Help out a new guy?  - Page 1
Forum section: electronics / general

author: mike24
author_rank: Newbie
timestamp: May 24, 2021, 10:15:28 pm
content: New guy here. Hoping you experts can help me out with some beginner questions for my project.I want to mount a thermal image camera in a fixed location that will connect by wifi or bluetooth to an ipad or phone. It will then live feed thermal images to an app for constant thermal analysis.It should have enough resolution to pick out water that is suspended in air.What camera should I buy?Thanks,Mike

author: bob91343
author_rank: Super Contributor
timestamp: May 24, 2021, 11:41:04 pm
content: Google the subject and send email to a few companies that make what you want.

author: DaJMasta
author_rank: Super Contributor
timestamp: May 25, 2021, 03:47:04 am
content: Water that is suspended in air? You want a thermal analysis of a cloud, or like aerosolized droplets?I personally don't really know of either, but if you elaborate on what size particle you're trying to look at and what field of view you want and we can probably tell you if it's feasible. Generally droplets big enough to see with your eye are just going to look like reflections of the scene, so you'd probably be best off with a hot element somewhere out of the field of view of the camera and then look for the reflections of it in a camera - in this case framerate may actually be critically important (60Hz may be enough, but maybe just detecting presence of droplets as streaks would suffice). If you're trying to see clouds, you can with a standard lens at a long focus distance, but to see low temperature/not visible clouds you'd need something fancier than your uncooled bolometer if you even want a chance (and I don't know of this as an application).If you're trying to see microscopic droplets, well you're going to need an extremely narrow field of view and a lens to give you that, and I don't even know if that's a realistic expectation. If you want realtime fine particulate monitoring you'd probably want an array of screens or something for the particles to collide with, then watch the temperature of the screens for the evaporative cooling effect, though that's probably going to demand a very high sensitivity camera unless you have a lot of suspended water and a fairly dry ambient humidity.I guess a shorter answer is: we need a lot more details to really advise, but you may be trying to see something that's not realistically a good choice to see with thermal.

author: Fraser
author_rank: Super Contributor
timestamp: May 25, 2021, 10:26:26 am
content: Mike24,Before looking for a camera you really need to Research the thermography of water vapour in air as it is not a simple task and the results are not always what you expect. The success of such an approach can be very dependant upon the exact scenario, hence why other commenters are asking for more detail. Once you know the challenges of imaging water vapour in air, you will also learn about the required performance of the thermal imaging camera and the best test configuration to collect the required data. Try Googling “Thermography of water vapour”, “Thermal imaging water vapour” and “Thermal imaging steam”. That should reveal some research papers for you to study.It is worth bearing in mind that sometimes you have to create a specific set of conditions that will reveal a gas or liquid on a thermal imaging scene rather than operating in a purely passive monitoring mode. Examples are heating of a background plate to create background illumination and contrast or cooling of the background to increase contrast of the activity in the foreground. Thermal imaging of Water vapour is very different to imaging a bowl of water or ice.Once you know the specification of the camera that you need, you will better understand the financial implications of your test setup and will also discover whether such cameras can provide the remote monitoring that you desire. Remote monitoring can often be added to a system using an embedded computer acting as a remote controlled host and broadcast unit.Fraser

author: mike24
author_rank: Newbie
timestamp: May 26, 2021, 02:17:39 am
content: Thanks for the replies my friends.The target water droplets will be between 200-400 microns in size. The target distance will be 10-15 feet.It will be measuring the spray mist left behind a piece of machinery. Measuring if it is present or not. And also measuring roughly how much is present when compared to nothing at all.Is there a camera that can do this?Thanks,Mike

author: Fraser
author_rank: Super Contributor
timestamp: May 26, 2021, 10:48:38 am
content: I would not use a thermal imaging camera in this application. It is more complicated and expensive than it needs to be. My first thoughts were of a ‘path loss’ laser beam based detector that monitors the attentuation created by the presence of the water mist. This is a common ‘presence and performance’ test system for oil mist systems in industry. I suggest you contact some oil mist monitoring manufacturers or agents to see whether they can offer a system suitable for water mist detection and monitoring. It would be a far simpler and more reliable monitoring system than a thermal imaging camera.Try talking to this company about your needs....https://www.ribble-enviro.co.uk/product/g26-ambient-oil-mist-detector/The other option is to fit a flow sensor on the water pipe that feeds the misting nozzles. Any changes in the flow may be monitored and loss of flow would indicate loss of mist output. Increased flow could indicate a missing nozzle or leak in the nozzle side of the flow sensor pipe work. Very cheap and simple but with no monitoring of the mist cloud coverage so an obstruction between the mist nozzles and target area would not be detected.Fraser

author: mike24
author_rank: Newbie
timestamp: May 26, 2021, 01:23:34 pm
content: Hmmmm, oil mist sensor wont work because it needs a reflector plate mounted. No way to mount that downwind of the drift we are trying to measure.Flow sensor I already have multiple on the machine for the rate control. I am not trying to measure the flow with this idea. I am trying to measure the percentage of the flow that ends up in the air vs how much goes down on target.A picture of the mist behind the machine is attached.No way a thermal camera will work for this?Any other ideas?Appreciate the help.Thanks.

