Author Topic: Davis VP2 - internal temperature problems  (Read 22223 times)

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Offline kcidwx

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Re: Davis VP2 - internal temperature problems
« Reply #50 on: February 26, 2014, 10:13:09 PM »
They should just give you the sensor with ten feet of cable for the indoor temperature/humidity. Heck, every single Heathkit weather station had one for indoor temperature and a separate one for indoor humidity. Or at least make it an optional accessory for the VP2. Just something that plugs into the console if you want to buy it.

I would make use of it because I use a humidifier or dehumidifier depending on the season and it's nice to monitor it accurately. Plus we all know thermostats aren't very accurate and the sensors on humidifier/dehumidifiers are not accurate either.
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Offline piconut

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Re: Davis VP2 - internal temperature problems
« Reply #51 on: February 26, 2014, 11:20:21 PM »
... Plus we all know thermostats aren't very accurate and the sensors on humidifier/dehumidifiers are not accurate either.


Actually, the sensor on my Nest thermostat is as accurate as the sensor on my Vantage Pro console as the Nest employs a Sensirion SHT20 and the VPro console uses as SHT11.  Both sensors have almost the same temperature accuracy profile and are rated at +/- 0.4°C at 25°C. 
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Offline Joe A

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Re: Davis VP2 - internal temperature problems
« Reply #52 on: March 13, 2014, 02:58:47 PM »
My anecdotal observation after living with the VP2 for 10 years is that -5°F/-3°C is the correct indoor temp calibration adjustment with the back light always on. I have found this to be acceptable for the 60°-80° range, which is a broad enough range for my office and home. If, however, you live in Phoenix AZ, for example, and you have no A/C, I have never tested a range of 65°-120°... and I'm not planning on doing that anytime in the future!!!

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Offline gotty1

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Re: Davis VP2 - internal temperature problems
« Reply #53 on: May 03, 2014, 06:01:33 PM »
It has been some time since I raised the question of the internal temperature problem with the backlight on permanently.

Despite comments that the offset should be linear, this is definitely not the case. I decided to do some careful experimentation and observation and found that the offset at true ambient temperature of 10C the console was reading 14.3C (so required an offset of -4.3C), but at a true ambient temperature of 25C, an offset of only -0.2C was needed. But even the delta-T wasn't linear.

Careful examination (including IR imaging) showed, a bit to my surprise, that the problem was
mainly radiated heat from the adjacent backlight components, rather than conduction or convection.

So the solution was obvious, and after a zero-cost mod I now have (with no offset) 10C reading 10.5C and at 25C it is reading 25.2C. And this has been pretty much fixed using an offset of -0.3C

The poor air circulation still results in a significant delay in registering the room temperature (possibly resolvable with better air circulation), but it is at least now accurate enough to monitor and analyse the room temperature.

Offline graham999au

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Re: Davis VP2 - internal temperature problems
« Reply #54 on: May 22, 2014, 03:29:19 AM »
I made a ribbon cable to separate my WeatherlinkIP connection from the console and also left the battery cover off. I can report the internal temp is more accurate, certainly better than the 4 degrees CELCIUS offset I had before this modification. Bring on the new VP console!!

Offline ShastaSnoDog

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Re: Davis VP2 - internal temperature problems
« Reply #55 on: August 10, 2014, 08:15:10 PM »
It has been some time since I raised the question of the internal temperature problem with the backlight on permanently.

Despite comments that the offset should be linear, this is definitely not the case. I decided to do some careful experimentation and observation and found that the offset at true ambient temperature of 10C the console was reading 14.3C (so required an offset of -4.3C), but at a true ambient temperature of 25C, an offset of only -0.2C was needed. But even the delta-T wasn't linear.

Careful examination (including IR imaging) showed, a bit to my surprise, that the problem was
mainly radiated heat from the adjacent backlight components, rather than conduction or convection.

So the solution was obvious, and after a zero-cost mod I now have (with no offset) 10C reading 10.5C and at 25C it is reading 25.2C. And this has been pretty much fixed using an offset of -0.3C

The poor air circulation still results in a significant delay in registering the room temperature (possibly resolvable with better air circulation), but it is at least now accurate enough to monitor and analyse the room temperature.
Gotty1, - My new VP2 Pro reads inside temperature 4 to 5 degrees F high with the light OFF.  This is the second console with the same error.

