Infra Red Camera

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If you are looking for conventional photography with films or cameras sensitive to the infra-red spectrum see Infra-red photography

Infra red cameras, or "Thermal cameras" (especially the FLIR Ix series) are now being targeted at science education. What can be done with these, how easy are they to use and is the cost justified? The following article will try to show how these may be used to provide quick and visual experiments that either compliment or improve on traditional methods. Suggestions will also be made for more advanced work.


Background to this article

With infra red cameras now at prices comparable to a decent oscilloscope, and cheaper than some other single use kit found in schools, there may be a justifiable case for using these in science lessons. They give a clear, immediate and novel form of reinforcement of principles to the class. Of course, the camera may also find uses outside the science curriculum. It may be used in Geography, Art, D&T and may even save money by advising of building insulation requirements, fault finding on equipment circuits or detecting water ingress.


Buying Strategy

As with most new equipment, it is always better to have a trial or at least a demonstration of the equipment's potential and method of operation to judge suitability before buying. Many suppliers will offer a “try before you buy” option. However, if these are delivered to a department without a demonstrator, the results of the test may not convince you of what these cameras can do and how they may best be deployed. Similarly, too often technicians are often overlooked when externally organised demonstrations are performed , but they are relied on to get the apparatus into a “ready to go” format. The rest of this article should give some pointers to the effective use of these cameras in lessons or assessing a loaned camera.
The FLIR Ix range has three cameras which are offered. Do shop around as it is possible to pick up higher “spec'd” cameras for the price of the lowest “spec'd” camera from other suppliers. This is especially true for the "Educational Offer" FLIR have created with the I7. This offer is not tailored to the school market, but does offer lots of supporting documentation. It is only available to educational establisments. The higher pixel count of the I7 does give a better image for a target filling the frame or a wider angle at the same distance.
The supplied supporting software will allow more detailed analysis to be carried out, for example for Advanced level calorimetry work.



Before you start

A new unit will need 4 hours to charge. Treat the camera as a normal delicate camera and protect the lens.
Do observe the warnings in the manual, so no pointing lasers at it! The camera's range is limited so aim at targets in that range.
A brief guide to emmisivity (see Blackbody radiation )is all that is required to use the camera effectively. It is hoped that the later sections or links will explain the theory in an understandable format if required.
You are not dealing with light in the visible range, so things may not act as you would expect. Surfaces, especially metals and to an extent glass, become reflective. So beware the object you are looking at may be your own reflection! Conversely opaque materials may become transparent. A black bin liner is useful to not hide an arm is a useful demo. Also, unless your budget is exceptional, you are probably limited to a small screen and no external video output of the Ix series. Using a video camera focussed onto the camera's monitor with the output to a large screen will give a simple solution to class displays. Of note is that in poor lighting the auto-apperture of the camera may not give a good colour rendition. Putting a room light on will improve this. You will also have to note the surrounds for heat sources and sinks, spurious reflections and inadvertent transfer of heat by handling. Masking or insulation tape makes a good “common emissivity” target to compare different objects. See Leslie's Cube.
An dedicated area (free of spurious heat sources )where objects may be introduced is preferable to moving the camera.

Familiarisation

Perhaps the easiest thing to do with the camera is to see what your surroundings look like in IR. Five minutes of doing this will make life easier in the long run. So switch on and have a look around. Have a look at colleagues (notice that you can't see through their clothing -and this is reassuring for staff if you consider that these will be pointed at pupils). Hot water pipes heaters, computers, fridges and blinds are interesting targets. Look at windows and flat metallic surfaces paying attention to your position as a reflected object (flat metal rules are good). Take the camera out and point it at clouds, notice that higher clouds are cooler.
The camera will normally have different modes of operation. The default setting is usually best but, the other settings may be more able to show criteria looked for in a demonstration (for example heating above a threshold).
The Camera will click from time to time as it recalibrates the image. A surface is required to take readings from, although this could be as diffuse as a cloud!


Example uses

These are some suggested investigations and how to effect them. Readers are invited to add to this list. This is new technology and the possibilities of novel techniques is good, please share your ideas. The following ideas have are simple, quick to set up and are of minimal cost.
Although the resolution of the camera is better than 0.2C, the displayed temperature value will be determined by the nature of the surface being investigated. Accurate work means that either a different method of taking the temperature is used and the emmissivity of the surface is adjusted so the camera reads the "true" temperature or a strip of tape of known emmissivity is used as a coating. Effectively a calibration is required for each new surface.
The examples below use the "rainbow" scheme to show tempoerature differences. This is more popular than greyscale and is more vivid. For analysis the greyscale would be better.