author: Fraser
author_rank: Super Contributor
timestamp: May 26, 2021, 02:51:34 pm
content: Hmmm this is like problem solving through a pinhole... not enough visibility of the situationNow that I know more about the scenario I can see that I was wasting my time with the sort of mist detection systems with which I am familiar.You need to provide full detail of the scenario in order to gain useful responses... some that come to mind are1. What exactly are you trying to achieve ? You originally asked about mist presence detection, now it seems to be mist coverage and fluid deposition.2. What is the temperature of the water/chemical spray ?3. What will be the temperature differential between the liquid and ambient air ?4. At what angle will the spray cloud be monitored... above, in front or to the side of the cloud. This effects the background contrast.5. Why do you need such a system... have you currently got a problem to solve or is this just ‘blue sky thinking’Fraser

author: DaJMasta
author_rank: Super Contributor
timestamp: May 26, 2021, 03:35:06 pm
content: Is this something that needs to be continuously monitored, or just checked? If it only needs checking you can probably load up the solution with an appropriate indicator and visualize it, put down fabric/paper as a test target, or even use an array of collection containers moved around to map out the spread.Unless the liquid being dispensed is significantly hotter or colder than the outside environment, it's not going to show up on a thermal camera - they are often used for seeing through some fog and particulate, so the best you could hope for for measuring a cloud of particulate would be measuring secondary effects, i.e. evaporative cooling. Now if you had the camera on a drone following your sprayer and did it during the night, you would definitely be able to see the effect against the background, but the energy from the sun and shadowing losses would mess up daylight measurement and there would be a point that the surface is saturated and the change in temperature with more liquid would no longer be present. Of course then ambient temperature, humidity, and wind speed is going to effect each individual measurement, and you'd have to do a lot of analysis and calibration to try and convert a cloud concentration into degrees of cooling on a target - possible, sure, but way more complicated than you probably want.I agree with Fraser, I don't think a thermal camera is right for this application, especially if you can't conduct your experiments in a test chamber or with test liquid where you could control some of the many variables and improve visibility in the LWIR band.

author: Fraser
author_rank: Super Contributor
timestamp: May 26, 2021, 05:05:21 pm
content: I just did some of my own research on the topic of spray chemical application in agriculture. This is an area where there is some serious development work going on. Trimble have an intelligent system that sprays only weeds and not bare soil (saving on chemicals cost), there are drones for both spraying and spray coverage monitoring. This is an area where farmers appreciate the money that can be saved by efficient application of fluids on their fields with minimum waste. Anyone developing a novel solution should expect to be suitably rewarded.I can see why the OP has an interest in such a topic but I do not see the thermal imaging camera as the solution he seeks.

author: mike24
author_rank: Newbie
timestamp: May 27, 2021, 04:00:43 am
content: My thinking is that the water droplets in the air should be a different temperature than the air itself. Water is a terrible store of energy and it should be cooler, if even slightly. What I want is a Thermal camera that can pick up this temperature difference and constantly send feedback to an app I have developed. The data does not have to be perfect, just close enough to compare. Maybe a thermal image camera that can do this does not exist yet?

author: DaJMasta
author_rank: Super Contributor
timestamp: May 27, 2021, 04:35:23 am
content: Especially with cooled cameras, you can see very fine temperature gradations, but what would make the water cooler than the air? If it's chilled or heated, sure, you can probably see that, but if you take ambient temperature water and put it in ambient temperature air, you are relying on evaporation to cool it down below the air temperature, and when it's dispersed in a cloud, that both doesn't happen linearly (the more water vapor in the air, the slower the rate of evaporation), it doesn't happen quickly (the air around the droplets gets saturated and then the interior of the cloud stops evaporating), and it can be dramatically increased by even small breezes.Water actually has a much higher thermal mass than air, it just also has a higher thermal conductivity, so the feel of it is cooler (because it wicks heat away from you faster than air does), but it changes temperature considerably slower because the a given volume of water takes a lot more energy to raise or lower the temperature than the same volume of air.It's not really that a thermal camera couldn't see something, it's that what you're seeing would be very difficult to quantify and would vary wildly given normal outdoor conditions. If you were doing this in a controlled indoor environment gleaning meaningful information from the images could probably happen, but you are going to have to do a massive amount of realtime compensation for exterior factors to get even mediocre data, and you're going to have to do a lot of modeling and experimentation to even figure out all the factors you need to compensate for.If you're looking for a pass/fail on whether the water is spraying or not, sure you can probably do that with an off the shelf camera in most conditions..... but you can get that with a visible camera. If you're trying to see residual amounts long distances from your source, the tiny volume of water suspended for longer terms in an increasing volume of air mean the millikelvin level temperature differences of the volume get harder to detect, and since it's now mostly water vapor in air, its emissivity is almost nothing and will be mostly transparent in thermal bands. To see water specifically, you'd need a detector that can look in the water absorption band (like 5-8um), a filter to make sure it's not detecting outside of that, and a bright enough illumination source in that band to offset losses from the naturally occurring humidity in the air, which in the case of in-the-field measurements could be as high as 100% humidity... and while it seems this is possible in some way with lasers (I think in a different band), I don't know of a commercial or industrial product available specifically for aerosol water detection.