Would you please share your zero-cost modification?  I have read through this entire thread, because like you, I purchased Davis based on the advertised specs.  I have spoken with Davis Tech Support Management, and was told that the WeatherLinkIP logger itself produces enough heat that Davis has included a 4-degree F offset when that unit is identified as connected.  I cannot understand how the VP2 can sense which logger is attached.

graham999au, - Thanks for your posting.  Your posting and the Tech Support Manager’s statement confirm that the sensor is probably accurate, although the system’s console display is does not represent ambient air temperature, and is therefore inaccurate.  IMO, it is silly to quote an NIST accuracy of 1-degree F with no means for the user to know what the sensed temperature is.

Has anyone determined if it is possible to purchase an external indoor sensor that will attach to the VP2 Pro console without voiding warranty?

Offline ValentineWeather

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Re: Davis VP2 - internal temperature problems
« Reply #56 on: August 11, 2014, 12:40:51 AM »

Gotty1, - My new VP2 Pro reads inside temperature 4 to 5 degrees F high with the light OFF.  This is the second console with the same error.


[/quote]

Compared to what? I call BS because with scientific calibrated thermometer I've never seen over a couple degrees. Thats with no air flow with air flow .4 tenths is the max off set.
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Offline pfletch101

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Re: Davis VP2 - internal temperature problems
« Reply #57 on: August 11, 2014, 09:32:00 AM »
Gotty1, - My new VP2 Pro reads inside temperature 4 to 5 degrees F high with the light OFF.  This is the second console with the same error.

Out of interest, are you using a USB Weatherlink?
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Offline ShastaSnoDog

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Re: Davis VP2 - internal temperature problems
« Reply #58 on: August 11, 2014, 11:33:24 AM »

Gotty1, - My new VP2 Pro reads inside temperature 4 to 5 degrees F high with the light OFF.  This is the second console with the same error.



Compared to what? I call BS because with scientific calibrated thermometer I've never seen over a couple degrees. Thats with no air flow with air flow .4 tenths is the max off set.
[/quote]
Thanks ValentineWeather,

Brett, Technical Support Manager at Davis in Hayward, told me that the IP data logger produces so much heat that the VP2 console is programmed to sense that logger is connected and offset the displayed temperature three degrees lower than sensed.  I suppose he could be wrong.

Brett noted that air motion (ceiling fan off or on) would influence how much of the data logger's heat reached the sensor, and that the offset was not an elegant solution.

Because I lack an NIST-traceable reference, I used several other temperature measuring devices, including two Oregon Scientific Model EMR812s, a Fluke thermocouple, a LaCross WS-9611U, aThermoWorks Thermapen 5, a AllTrade 480742 infrared thermometer, and the Davis WeatherMonitor II that is being replaced.  I realize that none of those may be correct, yet they all indicate within a degree of each other and substantially lower than either the original VP2 or its replacement.  It could be that the VP2 Pro is correct and the others are all offset the same, but those odds seem long.

Also, when the VP2 is first turned on, after being off for a few hours, it indicates what those other instruments display and then creeps up to much higher.

What instrument do you use to be certain that your VP2 has a maximum of 0.04-degree Fahrenheit offset from true ambient temperature? If you don't mind, where did you get your reference instrument, and what did it cost?

I am willing to pay something extra to have the VP2 console display the inside ambient temperature within a degree of actual, but I have not found a method to do that yet.  I am looking for advice.

Offline ShastaSnoDog

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Re: Davis VP2 - internal temperature problems
« Reply #59 on: August 11, 2014, 11:38:31 AM »
Gotty1, - My new VP2 Pro reads inside temperature 4 to 5 degrees F high with the light OFF.  This is the second console with the same error.

Out of interest, are you using a USB Weatherlink?
pfletch101,

No, I have the WeatherLinkIP logger attached.  Per Davis Technical Support, that is a big part of the display inaccuracy.  They say the IP logger puts out lots of heat and causes the sensor to respond to ambient temperature, influenced by that added heat.

