Author Topic: WeatherLink Distorting Indoor Temperature?  (Read 15565 times)

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Offline LABob

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WeatherLink Distorting Indoor Temperature?
« on: April 15, 2013, 10:12:26 PM »
My Vantage Vue Pro 2 console was displaying the same temperature as my thermostat and my Oregon Scientific thermometer for over a week before I installed a 6510USB. Since then the indoor temperature reads from 2 - 4 F higher than both of those thermometers. Has anyone else experienced this?

Offline Weather Display

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Re: WeatherLink Distorting Indoor Temperature?
« Reply #1 on: April 15, 2013, 11:38:47 PM »
its possible that the extra power drain of the USB connection is causing a bit more heat build up inside the console/close to where the sensor is
sort of thing
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Offline LABob

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Re: WeatherLink Distorting Indoor Temperature?
« Reply #2 on: April 16, 2013, 12:33:34 AM »
Unfortunately, that's what I believe is happening. I unplugged the USB cable and it had no effect, but removing the 6510USB from the console did. The temperature stabilized back to where it should be after about 20 minutes. Then I placed the logger back in the console and the temperature went back up. That's very disappointing to me. I expect more from a $1,000 piece of equipment. You'd think that the engineers would be aware of heat issues and would avoid placing heat sources near temperature sensors. Somehow they manage to run the console on 5V power without a heat problem, why not the logger?

I guess my only realistic option at this point is to find a cable that will allow me to mount the 6510USB outside of the console and still close the battery door.

EDIT - Does anyone with the serial version of the data logger notice that the indoor temperature slowly drops a few degrees after removing the unit from the console? Unplugging the data cable doesn't work to stop the heat with the USB version. It must be heat generated by all that hard work writing bits to NVRAM.
« Last Edit: April 16, 2013, 12:56:34 AM by LABob »

Offline tbern

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Re: WeatherLink Distorting Indoor Temperature?
« Reply #3 on: April 16, 2013, 12:59:22 AM »
could you just adjust the temp in your console to match your thermostat when everything is hooked up and running, then watch to see if they maintain the same temps over a few days time?  just a thought and easy to try.

Offline LABob

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Re: WeatherLink Distorting Indoor Temperature?
« Reply #4 on: April 16, 2013, 01:02:07 AM »
I was thinking about doing that, but I don't know how accurate those thermometers are. I only noticed that the Davis and the Oregon Scientific were within 0.1 F most of the time and all of the sudden they were way off. I suppose if the correction remains constant it's a viable fix. I'll give it a try and report back.

Offline LABob

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Re: WeatherLink Distorting Indoor Temperature?
« Reply #5 on: April 16, 2013, 10:13:32 AM »
So far it seems to be holding constant so the correction factor is working. I'll keep my fingers crossed.

Offline tbern

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Re: WeatherLink Distorting Indoor Temperature?
« Reply #6 on: April 16, 2013, 10:32:27 AM »
good to hear, never thought that hooking it up would affect the temp.

Offline LABob

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Re: WeatherLink Distorting Indoor Temperature?
« Reply #7 on: April 16, 2013, 10:47:19 AM »
I wouldn't have thought a designer would put a heat source below a temperature sensor. They could've designed it to be above the sensor and taken advantage of convection to make the indoor sensors even more accurate and responsive.

I know it's way overkill and likely to be inaccurate anyway, but my psychology needs to know that the thermometer is based on some logical reference other than another cheap electronic thermometer. I'm going to boil some distilled water and see what my mercury lab thermometer reads. I should be able to correct for local altimeter pressure to get the *real* temp and any correction factor needed on the lab thermometer. Then I can compare that with the Davis console.
« Last Edit: April 16, 2013, 10:51:48 AM by LABob »

Offline johnd

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Re: WeatherLink Distorting Indoor Temperature?
« Reply #8 on: April 16, 2013, 11:15:44 AM »
Easier to use a distilled ice/water mix and (hopefully) closer to your room temperature.
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Offline LABob

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Re: WeatherLink Distorting Indoor Temperature?
« Reply #9 on: April 16, 2013, 11:18:53 AM »
Good idea. Thanks for reminding me of the slushy ice water calibration. I'll compare both and see if the correction factor is constant.

Offline LABob

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Re: WeatherLink Distorting Indoor Temperature?
« Reply #10 on: April 17, 2013, 12:56:27 AM »
I learned something interesting: My old Radio Shack digital thermometer with probe is spot on. Made an ice bath in a vacuum insulated Thermos and placed the probe into the bath and got a 32.0F reading that held steady for 30 minutes. I've been trying to calibrate the Davis console with that thermometer, but it's tricky because the Radio Shack thermometer responds to changes in temperature almost immediately. If I even stand too close to the probe for more than 10 seconds or so, the temperature increases by 0.2. The Davis is much slower to respond. Since the inside temperature slowly changes, the Radio Shack thermometer picks up on those changes much faster. I've been dialing it in and seem to be zeroing in on somewhere around -1.6F calibration. I just wish I had another reference point to check the accuracy further up the scale.

