice, as I and many others have, that the ceiling for the sensor goes from, let's say, 98% upon installation but over time drops to 96%, then you can assume that the sensor isn't going to read properly during fog. I've got three 31s. The humidity maxes are: 97% (newest), 96% (2nd oldest), 95% (oldest).

Kestrel produces their own in-house sensor. It's hard to imagine why Davis would pay an engineering team to do the same. If Davis were selling these instruments primarily to people who knew better and it were a matter of life and death or they were in a higher market tier, then we might see a different response. Kestrel, on the other hand, sells its equipment to the military, firefighters, sports teams (heat stress on the field), storm chasers and other critical industries.

Based on my own tests involving visits to local airports and other professional weather stations, I can attest to their accuracy. I know another forum member, Ken, who has a masters in met, who has tinkered with them extensively and will attest to their accuracy.  They are good, reliable devices when used properly.

What’s interesting is that RainWise uses the Sensirion sensor also. If Davis would fix this problem with the humidity sensor, along with their rain gauge, they would have a heck of a station.
Davis Vantage Pro2 & WeatherFlow Tempest. WU: KXALJEMI2, KALJEMIS7, KFLPANAM363 & KALTHORS2. CWOP/APRS: C6353 & E6358

Offline jgentry

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Re: Davis VP2 vs Kestrel D3
« Reply #12 on: January 18, 2019, 09:52:08 PM »
Will also note that I’m using the Sensirion SHT-75 and it typically tops off at 98-99%. I’ve heard that when the sensor is reporting 99% it’s basically saying that the air is fully saturated.
Davis Vantage Pro2 & WeatherFlow Tempest. WU: KXALJEMI2, KALJEMIS7, KFLPANAM363 & KALTHORS2. CWOP/APRS: C6353 & E6358

Offline openvista

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Re: Davis VP2 vs Kestrel D3
« Reply #13 on: January 19, 2019, 09:29:12 AM »
What’s interesting is that RainWise uses the Sensirion sensor also. If Davis would fix this problem with the humidity sensor, along with their rain gauge, they would have a heck of a station.

Yes, but does the RainWise sensor (which is a Sensirion SHT15) reach 99/100% after being the field for a year? What is the usual max for those stations in fog over time? I'm talking overall, not one-off examples.

I've yet to see any consumer segment weather station that consistently hits 99/100% in fog. Normally I see 96% to 98% regardless of brand. That's almost always within or very close to specs (+/- 3/4/5%), so I don't think the manufacturers see that as an issue.

Let's put it this way. Davis has been aware (at least since last Spring) that their sensors can be well outside specs in mid range humidities. Do they seem concerned to you? Why then should they care about a problem that lies mostly within specs?
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Offline jgentry

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Re: Davis VP2 vs Kestrel D3
« Reply #14 on: January 19, 2019, 10:52:17 AM »
What’s interesting is that RainWise uses the Sensirion sensor also. If Davis would fix this problem with the humidity sensor, along with their rain gauge, they would have a heck of a station.

Yes, but does the RainWise sensor (which is a Sensirion SHT15) reach 99/100% after being the field for a year? What is the usual max for those stations in fog over time? I'm talking overall, not one-off examples.

I've yet to see any consumer segment weather station that consistently hits 99/100% in fog. Normally I see 96% to 98% regardless of brand. That's almost always within or very close to specs (+/- 3/4/5%), so I don't think the manufacturers see that as an issue.

Let's put it this way. Davis has been aware (at least since last Spring) that their sensors can be well outside specs in mid range humidities. Do they seem concerned to you? Why then should they care about a problem that lies mostly within specs?

They should care considering that professionals are using their stations.
Davis Vantage Pro2 & WeatherFlow Tempest. WU: KXALJEMI2, KALJEMIS7, KFLPANAM363 & KALTHORS2. CWOP/APRS: C6353 & E6358

Offline jgentry

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Re: Davis VP2 vs Kestrel D3
« Reply #15 on: January 19, 2019, 11:01:04 AM »
What’s interesting is that RainWise uses the Sensirion sensor also. If Davis would fix this problem with the humidity sensor, along with their rain gauge, they would have a heck of a station.

Yes, but does the RainWise sensor (which is a Sensirion SHT15) reach 99/100% after being the field for a year? What is the usual max for those stations in fog over time? I'm talking overall, not one-off examples.