Offline Joe A

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Re: Davis VP2 - internal temperature problems
« Reply #60 on: August 11, 2014, 12:38:56 PM »
The cheapest and easiest method of removing the data logger heat source is to use a 6316 wireless PC receiver (http://www.weatherbuffs.com/Davis_Wireless_Weather_Envoy_Part_6316_p/d-6316.htm). You'll plug your datalogger into the 6316 instead of your console and connect the 6316 to your computer. Now you can move your 6312 console anywhere within its 1000ft range and actually end up having two "consoles" in range; one on your computer screen and, of course, your newly freed console. While this will resolve the datalogger heat issue, it will NOT resolve the backlight heat issue, which as previously noted is anecdotally observed at causing an increase in indoor temperature of +5°. When we have the backlight on, we simply subtract 5° from what we see.

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Offline ShastaSnoDog

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Re: Davis VP2 - internal temperature problems
« Reply #61 on: August 11, 2014, 01:29:50 PM »
The cheapest and easiest method of removing the data logger heat source is to use a 6316 wireless PC receiver (http://www.weatherbuffs.com/Davis_Wireless_Weather_Envoy_Part_6316_p/d-6316.htm). You'll plug your datalogger into the 6316 instead of your console and connect the 6316 to your computer. Now you can move your 6312 console anywhere within its 1000ft range and actually end up having two "consoles" in range; one on your computer screen and, of course, your newly freed console. While this will resolve the datalogger heat issue, it will NOT resolve the backlight heat issue, which as previously noted is anecdotally observed at causing an increase in indoor temperature of +5°. When we have the backlight on, we simply subtract 5° from what we see.

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Thank you for the idea Joe,

Somewhere here, a member posted that he had made up a cable from the VP2 to the WeatherLinkIP data logger so that the logger's heat source did not influence the displayed inside temperature.  I could not tell if that was from the multi-pin header or between the logger part and the Cat 5 part.  That cable seems lots cheaper than the remote sensor.

Secondly, the OP wrote that he had found a way to mitigate the heating of the light, which I would also like to be able to leave on sometimes.  I could not find what that mitigation was.  Does anyone know?

It seems that with these two solutions applied, and a minor calibration offset, the VP2 could meet its advertised specification with any type of logger and with the light on or off.  I would like that result.  I suspect others would as well.

Offline pfletch101

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Re: Davis VP2 - internal temperature problems
« Reply #62 on: August 11, 2014, 01:44:13 PM »
Gotty1, - My new VP2 Pro reads inside temperature 4 to 5 degrees F high with the light OFF.  This is the second console with the same error.

Out of interest, are you using a USB Weatherlink?
pfletch101,

No, I have the WeatherLinkIP logger attached.  Per Davis Technical Support, that is a big part of the display inaccuracy.  They say the IP logger puts out lots of heat and causes the sensor to respond to ambient temperature, influenced by that added heat.

The USB Weatherlink has similar (though slightly less severe) problems, but Davis has repeatedly claimed that it doesn't - I am fascinated that they now apparently admit them for the IP version.
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Offline Joe A

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Re: Davis VP2 - internal temperature problems
« Reply #63 on: August 11, 2014, 01:59:06 PM »
There are some very creative folks that can conjure some interesting solutions. I was under the impression that the pinning was proprietary. But I would also figure that someone, given the right amount of time, could decipher the pinning and come up with work-arounds. Of what I read, many folks were considering expensive calibration devices. And for most common folks, freeing up the console is desirable anyhow. Having two weather stations right next to each other is a bit of a waste or at least not optimizing the system. For me, freeing up the console and having virtually two weather consoles in separate places solved two issues at once and was well worth the upgrade.