Friction

Required set up
Camera pointing slightly downward to a secured block of wood with an indentation in the centre. Wooden dowel in a cordless drill.
Method
With the block of wood at room temperature introduce the dowel to the indentation. Turn on the drill and see the colour of the contact area indicate a temperature rise. This may be related to Count Rumford's work in boring cannon.
IRDrillPencil.jpg

Convection in water.

Required set up
Camera pointing near level at a thermally flat background. Conduction in water apparatus (circular tubing containing water with funnel at top) at room temperature placed in field of view of camera. It is suggested that thin walled clear tubing may be filled as an alternative and a “T” connector used to join ends and remove bubbles.
Method
Hold one vertical limb of the tube in your hand. After a few minutes the heat distribution begins to show.
IRconvection.jpg

Convection driver.

Required set up
Camera pointing to an already warmed "lavalamp".
Method
Take image and describe the hot base and cooler top cause the wax to become less and more dense than the bulk, so the warm wax rises and the cooled wax sinks. Although the walls of the lamp are opaque to IR , it should (just about) be possible to see a central warm dome at the base.
IRLava lamp.jpg


Cooling by evaporation

Set up
Camera pointing downward to a non porous insulating base. Water propanone and ethanol with pipette droppers in each.
Method
Drop small pools of each in turn and observe in camera. More volatile liquid is colder than less volatile liquids.
IRsolvents.jpg

This method can also be used to show relative volativities, as an example of properties of organics and adding the number of carbon atoms.
Method
A plastic drip tray or similar is placed on a flat surface.
The alcohols are waiting in test-tubes in a test tube rack, with a dropping pipette in each tube.
Randomize the order that each pipette is taken out and trace the initial letter of each onto the tray. After a few seconds the image should show a progression of lesser cooling down the series.
Volatilealcohols.jpg

Relative Humidity (one for the geographers)

Set up
Camera pointing at two identical porous targets (e.g. small blocks of balsa wood). Distilled water bottle and desktop fan. Method
Wash one of the blocks with distilled water and observe temperature change in relation to the second. After a few minutes take readings and note. Turn fan on. Use look up tables to compare aspirated (fan on) and non-aspirated values of relative humidity.

Conduction

The conduction rods supplied by Nichol, Philip Harris and others where thermochromic film is applied to the surfaces works nicely with a thermal Camera.
Set up
Camera pointing at the conduction apparatus after it has been placed in a small quantity of hot water.
Note the link between the thermal film and the output in IR.
IRConductingRods.jpg

Leslie's Cube

Set up
Camera pointing at the cube turned so that two edges are presented. Masking tape placed low down over the edge and in contact with part of the two presented faces. Note that the shiny surface should not reflect any hot surfaces to the camera.
Method
Fill with hot water and replace cap. Note the masking tape shows same temperature, but the different emissivities of the surfaces shows different temperatures.See alsoLeslie's Cube

IRlesleyscube.jpg


Cooling by expansion

Set up
Camera pointing at can of “Dust Off” (Rapid online code 87-0660 ~£6 for 200ml [1] ) This seems to give the best results of cans tested.
Method
Depress the button on the can for about 1 minute. Notice the temperature of the nozzle and can.
The level of the propellant will be obvious after few seconds
IRCan.jpg

Exothermic reaction (Hydration of sodium hydroxide)

Set up
Camera pointing downward to a petri-dish containing a few mm of water. Single pellet of sodium hydroxide, pair of forceps for delivery.
Method
Place the pellet into the centre of the dish and observe changes.
IRexothermic.jpg

Endothermic reaction (Hydration of ammonium chloride{or citric acid with bicarb})

Set up
Camera pointing downward to a petri-dish containing a few mm of water. Small quantity of Ammonium chloride, spatula for delivery.
Method
Place the chloride into the centre of the dish and observe changes.
IRendothermic.jpg This demonstration also works well with a solution of citric acid into which crystals of sodium hydrogen carbonate is placed. This has the advantage as there is a chemical reaction and bubbles are seen to be produced.