I've yet to see any consumer segment weather station that consistently hits 99/100% in fog. Normally I see 96% to 98% regardless of brand. That's almost always within or very close to specs (+/- 3/4/5%), so I don't think the manufacturers see that as an issue.

Let's put it this way. Davis has been aware (at least since last Spring) that their sensors can be well outside specs in mid range humidities. Do they seem concerned to you? Why then should they care about a problem that lies mostly within specs?

But I don’t know about the RainWise stations.
Davis Vantage Pro2 & WeatherFlow Tempest. WU: KXALJEMI2, KALJEMIS7, KFLPANAM363 & KALTHORS2. CWOP/APRS: C6353 & E6358

Offline Ken7

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Re: Davis VP2 vs Kestrel D3
« Reply #16 on: January 19, 2019, 11:04:42 AM »
I have one Rainwise station in fairly close proximity to me. When I first started looking at it, it seemed to be quite close in terms of RH/DP at most moisture levels. Now it has one of the biggest deviations at high & low moisture levels, from not only nearby PWS, but also APRSWXNET/CWOP & certainly NWS/FAA locations. So it certainly seems it has drifted quite a bit.
« Last Edit: January 19, 2019, 11:07:08 AM by Ken7 »

Offline jgentry

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Re: Davis VP2 vs Kestrel D3
« Reply #17 on: January 19, 2019, 12:01:34 PM »
I have one Rainwise station in fairly close proximity to me. When I first started looking at it, it seemed to be quite close in terms of RH/DP at most moisture levels. Now it has one of the biggest deviations at high & low moisture levels, from not only nearby PWS, but also APRSWXNET/CWOP & certainly NWS/FAA locations. So it certainly seems it has drifted quite a bit.

Thanks for the input! It’s sad to spend a $1,000 on a station but end up getting a humidity sensor that’s designed for indoor use.
Davis Vantage Pro2 & WeatherFlow Tempest. WU: KXALJEMI2, KALJEMIS7, KFLPANAM363 & KALTHORS2. CWOP/APRS: C6353 & E6358

Offline openvista

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Re: Davis VP2 vs Kestrel D3
« Reply #18 on: January 19, 2019, 12:19:27 PM »
They should care considering that professionals are using their stations.

Davis will care when customers start bolting for other stations, and they can connect that phenomenon to this issue.

I have an SHT15 (same sensor as in the RainWise) and it has measured progressively drier in saturated air over time. I think it's max is 96% at last check -- it's out of service now. It was in the field for a couple years in a 24hr aspirated shield. From what I understand, Davis' mishandling of sensors (which is given as a reason for Davis' bad humidity measurements) is a relatively recent thing. I don't believe it dates back to the 15. So, perhaps, what I'm seeing from an otherwise perfectly functional SHT15 is not that unusual, particularly among aspirated sensors (aspiration being just an accelerated form of aging according to some)?

I'd need to collect some data from other 15s from a variety of settings & labels to draw a firm conclusion. But what I can say is that my 15 isn't very far off in performance from my 31 sensors (at least in terms of humidity - it has a wet bias in the middle and a dry bias at the top). Someone suggested on this forum that the 31 is just a tweaked 15 made on the same die, using the same architecture, bus, etc. That would explain a lot, if true.
« Last Edit: January 19, 2019, 05:10:16 PM by openvista »
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Offline jgentry

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Re: Davis VP2 vs Kestrel D3
« Reply #19 on: January 19, 2019, 05:40:54 PM »
They should care considering that professionals are using their stations.

Davis will care when customers start bolting for other stations, and they can connect that phenomenon to this issue.

I have an SHT15 (same sensor as in the RainWise) and it has measured progressively drier in saturated air over time. I think it's max is 96% at last check -- it's out of service now. It was in the field for a couple years in a 24hr aspirated shield. From what I understand, Davis' mishandling of sensors (which is given as a reason for Davis' bad humidity measurements) is a relatively recent thing. I don't believe it dates back to the 15. So, perhaps, what I'm seeing from an otherwise perfectly functional SHT15 is not that unusual, particularly among aspirated sensors (aspiration being just an accelerated form of aging according to some)?