And while subtracting 5° in your head when the back light is on wouldn't be acceptable for many folks, especially those who are charting, graphing, storing and reviewing data en masse, for most non-mission critical applications like observing weather at our ranch, -5° is a simple and accurate enough, proximate result for us. That said, Davis should have certainly found corrections to these issues by now like measuring the precise temperature of the back light and its effect on its closed environment and automatically making compensatory adjustments as the unit heats and settles at its max point. And maybe there's a technical reason, but why not have a plug in the back of the console only and moving the data logger a couple of feet away from the console in-line. As far as I can tell, a plug generates no heat. It's the datalogger that's working and generating heat. Or am I wrong about this?

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Offline pfletch101

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Re: Davis VP2 - internal temperature problems
« Reply #64 on: August 11, 2014, 02:38:41 PM »
My preferred solution, which I would have thought would have been even easier for Davis to implement, would have been to supply, as an option, a plug-in auxiliary internal temperature/humidity sensor. This could come in a small, well-ventilated enclosure either on a short cable or configured with a rigid standoff containing a certain amount of thermal insulation to allow it to plug directly in to a dedicated socket on the side or bottom edge of the console. Since the options for those who care about accurate indoor temperature measurements (and I know that not everyone does) are otherwise limited, I would not have objected to a reasonable (~ $50.00) price for this as an accessory.
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Offline ShastaSnoDog

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Re: Davis VP2 - internal temperature problems
« Reply #65 on: August 11, 2014, 03:41:17 PM »
My preferred solution, which I would have thought would have been even easier for Davis to implement, would have been to supply, as an option, a plug-in auxiliary internal temperature/humidity sensor. This could come in a small, well-ventilated enclosure either on a short cable or configured with a rigid standoff containing a certain amount of thermal insulation to allow it to plug directly in to a dedicated socket on the side or bottom edge of the console. Since the options for those who care about accurate indoor temperature measurements (and I know that not everyone does) are otherwise limited, I would not have objected to a reasonable (~ $50.00) price for this as an accessory.

I agree.  I think that an an auxiliary inside temperature/humidity sensor should be an option.  Maybe it will become available, as Brett, the Davis Technical Support Manager, asked me if such a solution would be acceptable.  No price was mentioned. 

I told Brett that it would be perfectly satisfying.

Offline ShastaSnoDog

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Re: Davis VP2 - internal temperature problems
« Reply #66 on: August 15, 2014, 04:51:22 PM »
Status. 
Davis Instruments followed-up on this systematic error.

Davis now states that there was NO promise of even an error-fix proposal, let alone a fix.  Additionally, Davis believes that there will be no solution in the short term.

I suppose when the Davis Manager previously asked me if an auxiliary inside temperature/humidity sensor would be acceptable, that question was rhetorical and only intended to give hope to Davis customers.  It is unsatisfying to learn that it was only a question, not a proposal.

Above, pfletch101 reports that Davis has repeatedly claimed that the USB data logger does not cause errors.  Because other Davis customers have reported these errors for a long time, and because Davis did not even acknowledge those reports, it appears that Davis will offer NO LONG TERM SOLUTION either.

IMO, advertising 1-degree NIST accuracy is a fraud when attaching a Davis accessory (data logger) or using the included and needed backlight destroys that accuracy.

I am therefore hoping that folks that came up with home brew methods to allow the VP2 to accurately display inside temperature (within advertised accuracy) when a data logger is connected and with the backlight either off or on.

The data logger induced temperature offset seems especially easy to resolve.  An extension cable to remote the data logger from the VP2 console would fix that issue.

Gotty1 found that the backlight induced temperature offset is not linear and therefore could not be properly addressed with the available fixed offset.  He came up with a zero-cost, and undocumented as far as I can find, means to bring the VP2 within advertised accuracy.

Davis has time to create and sell new products and not enough time to correct design failures. 
- Sell new products = profit. 
- Correct design errors = cost. 
- Davis Instruments did the math.

Offline SpartanWX

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Re: Davis VP2 - internal temperature problems
« Reply #67 on: August 23, 2014, 12:56:55 PM »
It has been some time since I raised the question of the internal temperature problem with the backlight on permanently.

Despite comments that the offset should be linear, this is definitely not the case. I decided to do some careful experimentation and observation and found that the offset at true ambient temperature of 10C the console was reading 14.3C (so required an offset of -4.3C), but at a true ambient temperature of 25C, an offset of only -0.2C was needed. But even the delta-T wasn't linear.

