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Wireless communication from multiple temperature sensors - Interested?

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  • JamesVorn
    replied
    I have watched this video. Nice information and thanks for sharing. I will share this informative video with everyone.

    Leave a comment:


  • Julian Jameson
    replied
    I programmed some updates into the Android app this weekend and made a video to demonstrate them.

    If you would like to take a look, the video is here: https://www.youtube.com/watch?v=r2Kt0Epz664

    Leave a comment:


  • J.P.M.
    replied
    Originally posted by SunEagle View Post
    Based on how you described you temperature data gathering procedure I figured you were using that type of thermometer and that you were using it correctly. Those thermometers are pretty accurate if you use them as close to the target as possible.

    The camera I was referring to is made by FLIR and I guess I got carried away with explaining how they work.

    Sorry for any confusion to anyone reading my posts.
    Understood. Thank you. I'm not as confident of the thermometer's accuracy as I am of the attempted consistency of my measurement methods and thus the precision of measurements, one 10 day period to the next.

    Leave a comment:


  • Julian Jameson
    replied
    Hi Mike,

    Thanks for your reply. The Bluetooth module that is currently used in the device is Class 2 with "up to" 10 meter range.

    I did look into using other wireless modules such as the zigbee, but as you mentioned, they don't interface so easily with [all] common devices such as smartphones, tablets and laptops etc.

    Also, keeping the costs down, really is my main objective. I'm assuming that if the entire device (including wires, sensors, power supply and case) is more than $90-100, then it just won't sell. Even if it does include an Android app with community-driven upgrades!

    Julian

    Originally posted by Mike90250 View Post
    re the Bluetooth radio, is this the short range (10ft) or the longer range (40ft) ? Have you looked into zigbee radio (but that does not work with 90% cell phones?

    Leave a comment:


  • SunEagle
    replied
    Originally posted by J.P.M. View Post
    It's not a camera it's a thermometer with a digital readout.

    The aperture is right up against the back of the panel when measuring.
    Based on how you described you temperature data gathering procedure I figured you were using that type of thermometer and that you were using it correctly. Those thermometers are pretty accurate if you use them as close to the target as possible.

    The camera I was referring to is made by FLIR and I guess I got carried away with explaining how they work.

    Sorry for any confusion to anyone reading my posts.

    Leave a comment:


  • J.P.M.
    replied
    Originally posted by SunEagle View Post
    One of the areas they taught us in the Thermography course was to be aware of both wind and air moisture content when taking a reading with the camera. Since a lot of the readings would be done on High Voltage gear you didn't want to get too close to the gear so the temperature reading could be at least a couple dozen feet away from the target. The moisture content of the air between the camera and target could diffuse the heat being radiated out from the target which would lower the reading and not give you an accurate measurement. So fog would be a bad time to take IR readings if you wanted very accurate temperature measurements.

    With your dry environment and the distance between your IR camera and target you shouldn't have to worry about fog or air moisture.

    [FONT=Comic Sans MS]Maybe just spiders and wasps that want to live under your array.[/FONT]
    It's not a camera it's a thermometer with a digital readout.

    The aperture is right up against the back of the panel when measuring.

    Leave a comment:


  • SunEagle
    replied
    Originally posted by J.P.M. View Post
    One of the other things I think I observed pretty consistently is that any individual panel's temp. seems to vary by several deg F. over its surface - even between adjacent cells. What I try to do is measure at 4-6 random places over each panel and form an opinion as to what a representative temp. is. I'll be among the first to say that it's probably not as precise as 16 individual sensors - one/panel, but perhaps more representative of reality over the whole panel - hard to say. That's part of the variability - where engineering "science" becomes a bit engineering "art". I've thought about a more permanent setup. However, unless/until I can find a way to get a better SWAG at an "average" panel temp. and not just one cell in a panel, I'll stick with what I have for now at least, but I'm more than open to suggestions. It really is a bit of a PITA.

    As long as there is no moisture on a surface, I'm not sure how air moisture content will affect the measurement of a terrestrial surface, but I'm certainly willing to learn. Most of the time, when I'm measuring anyway, the air on that roof is about as dry as a popcorn fart.

    Air moisture content as measured/correlated by the dew point temp. probably has an influence on the effective radiant sky temp. needed for measuring array to sky rad. heat trans. as the copious literature will confirm, a lot of which I have copies and some of which I had a hand in.
    One of the areas they taught us in the Thermography course was to be aware of both wind and air moisture content when taking a reading with the camera. Since a lot of the readings would be done on High Voltage gear you didn't want to get too close to the gear so the temperature reading could be at least a couple dozen feet away from the target. The moisture content of the air between the camera and target could diffuse the heat being radiated out from the target which would lower the reading and not give you an accurate measurement. So fog would be a bad time to take IR readings if you wanted very accurate temperature measurements.