Offline johnd

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Re: WeatherLink Distorting Indoor Temperature?
« Reply #11 on: April 17, 2013, 02:49:12 AM »
If an accurate inside temperature is important to you, have you considered using a wireless Envoy console rather than the standard one? Then you can attach an external temperature probe which would almost certainly give you a better figure.
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Offline LABob

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Re: WeatherLink Distorting Indoor Temperature?
« Reply #12 on: April 17, 2013, 10:07:00 AM »
It's not that important to me, but it is important to me that I've done what I can to make the instruments I have as accurate as I can.

Offline LABob

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Re: WeatherLink Distorting Indoor Temperature?
« Reply #13 on: April 18, 2013, 11:11:21 AM »
I got irritated trying to match the Radio Shack thermometer because it fluctuates too rapidly to get a fix. I calibrated an alcohol-filled glass thermometer and used that. I believe I have it pretty close.

Since the glass thermometer is only graduated in 2F increments, I snapped pictures of it and used Photoshop to make more precise measurements of the exact temperature. It turned out that the glass thermometer was reading almost precisely 32F in the ice bath, but 222 in boiling distilled water. According to the altimeter pressure at the time the water should have been boiling at 209.5F. Assuming that the 12.5F error was spread evenly between 32 and 209.5 told me that each 2F mark on the thermometer was actually 1.868F. When the glass thermometer read as closely to 70F on the spot as I could measure at the pixel level (somewhere around 0.1F) I set the Davis to:

Code: [Select]
(70 - 32) * (1.868 / 2) + 32 = 67.5
I then left the heat off overnight and repeated the measurement and calculation to compare with the console. The glass thermometer read very close to 67.75F and the console read 65.4F. Some quick math:

Code: [Select]
(67.75 - 32) * (1.868 / 2) + 32 = 65.39F
Perfect  :grin: Hopefully my logic isn't flawed here.

Offline LABob

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Re: WeatherLink Distorting Indoor Temperature?
« Reply #14 on: April 19, 2013, 10:34:47 AM »
It's worse than I had feared. The distortions caused by the logger aren't constant. After witnessing the same phenomenon with the glass thermometer it seems that where I thought the Radio Shack thermometer was fluctuating wildly turned out to be the Davis that was failing. Three different electronic thermometers and a glass thermometer are in close agreement to the temperature in the room, but sometimes the Davis console is spot-on, and then later it's off by a couple of degrees.

I called Davis and they're shipping out a new logger. I really hope that's the issue and not the console.

Offline dalecoy

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Re: WeatherLink Distorting Indoor Temperature?
« Reply #15 on: April 19, 2013, 11:29:03 AM »
It's worse than I had feared. The distortions caused by the logger aren't constant. After witnessing the same phenomenon with the glass thermometer it seems that where I thought the Radio Shack thermometer was fluctuating wildly turned out to be the Davis that was failing. Three different electronic thermometers and a glass thermometer are in close agreement to the temperature in the room, but sometimes the Davis console is spot-on, and then later it's off by a couple of degrees.

I called Davis and they're shipping out a new logger. I really hope that's the issue and not the console.

Just checking - do you ever use the backlight in the console?


Offline LABob

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Re: WeatherLink Distorting Indoor Temperature?
« Reply #16 on: April 19, 2013, 11:31:10 AM »
After reading that it would distort the temperature I've never used it.

Offline dalecoy

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Re: WeatherLink Distorting Indoor Temperature?
« Reply #17 on: April 19, 2013, 12:12:24 PM »
After reading that it would distort the temperature I've never used it.

Thanks. 

I'm sure you are taking a lot of care in your measurements, but you have not yet described (for the rest of us) any details.  How/where is the console located, where are you putting the other instruments, how do you assure that the "environment" of all of the instruments is the same, etc.

Also, you have said that all of your other instruments " are in close agreement to the temperature in the room", but you haven't said how you measure the "temperature in the room".

Offline LABob

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Re: WeatherLink Distorting Indoor Temperature?
« Reply #18 on: April 19, 2013, 12:24:12 PM »
After reading that it would distort the temperature I've never used it.

Thanks.  

I'm sure you are taking a lot of care in your measurements, but you have not yet described (for the rest of us) any details.  How/where is the console located, where are you putting the other instruments, how do you assure that the "environment" of all of the instruments is the same, etc.

They're all located within a foot of each other at the same height and all sensors are positioned within one half-inch of the wall. That they substantially agree is evidence of the similarity of their locations. The probability of finding three locations with different temperatures that just happened to correspond with each thermometer's error in such a way as to cause them all to agree is exceedingly tiny. Even the thermostat which is mounted about 6 feet away reads the same.

Also, you have said that all of your other instruments " are in close agreement to the temperature in the room", but you haven't said how you measure the "temperature in the room".