Careful examination (including IR imaging) showed, a bit to my surprise, that the problem was
mainly radiated heat from the adjacent backlight components, rather than conduction or convection.

So the solution was obvious, and after a zero-cost mod I now have (with no offset) 10C reading 10.5C and at 25C it is reading 25.2C. And this has been pretty much fixed using an offset of -0.3C

The poor air circulation still results in a significant delay in registering the room temperature (possibly resolvable with better air circulation), but it is at least now accurate enough to monitor and analyse the room temperature.
What was the fix?  If it is radiated heat, not conduction or convection, I assume some sort of foil shield was used.

Please share the solution you came up with!  Inquiring minds want to know =)

Offline ShastaSnoDog

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Re: Davis VP2 - internal temperature problems
« Reply #68 on: August 23, 2014, 01:40:18 PM »
Yes, Gotty1, PLEASE share what you did to fix the error.

Offline piconut

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Re: Davis VP2 - internal temperature problems
« Reply #69 on: August 23, 2014, 02:11:43 PM »
Yes please!  We gotty have it!   #-o
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Offline dalecoy

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Re: Davis VP2 - internal temperature problems
« Reply #70 on: August 23, 2014, 03:56:04 PM »
Note that gotty1 was last active May 23, 2014, 07:27:26 AM

Offline ShastaSnoDog

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Re: Davis VP2 - internal temperature problems
« Reply #71 on: August 23, 2014, 04:51:01 PM »
Does anyone from Davis Instruments Engineering frequent this forum?  If so, Davis may know how to remote the sensor or shield the internal sensor from the internal heat.

Anybody know?

Offline BigOkie

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Re: Davis VP2 - internal temperature problems
« Reply #72 on: August 23, 2014, 10:01:58 PM »
I believe we discussed all this at length and opined that Davis was saving costs by making the sensors internal.  You *could* create (purchase) an external sensor for indoor I would suppose.  But since I bought the station for outdoor conditions, I let my thermostat tell me what the temperature is.  I also have a wall clock that tells me both inside temp and humidity.
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Offline ShastaSnoDog

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Re: Davis VP2 - internal temperature problems
« Reply #73 on: August 24, 2014, 12:49:07 AM »
BigOkie,

I do not believe that you and I have discussed this failure at length.

It is good to know that you are satisfied with purchasing a recording instrument with the ability to report inside temperatures that is unable to do this within the the advertised accuracy. 

I have spent over a thousand dollars on this system based on Davis Instrument advertisements.

I am interested in knowing how to make my recording device, with the advertised ability to report inside temperatures, and that IS able to report within the its advertised accuracy.  I am willing to do the work.  I am unwilling to spend an additional several hundred dollars to get what I already paid for.  I get that you are unable to understand this.

Thanks for your interest in Davis Instruments.

Go in peace.

Offline BigOkie

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Re: Davis VP2 - internal temperature problems
« Reply #74 on: August 24, 2014, 01:38:33 AM »
BigOkie,

I do not believe that you and I have discussed this failure at length.

It is good to know that you are satisfied with purchasing a recording instrument with the ability to report inside temperatures that is unable to do this within the the advertised accuracy. 

I have spent over a thousand dollars on this system based on Davis Instrument advertisements.

I am interested in knowing how to make my recording device, with the advertised ability to report inside temperatures, and that IS able to report within the its advertised accuracy.  I am willing to do the work.  I am unwilling to spend an additional several hundred dollars to get what I already paid for.  I get that you are unable to understand this.

Thanks for your interest in Davis Instruments.

Go in peace.

OK, then buy something else.  Myself, as I said, I purchased as an OUTDOOR weather station and don't worry about the indoor sensors.

And trust me, I am able to 'understand this'.  No one is twisting your arm to keep the station.  You could always send it back and claim false advertising.  I'm guessing pissing and moaning won't work here.

And 'you and I' haven't discussed the failure at length.  It has been discussed between other posters (me included in that discussion) at extreme length on this very forum on this very post.

Nice attitude there.  Have a pleasant evening.
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