    With your dry environment and the distance between your IR camera and target you shouldn't have to worry about fog or air moisture.

    [FONT=Comic Sans MS]Maybe just spiders and wasps that want to live under your array.[/FONT]

    Leave a comment:


  • J.P.M.
    replied
    Originally posted by SunEagle View Post
    Yep. Wind velocity and air moisture content can both affect material temperatures and IR readings. You just have to be aware of the environment to understand how it affects your temperature data.

    As for a 10" crawlspace under the panels as being "safe".. that is where I would be looking for a more permanent temperature measuring device. But if you got the time then go for it. Just be safe doing it.
    One of the other things I think I observed pretty consistently is that any individual panel's temp. seems to vary by several deg F. over its surface - even between adjacent cells. What I try to do is measure at 4-6 random places over each panel and form an opinion as to what a representative temp. is. I'll be among the first to say that it's probably not as precise as 16 individual sensors - one/panel, but perhaps more representative of reality over the whole panel - hard to say. That's part of the variability - where engineering "science" becomes a bit engineering "art". I've thought about a more permanent setup. However, unless/until I can find a way to get a better SWAG at an "average" panel temp. and not just one cell in a panel, I'll stick with what I have for now at least, but I'm more than open to suggestions. It really is a bit of a PITA.

    As long as there is no moisture on a surface, I'm not sure how air moisture content will affect the measurement of a terrestrial surface, but I'm certainly willing to learn. Most of the time, when I'm measuring anyway, the air on that roof is about as dry as a popcorn fart.

    Air moisture content as measured/correlated by the dew point temp. probably has an influence on the effective radiant sky temp. needed for measuring array to sky rad. heat trans. as the copious literature will confirm, a lot of which I have copies and some of which I had a hand in.

    Leave a comment:


  • J.P.M.
    replied
    Originally posted by inetdog View Post
    It sounds like someone should give you a research grant.
    No thanks. Been there, done that in a prior iteration of life. I work alone and do what I want - not what someone else thinks I ought to be doing.

    Besides, paraphrasing a famous scientist, it takes time if I'm going to find out not only what nature is telling me, but more importantly what nature is whispering. People holding purse strings are not known for having a lot of patience for such pastimes. Screwum.

    For me, the race is over, the rats lost. I now get to bloviate, pretty much with impunity in places like this forum, and regale a few folks with salient wit/wisdom/mental spoor.

    Leave a comment:


  • SunEagle
    replied
    Originally posted by J.P.M. View Post
    It's not an exact science - or much science at all really. Being retired with more time than money and more money than brains affords me the opp. to buy things I've done without for 30 or so yrs. like a dedicated weather station and pyranometer 4 ft. from the array and some other stuff and fart around to my heart's content.

    The temp. readings get confirmed, if it can be called that, by doing an energy/heat bal. on the array. The eff. rad. sky temp. come from several empirical correlations from solar and meteorological journals and other open lit. stuff as well as some other methods I worked out. The view factors for solar reflectance and IR to/from the surroundings come from radiation heat transfer. The roof temps. under the array and the exposed roof are also measured w/the IR thermometer which is adjustable for surface emissivity (I'm a bit dubious about that accuracy, but so far the numbers seem to make some sense). The biggest unknown is the convection heat transfer and particularly the effects of the wind vector and its variability. So far, that seems to agree pretty well with a fairly large body of published stuff of varying applicability and accuracy on that sub aspect of convective heat transfer. Anyone who's done a lit. search probably knows what I'm talking about.

    The 44 - 48F. above roof amb. for the array temp. I mentioned is about as high as it gets under "full" sun with low wind velocity, but under those conditions it's not that uncommon. It's a ballpark # for a sunny day.

    I'd like to get a piece of the Sunpower glazing by itself and see if I can figure out if their magic anti reflectance coating affects glass emissivity in the IR region. So far my guess is that it does not, or at least not to the degree that my meager attempts can detect.

    The array has about 10+" of clearance under it allowing me to get under it in a snug but still safe (?) way for measurements. FWIW, the array top (sky facing) temps. are usually a couple of deg. F cooler than underneath the array under full sun. I would have thought different. It may have something to do with better convection/rad. heat transfer on top. Another blast of the obvious: the array temp. variation follows the wind direction with array temps. being lower upwind and increasing by about 2F. to about 6F. downwind along the way, depending on wind vector and variability. That seems to correlate quite well with the 10 min. ave. wind direction as recorded by the weather station - a Davis Inst. Pro 2 Plus.
    Yep. Wind velocity and air moisture content can both affect material temperatures and IR readings. You just have to be aware of the environment to understand how it affects your temperature data.