I'm taking it for granted that if three separate thermometers and a thermostat, all made by different manufacturers at different times and of differing construction (glass, electronic, and bimetallic), two of which were calibrated using ice baths and boiling water, all agree on a temperature, that it is reasonable to assume that is the correct temperature. It would be a coincidence of amazing proportions to have four inaccurate thermometers that just so happened to be positioned in a place with a temperature differential that was exactly equal to their errors, and to match each other, all with the wrong temperature.

I don't want to give the impression that they all read 68.0F in unison, and then 68.1F in lockstep. What is happening, though, is that they will read something like 67.8, 68.1, 68, and 68 while the Davis reads 71.
« Last Edit: April 19, 2013, 12:26:21 PM by LABob »

Offline dalecoy

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Re: WeatherLink Distorting Indoor Temperature?
« Reply #19 on: April 19, 2013, 12:33:05 PM »
Thanks for the details - I was confident that you were doing something like that - you just hadn't described it.

They're all located within a foot of each other at the same height and all sensors are positioned within one half-inch of the wall.

Is the console mounted on the wall?  (Attached to the wall)?

Are the other sensors attached to the wall in some way?

Offline LABob

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Re: WeatherLink Distorting Indoor Temperature?
« Reply #20 on: April 19, 2013, 12:36:35 PM »
The thermostat and the Oregon Scientific are mounted to the wall, as is the Davis console. The Radio Shack thermometer has its probe dangling about three inches off of the Davis console antenna. The glass thermometer is resting on top of the Davis console with the bulb about a quarter-inch from the wall.

EDIT - I guess it's important to keep in mind that removing the data logger from the console causes all of this issue to go away. The Davis then agrees with the others without setting any offset.
« Last Edit: April 19, 2013, 12:39:00 PM by LABob »

Offline LABob

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Re: WeatherLink Distorting Indoor Temperature?
« Reply #21 on: April 20, 2013, 09:12:48 AM »
I wish it had occurred to me to test the outdoor temperature before I called Davis. Coincidentally, the outdoor temperature shows the same tendency to be about 2 - 3 higher than the other thermometers. I checked during the dark hours before sunrise to make sure there wasn't any radiational heating differences, and placed all the thermometers/probes within a foot of the FARS. I'm disconnecting the data logger now to see if the outdoor temperature falls as well. If it does, there's a firmware/hardware issue with the console when a USB data logger is installed.

Offline LABob

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Re: WeatherLink Distorting Indoor Temperature?
« Reply #22 on: April 20, 2013, 02:41:02 PM »
The outdoor offset is independent of the data logger  \:D/

Offline LABob

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Re: WeatherLink Distorting Indoor Temperature?
« Reply #23 on: April 22, 2013, 01:30:48 PM »
You've probably never encountered a case of OCD like mine  :grin:

I have an Oakton Temp 340 datalogging thermometer on the way. The combined accuracy of the probe and thermometer is 0.26F. The plan is to set this up next to the ISS and console and log the temperature readings at the same interval. After collecting a few hundred data points I will plot them and calculate the offset necessary to create the smallest average error between the two. It will be interesting to compare the Davis readings with this high-precision instrument. I'm hoping to be pleasantly surprised.

Offline LABob

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Re: WeatherLink Distorting Indoor Temperature?
« Reply #24 on: May 05, 2013, 05:21:57 PM »
OK. It took a long time to get to it, but Davis has been a real help so far. First they sent me a new 6510USB. When that didn't clear up the issue, they sent a new console. That doesn't clear the issue either. Two consoles and two data loggers with the same issue. I eliminated Meteobridge as the culprit by reproducing the results with WeatherLink. Here's what I know so far:

  1. Reading data from Connecting a 6510USB on a Vantage Pro 2 console to an active USB port on a computer/router
     affects the indoor temperature readings by a degree or two, usually in the upward direction.

  2. Extended experimentation shows that plugging the data logger into the console by itself does not cause the issue. It is only
     once the logger is being read often as Meteobridge-like devices would, or with Weather Bulletin running on WeatherLink. It
     is only when the data logger is connected to an active (powered) USB port on a computer/router.

Both consoles have 3.12, and the same day I first received the data logger I upgraded from 3.0 to 3.12 so there was never a time I tested a 3.0 firmware with this issue. I don't know if the hardware is any different, but both are "green dot" consoles.

Can anybody with a green dot console and 3.12 firmware reproduce this? If you want to follow my steps:

  1. Have another thermometer handy for reference. Take note of how it reads compared to the console
     over a period of time and note the offset (if any). It's important that both the console and the thermometer
     are as close as practical.

  2. If your data logger is being read through a 6510USB on a frequent and regular basis connected to an active USB port,
     disconnect the cable; if your console isn't being read on a frequent and regular basis if your data logger is not connected
     to an active USB port, connect it now.

  3. Wait at least 30 minutes and compare the temperature to the reading from Step 1, and also to the reference
     thermometer. If you are experiencing the issue, your indoor temperature will have changed by anywhere from
     0.8 to 2.0F (usually higher when connected to an active USB port). If you watch the console for an extended
     period (days), you may notice that the error value drifts slowly between 0 and 2F.
« Last Edit: May 05, 2013, 05:57:32 PM by LABob »