A little while ago I stumbled upon a cavity type Blackbody on eBay.com. The unit looked to be in good condition and was equipped with a useful 1" diameter cavity. Such cavity type Blackbodies present a >99% emissivity source to a thermal camera when testing measurement accuracy etc.
The price of the EOI Blackbody made it very tempting, even though it was located in the USA. I pulled the trigger and bought the unit. It took an awful long time to arrive thanks to eBay's new budget shipping program. Well thankfully the parcel arrived today
My first thoughts were that the parcel was not the expected Blackbody as it was so small ! I opened it and sure enough the box contained a Blackbody
I am so pleased with my purchase.... first impressions were good and this thing is soooo dinky
I thought the unit would be a lot larger than it actually turned out to be. Those who know me will already know that I like compact and well engineered products
The Blackbody head came with its expensive umbilical cable but not the temperature controller. If it used the usual EOI 19" rack mount temperature controller, I would not have wanted it anyway. I will need to build a nice compact PID based controller to match the diminutive dimensions of the head unit. To do this I need to better understand the EOI Blackbody design so it was time to remove the cover
Once the cover had been removed, the very neat engineering within was revealed
This unit is a beautifully scaled down version of the other two (full size) Cavity Blackbodies that I own. There is the Cavity 'core' module that contains the metal cavity tube, helical heater, temperature sensor(s) and lots of high temperature ceramic wadding insulation. That 'core' module is solidly mounted on a pair of yokes that are, in turn, mounted on the thick aluminium base plate. The front and rear panels are made from the same thick aluminium plate so this unit is nice and solid. These units are made in relatively small numbers and are hand made rather than the product of a mass production automated assembly line. They are very expensive as a result.
My investigations into the technology within the head unit revealed that it contains a single heater of 10 Ohms resistance, a PT100 RTD and a Thermocouple. Why an RTD and Thermocouple ? Well the RTD is the sensor for the temperature controller feedback loop whilst the Thermocouple is used with a cold junction reference for either calibration of the temperature controller, or monitoring of the cavity temperature using an accurate meter. On high temperature cavity Blackbodies it is common to find an 'S' type Thermocouple in this role.
This unit will be very convenient due to its portability and I will make up a Tripod mount to fit to the base plate to increase its mounting versatility. There are already tapped screw holes in the base for just such an adaption.
Well enough from me on this dinky little unit.... to the pictures......
In the pictures you will see Bailey and Oskar examining the new arrival and a CD case is used for scale to show just how compact this cavity Blackbody is
Fraser