    As for a 10" crawlspace under the panels as being "safe".. that is where I would be looking for a more permanent temperature measuring device. But if you got the time then go for it. Just be safe doing it.

    Leave a comment:


  • J.P.M.
    replied
    Originally posted by SunEagle View Post
    I'm impressed. I wouldn't have thought the panels would be that much hotter than the roof but I guess since they get the sunlight and the roof is in the shade it would be at a lower temp.
    It's not an exact science - or much science at all really. Being retired with more time than money and more money than brains affords me the opp. to buy things I've done without for 30 or so yrs. like a dedicated weather station and pyranometer 4 ft. from the array and some other stuff and fart around to my heart's content.

    The temp. readings get confirmed, if it can be called that, by doing an energy/heat bal. on the array. The eff. rad. sky temp. come from several empirical correlations from solar and meteorological journals and other open lit. stuff as well as some other methods I worked out. The view factors for solar reflectance and IR to/from the surroundings come from radiation heat transfer. The roof temps. under the array and the exposed roof are also measured w/the IR thermometer which is adjustable for surface emissivity (I'm a bit dubious about that accuracy, but so far the numbers seem to make some sense). The biggest unknown is the convection heat transfer and particularly the effects of the wind vector and its variability. So far, that seems to agree pretty well with a fairly large body of published stuff of varying applicability and accuracy on that sub aspect of convective heat transfer. Anyone who's done a lit. search probably knows what I'm talking about.

    The 44 - 48F. above roof amb. for the array temp. I mentioned is about as high as it gets under "full" sun with low wind velocity, but under those conditions it's not that uncommon. It's a ballpark # for a sunny day.

    I'd like to get a piece of the Sunpower glazing by itself and see if I can figure out if their magic anti reflectance coating affects glass emissivity in the IR region. So far my guess is that it does not, or at least not to the degree that my meager attempts can detect.

    The array has about 10+" of clearance under it allowing me to get under it in a snug but still safe (?) way for measurements. FWIW, the array top (sky facing) temps. are usually a couple of deg. F cooler than underneath the array under full sun. I would have thought different. It may have something to do with better convection/rad. heat transfer on top. Another blast of the obvious: the array temp. variation follows the wind direction with array temps. being lower upwind and increasing by about 2F. to about 6F. downwind along the way, depending on wind vector and variability. That seems to correlate quite well with the 10 min. ave. wind direction as recorded by the weather station - a Davis Inst. Pro 2 Plus.

    Leave a comment:


  • SunEagle
    replied
    Originally posted by Mike90250 View Post
    re the Bluetooth radio, is this the short range (10ft) or the longer range (40ft) ? Have you looked into zigbee radio (but that does not work with 90% cell phones?
    Even if it is the short range Bluetooth you can use a booster to get the data to your wireless router. Once it is on the web then you just need the app to access it.

    Getting live temperature readings is useful data for different applications but how the "sensor" (thermocouple, RTD, etc.) is collecting the data is real important to the material it is attached to.

    A surface temperature measuring device has a number of efficiency issues due to compatibility of the sensor material and what it is attached to.

    An IR camera (not one of those little gun type that you just point and get a temperature reading) is a much better way of collecting real accurate temperature data as long as you have set up the camera for the correct material emissivity, the target is larger than the sensing "cone" area and it has a good "focus" of the target.

    While IR cameras were very expensive 5 to 10 years ago ($5k to $35k) they have now come way down in price to to below $1000 for a basic model. There are even miniature IR cameras used in the RC model industry that provide very good pictures even at night.

    Leave a comment:


  • Mike90250
    replied
    re the Bluetooth radio, is this the short range (10ft) or the longer range (40ft) ? Have you looked into zigbee radio (but that does not work with 90% cell phones?

    Leave a comment:


  • SunEagle
    replied
    Originally posted by J.P.M. View Post
    A labor of love. Takes about 8 min./ series. Start 12 min. before min. incidence angle, read/record monitor data, start 2d round of readings 4 min. later and finish 8 min. after that. Hopefully, temps. are symmetric around min. incid.. angle time. All needed for ongoing est. of panel fouling as f(time) - every 10 days til it rains and probably thereafter. Lots of interesting stuff along the way. So far ave. measured temps seem to agree +/- 2 F. or so with an algor. I conjured up. ( FWIW, depending on wind vector panel temps. about 44-48 F. higher than roof amb. which runs about 5-10F or so above ground level amb. Also, working on est. for wind heat trans. coeff.
    I'm impressed. I wouldn't have thought the panels would be that much hotter than the roof but I guess since they get the sunlight and the roof is in the shade it would be at a lower temp.

    Leave a comment:


  • inetdog
    replied
    It sounds like someone should give you a research grant.

    Leave a comment:

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