I'd need to collect some data from other 15s from a variety of settings & labels to draw a firm conclusion. But what I can say is that my 15 isn't very far off in performance from my 31 sensors (at least in terms of humidity - it has a wet bias in the middle and a dry bias at the top). Someone suggested on this forum that the 31 is just a tweaked 15 made on the same die, using the same architecture, bus, etc. That would explain a lot, if true.

Oh wow. But I really wouldn’t know what other stations to bolt too. Lol.

Unless I had $3,000 laying around in which I don’t.
Davis Vantage Pro2 & WeatherFlow Tempest. WU: KXALJEMI2, KALJEMIS7, KFLPANAM363 & KALTHORS2. CWOP/APRS: C6353 & E6358

Offline WiFiLogger

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Re: Davis VP2 vs Kestrel D3
« Reply #20 on: January 19, 2019, 05:49:04 PM »
What do you thing about adapter between ISS and sensor.
Adapter will feed ISS with temp and HUM, but on input adapter will take other sensors than Sensirion
What do you think about adapter?

Offline jgentry

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Re: Davis VP2 vs Kestrel D3
« Reply #21 on: January 19, 2019, 10:25:48 PM »
What do you thing about adapter between ISS and sensor.
Adapter will feed ISS with temp and HUM, but on input adapter will take other sensors than Sensirion
What do you think about adapter?

I personally like the idea! What other sensors are you thinking about using?
Davis Vantage Pro2 & WeatherFlow Tempest. WU: KXALJEMI2, KALJEMIS7, KFLPANAM363 & KALTHORS2. CWOP/APRS: C6353 & E6358

Offline Bashy

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Re: Davis VP2 vs Kestrel D3
« Reply #22 on: January 19, 2019, 11:32:20 PM »
I have never seen my davis go above 97% from day dot and thats in fog, and rare, it normally tops out at 96%
Kind regards
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Offline weather34

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Re: Davis VP2 vs Kestrel D3
« Reply #23 on: January 20, 2019, 02:17:04 AM »
If the SHT31 read 99% or 100% recently then, perhaps, the 96% reading is valid. But if you notice, as I and many others have, that the ceiling for the sensor goes from, let's say, 98% upon installation but over time drops to 96%, then you can assume that the sensor isn't going to read properly during fog. I've got three 31s. The humidity maxes are: 97% (newest), 96% (2nd oldest), 95% (oldest).
The 31 I'm using now has been in service ~2.5 years and hit 100% three times in the last two weeks. Granted, if you blinked you missed it, but happened none the less. When it wasn't at 100, 98% was the norm. Once again, looks like drier climates are the 31's friend, and frankly, I think having a stronger fan helps return it to normalcy (drying it out more efficiently) more so that not having a fan. Just to add, whether it matters or not, I also use the SF2 filter cap.

on the 31 non aspirated your not alone ive almost hit the magic 100 but seen 99 on numerous occasions(dense fog) and i dont live in a drier climate 150 meters from sea front lucky if we see anything below 35% during peak dry summer months but who knows how close it gets as the display on vp2 console doesnt cater for the decimal places i.e 99.4%..

im not convinced on aspirated methods when dealing with humidity measurements.

Offline CW2274

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Re: Davis VP2 vs Kestrel D3
« Reply #24 on: January 20, 2019, 04:23:32 AM »
If the SHT31 read 99% or 100% recently then, perhaps, the 96% reading is valid. But if you notice, as I and many others have, that the ceiling for the sensor goes from, let's say, 98% upon installation but over time drops to 96%, then you can assume that the sensor isn't going to read properly during fog. I've got three 31s. The humidity maxes are: 97% (newest), 96% (2nd oldest), 95% (oldest).
The 31 I'm using now has been in service ~2.5 years and hit 100% three times in the last two weeks. Granted, if you blinked you missed it, but happened none the less. When it wasn't at 100, 98% was the norm. Once again, looks like drier climates are the 31's friend, and frankly, I think having a stronger fan helps return it to normalcy (drying it out more efficiently) more so that not having a fan. Just to add, whether it matters or not, I also use the SF2 filter cap.

vp2 console doesnt cater for the decimal places i.e 99.4%..

im not convinced on aspirated methods when dealing with humidity measurements.
No, but software does.

As far as aspiration, I realize it's not SOP for humidity, but it's damn sure better for me than no fan at all, not even close.