author: mike24
author_rank: Newbie
timestamp: May 27, 2021, 04:57:37 am
content: The app has the ability to read an ambient temp sensor and compare it to the temps that thermal image sensor would send. I just need to decide what thermal image sensor (if any??) to use. The ambient temp sensor should get rid of a lot of the external factors? I could also program in another water temp sensor that would measure the temp of the spray solution in the tank or boom.The thermal image cam would then only need to identify and differentiate 2 different temperatures. The ambient air temp and the temp from the water sensor. What i want to identify is what percentage of what the camera is seeing is the ambient air temp and how much (if any) is the temp of the water droplets suspended in the air.If I know what temperatures and the difference I am looking for, I should be able to find a thermal image camera that could accomplish this task? Maybe I am over thinking it? Or underthinking it haha.

author: Vipitis
author_rank: Frequent Contributor
timestamp: May 27, 2021, 09:33:30 am
content: Since air is not really emitting but mostly transmitting the relevant radiation. You can't measure the ambient air temperature with a thermal camera that easily. What you see is emission, so surfaces that give off radiation. .I suspect that you will end up with a blurry image due to the sheer number of droplets and their motion. Unless you end up with a really really high resolution and low time constant system (basically a high end cooled research camera), you won't be able to see much. You would most likely get the average temperature from the whole fov with a radiometric uncooled Sensor which will be cheaper. However there are many limits to how accurate the numbers are, in absolute.From what I remember with water and uncooled microbolometers, is that water can end up looking a bit reflective, so it might give you the really cold sky back if no clouds are present. Or it will just scatter the radiation and give you a blur of reflectors temperature.If you were to fly a camera above the field, I am sure there would be a visible trail of whatever you are spraying, but I doubt the numbers you might get out of it are any useful.Since you are working with a system in motion you want to try something with a high framerate and low thermal time constant. At least 60hz to even have a chance. And you also want a radiometric core that's calibrated with a lens that is calibrated and has the correct field of view and depth of field.If this is a one off research project, you may just go out and rent a high end cooled unit with the infrastructure to run it and record data. But if you want to develop this into a permanent solution, I doubt you end up putting a 90k$ camera there just for some rough estimates.

author: mike24
author_rank: Newbie
timestamp: May 27, 2021, 02:34:49 pm
content: Do not really care what the image looks like. it will never be shown on the app. I want to convert the temp data over to a bar graph or gauges that will show how much of the chemical is escaping by drift or how much is landing on target. The end goal is a spray drift loss monitor that alarms the operator if his chemical is drifting off target or not.Maybe the thermal image camera is not the right sensor for this application? 90 k sounds way too pricy. It would never sell. Budget for the sensor will be around 1500-2000.

author: geggi1
author_rank: Frequent Contributor
timestamp: May 27, 2021, 11:23:29 pm
content: You should look in to a gas-line detector. These are made to detect minute amount of gas in the air and work by refraction of a laser beam. There are probably detectors working the same way on water.Look into companies like Yokogava and Emerson and what they might be able to supply.

author: bap2703
author_rank: Regular Contributor
timestamp: May 28, 2021, 09:22:11 pm
content: What you want is to look at the aerosolized droplets, not the vapour: that's too hard since sensors are especially designed not to see it.Try to get a look at that guy's papers:https://www.spiedigitallibrary.org/profile/Zhongwei.Chen-106166

author: CatalinaWOW
author_rank: Super Contributor
timestamp: May 29, 2021, 04:38:07 am
content: I believe prior posters are conveying their own experience in the field which my own experience validates. You can image this vapor under a variety of conditions, but there are always some conditions which make it invisible (zero contrast with be background) and using the image to quantify how much is there is even more difficult.Some things to think about:1. You used what appears to be a visible image to illustrate your problem. Why not use visible with an illuminator?2. Extending from 1, you could arrange to illuminate different regions at different times giving more information to separate background from signal.3. LIDAR systems could observe the backscatter from your mist spray. Use of short pulse widths allows range measurements and a powerful tool to separate ground returns from the mist you are trying to observe. Most LIDARs are optimized to find solid objects in a clear medium. Some adjustments will be required to observe a backscatter field. You will in fact be trying to utilize what most systems spend lots of time and energy to suppress and ignore.4. Scattering is strongly wavelength and particle size dependent. Using narrow band observation and/or illumination in more than one band can give rich information about the field.5. Fog is of great interest to mariners and aviators and fog detection and characterization systems of many types have been developed. Looking into these may find you something suitable for your use or give you some ideas.

author: Ultrapurple
author_rank: Super Contributor
timestamp: June 03, 2021, 08:22:39 am
content: As CatalinaWOW says, there is plenty of published work on this sort of thing. The idea of using range-gated imaging is not new and has been well developed; if you could make fast-enough light pulses and achieve fast-enough camera gating then you could build a very accurate 3D model of the spray/mist area.