Thermo Camera and iridescence, a structural colours

[Samuels-art]

Dear PF,

I am hoping you can help. I am trying to test the the speed that a beetle heats up under standardized conditions. I have buried a small container in crushed ice and place a beetle and thermometer inside. I wait until the thermometer and has reached 0°C, the idea then is to increase the the temperature with a heat lamp measuring the speed that the beetles heats up and resumes to forage.

I measure time, temperature and behaviour.

Now my problem is the relatively large differences between with the actual thermometer temperature and the reading I get with the thermo-camera (Model FLIR Systems, InfraCAM (Not the newer SD version)).

I have attached a .jpg showing the differences, where the 'Temperature' is recorded as the reading from the thermometer, the 'probe' is recorded as the thermometer probe in the ice chamber and the 'beetle' is the temperature of the beetle. X axis is the time in mins (at 20mins I moved the light source closer and you can see the sharp increase in temperature). The Y axis is the temperature in degrees Celsius.

I think the extra temperature is either a fault with the camera or some kind of reflected heat getting reflected from the beetle elytra (hard out 'shell' of a beetle). I mentioned iridescence and structural colours in the title. I did this because the beetles I will be using for the experiment will be iridescent. I wanted to ask if anyone knows of any pitfalls I may have when trying to measure temperature of a structural colour that is in a convex shape.

Kind regards and many thanks in advance.

Samuel Waldron

 

[Andy Resnick]

<snip>
Now my problem is the relatively large differences between with the actual thermometer temperature and the reading I get with the thermo-camera (Model FLIR Systems, InfraCAM (Not the newer SD version)).
<snip>

This is not surprising- the thermometer records temperature by responding to heat, while the camera records temperature by responding to the amount of light *and assumes the object is a black/grey body*. Clearly, the shell of the beetle is neither.

It's not clear from your description what object the thermometer is measuring- the container or the beetle? Can you use the shell temperature as a proxy for 'the' beetle temperature?

You have at least two options- instrument the beetle with thermocouples, or calibrate the camera using (perhaps) a dead beetle. Also, since you are radiantly heating the beetle, the thermocouples/camera should not be directly exposed to the lamp illumination.

 

[Samuels-art]

Thank you kindly for your reply. Sorry it has taken so long to get back to you.

The thermometer is measuring the ambient temperature in the chamber. Unfortunately we can not use thermocouples. The problem with calibrating the camera is that it auto calibrates. So it does not allow calibration on a specific thing. Also very frustrating as it can calibrate during a replicate.

Lastly, how is it possible that the camera is not exposed to the light source? Do you mean I should turn the light off before measuring?

Kind Regards and again sorry for the speed of my reply and me thanking you for the help.

Samuel Waldron

 

[Drakkith]

Lastly, how is it possible that the camera is not exposed to the light source? Do you mean I should turn the light off before measuring?

I'd try this and see if it does anything. It could be that reflection of the light source is messing with your camera.

 

[Samuels-art]

Yea I had previously considered this, however the calibration is automatics and apparently does it regardless every 30 seconds or each minute.

I am using the FLIR Systams InfraCam 250. Has anyone had any experience. I can find no information about calibration on the internet. I find this very strange!

 

[Drakkith]

Well, regardless of the calibration issue, I'd take a few pictures with the heating lamp off and see if it helps at all.

 

[Samuels-art]

Just tried, there seems to b little to no effect. However, to guard against it I have managed to find a ceramic bulb emitting only heat. It is used for terrariums, I will use the ambient light, two diffused strip lights to guard against reflection.

Just a side note, when I point the gun at the window I can see my body heat reflecting in it. Is this the same principle as the reflected heat from the light in the beetle elytra (shell!).

 

[Samuels-art]

P.S. I never said before, but thank you for the replies and help. Regards

S.

 

[Drakkith]

Just tried, there seems to b little to no effect. However, to guard against it I have managed to find a ceramic bulb emitting only heat. It is used for terrariums, I will use the ambient light, two diffused strip lights to guard against reflection.

To be clear, when I said "light", I meant IR radiation that your sensor detects. I thought your heat lamp emitted only IR radiation.

Just a side note, when I point the gun at the window I can see my body heat reflecting in it. Is this the same principle as the reflected heat from the light in the beetle elytra (shell!).

I believe so.

 

[Samuels-art]

To be clear, when I said "light", I meant IR radiation that your sensor detects. I thought your heat lamp emitted only IR radiation.

Hence no difference when the light is on or off! ;)

I'll let you know how it goes if you are interested. Hopefully the method will work tomorrow :)

Thanks again