Author Topic: Anyone have an estimated emissivity for the IVAC 9000 radiators?  (Read 168 times)

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Offline globoy

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Anyone have an estimated emissivity for the IVAC 9000 radiators?
« on: February 23, 2021, 06:06:43 pm »
This forum is really fantastic.  I am following in Frasier's 2018 footsteps to try to make some DIY blackbody radiators for learning and then to see if I can characterize and possibly improve the accuracy of a camera I have designed.

I got an IVAC 9000 from ebay and have been playing with it.  It seems to be operable.  It warms up, displays the "Check Ready" status and seems to hold stable temperatures.  I put my Agilent's K-type thermocouple into a screw hole next to the device's temperature sensor and my Lepton 3.5-based camera so the radiator fill's the camera's field of view.  This lead to some questions I am hoping someone here has experience with.

1. The device's instructions say an in-ear temperature probe being calibrated should read 26.0°C (+/- 0.3) for the low side and 38.0°C (+/- 0.1) for the high side.  My DMM shows 24.3°C for the low side and 36.5°C for the high side.  I realize that my meter has an error band and I may not be making ideal contact with its temperature sensor, but should I expect that the metal radiators are 26 and 38°C if the unit is working properly?  Or is it possible that the IVAC thermometer's somehow adjust what they read to really reflect the in-ear temperature.

2. What estimate should I use for the emissivity of the coating on the radiators?  Could I re-coat them with a paint for which I know the emissivity?

Below are images of my setup and the output from the Lepton peering at the low temperature radiator.

Thanks.
 

Offline _Wim_

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Re: Anyone have an estimated emissivity for the IVAC 9000 radiators?
« Reply #1 on: Yesterday at 07:50:31 pm »
According to this paper (https://www.tandfonline.com/doi/abs/10.1080/19315775.2014.11721683) the emissivity for such a calibrator was 0.972. The emissivity of the ear canal is apparently 0.9988 according to a reference in this paper.

Tip: use sci hub to access the full paper if desired. 
 
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Offline globoy

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Re: Anyone have an estimated emissivity for the IVAC 9000 radiators?
« Reply #2 on: Yesterday at 09:05:22 pm »
Thanks for that information! 
 

Offline bap2703

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Re: Anyone have an estimated emissivity for the IVAC 9000 radiators?
« Reply #3 on: Yesterday at 09:22:52 pm »
1. The device's instructions say an in-ear temperature probe being calibrated should read 26.0°C (+/- 0.3) for the low side and 38.0°C (+/- 0.1) for the high side.  My DMM shows 24.3°C for the low side and 36.5°C for the high side.  I realize that my meter has an error band and I may not be making ideal contact with its temperature sensor, but should I expect that the metal radiators are 26 and 38°C if the unit is working properly?  Or is it possible that the IVAC thermometer's somehow adjust what they read to really reflect the in-ear temperature.

The ear conduct should be quite close to a blackbody : made of water + it's a cavity.
It means that when you measure the temperature in the ear, you expect a blackbody. So to calibrate an ear thermometer you do it against a blackbody simulator.
Conclusion: your device should be at 26°C and 38°C and the emissivity pretty close to one.
Error most likely will come from the temperature measurement/regulation electronics.

Maybe you can rent a calibrated infrared thermometer to have another measurement and conclude which of your thermocouple measurement or your blackbody simulator isn't accurate.
 

Offline globoy

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Re: Anyone have an estimated emissivity for the IVAC 9000 radiators?
« Reply #4 on: Yesterday at 09:47:37 pm »
The ear conduct should be quite close to a blackbody : made of water + it's a cavity.
It means that when you measure the temperature in the ear, you expect a blackbody. So to calibrate an ear thermometer you do it against a blackbody simulator.
Conclusion: your device should be at 26°C and 38°C and the emissivity pretty close to one.
Error most likely will come from the temperature measurement/regulation electronics.

Maybe you can rent a calibrated infrared thermometer to have another measurement and conclude which of your thermocouple measurement or your blackbody simulator isn't accurate.

Ok.  Thanks for this too.  I will look for an accurate IR thermometer - probably see if I can borrow a good in-ear thermometer.
 


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