Huddling penguins

The camera can be thought of as having loads of non-contact thermometers, (an I7 can be thought of as having 1n array of 140x140 temperature sensors: imagine the cost of thermometers!).
Set up:
A collection of (ideally rimless) test-tubes held together with a few elastic bands. Camera pointing downward to where the tubes will be studied. Plentiful supply of hot water and a bowl to hold. A roll of masking tape (or similar) can be used to act as a stand.
Method:
The tubes are filled with hot water, but kept in the bowl surrounded by hot water until all are filled. When all are filled the tubes are removed and placed under the camera.
Image after a few seconds
A still is then taken (for later reference).
After a while a second image is taken (Five minutes should suffice).
The inner tubes should be significantly warmer than the external ones. If a fan is available the effect of wind can also be investigated.
Image after about 5 minutes
If time allows a third image may also be used.
after many minutes

National Grid

Set up
Requires a demonstration of step up and step down transformers. The method uses 2V ac and a pair of 10:1 transformers. Camera pointing to identical exposed 15 ohm high wattage resistors.
Method
The apparatus is set up so that two 2.5V mes Bulbs are powered either by the same ac supply (Westminster kit) or as two different circuits. One branch or circuit should be direct to one bulb, the other via a 1:10 step up followed by a 10:1 step down transformer.
On switching on both lamps are of similar brightnesses.
IF a 15 ohm resistor is placed in each circuit between the power supply and bulb in the direct route or in between the two transformers on the stepped supply a noticeable change in intensity is noted on the direct (low voltage side).
Looking at the two resistors the heat given out on the Low voltage version is much greater than that on the High voltage side. Caution: ensure that the transformers are step up and step down.
NationalGridResistor.jpg

Heating of the Earth

A model globe is heated with a radiant heater (an Infra red heat lamp worked well or a spot lamp, less so).
As the globe wams the parts at 90 degrees to the lamp heat more than those at an angle. Be careful not to place the lamp too close!. Turning the globe slowly for a few minutes will give a warm equator or tropic area. Switch off and move the lamp so as to avoid reflected heat confusing the image.
If the globe is mounted at a 22.5degree angle, the Arctic and Antarctic permanent light/dark can also be illustrated. The Polar summer is still cool due to the angle.
version having been turned and lamp switched off

Who has bird flu?

Set up NOT TESTED
Change the camera settings to show “area above” temperature Camera pointing so that pupils can move into shot. A hot towel.
Method
Using a volunteer set the camera to their forehead temperature. Get a few volunteers to pass infornt of the camera. One volunteer should be “infected” simulated by holding towel to head before going into shot.

Cold vs warm blooded

If school has mammals and reptiles these can be looked at with the camera.


How long has a body been left? As a Forensic topic

Note the temperature of a bottle of water.
Compare the target to a recently left identical bottle of water at 37C. Monitor the cooling of the control and plot a graph of temperature against time. Note will depend on room temperature and graphs can be drawn beforehand.

Things that don't work (yet).

Showing IR is an EM wave through polarisation. Normal polarising filters are opaque to IR. It was thought that using the “brewster angle” polarisation could be demonstrated, however, a suitable polarising filter is of comparable price to the camera.

Things that won't work

Showing a remote control a source of infra red (using an IR L.E.D.). The L.E.D. works in the order of 850nm (near infra red). The camera has a window around the 10 micrometer mark.
You are far better off using a normal camera, for example on a mobile phone.

More advanced suggestions.

As advanced level work the non contact nature does have all sorts of advantages for project work.
The supplied software allows for more detailed, and quantative work to be carried out.
Work may range from comparing emmisivities of different finishes (D&T), possibly an alternative to heat conduction work (Lee's disk type arrangement for example), heat flow, mechanical work heating, leidenfrost effect, energy absorption (e.g. ballistics), choice chambers and other environmental work, calorimetry etc.
OCR Advanced Level Physics Specification B (Advancing Physics) has a whole section on imaging and another on sensors. This is ideal for the the course.For example, the image for the I5 is 100 x100 pixels so 10,000 pixels, grey scale images can be used to give a bit per pixel value so that the image size can be calculated. Resolution (0.1C), frame rate, field of view all given in the specification can be investigated. See www.flir.com/cs/emea/en/view/?id=41963.



Acknowledgements

In preparing this article the website of the (Concord Consortium [2]) and Barry Hawkins of Dataharvest proved useful ( Barry demonstrated the FLIR I7 at a Technician's CPD event in Hinckley ). Barry has some applications that will be placed on the (Dataharvest website[3]). FLIR [4] also have lots of resources but tend to be aimed at industry. Their videos and case studies are good reading. Hopefully any duplicated work is using a different approach.

--D.B.Ferguson (talk) 12:17, 25 August 2012 (BST)

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