I recently saw an IR Industries model 463 Cavity type Blackbody for sale in the USA at a very attractive price. Further investigation of the sellers other items discovered the matching IR Systems IR101B temperature controller at an amazing price. I worked out the import and shipping cost and the purchase made sense so I bought both units.
The package arrived today and survived its long journey thanks to great packing by the seller.
I understand that his is an estate sale item and the seller knew little about what it was and had not paired the controller with the Blackbody as a result.
As those who know about Blackbodies will tell you..... they are specialist items made by only a few companies (though Corona Virus had changed this a bit) and so they are generally very expensive. A high temperature Blackbody like the IR industries 463 is a relatively simple Physical construction but making your own is neither cheap nor easy and the cavity needs to be decent if good performance is to be expected of it. Cavity Blackbodies are capable of emissivity close to 1.0 and .99 is common. This combined with a temperature range of 50C to 1050C can make such a Blackbody very useful when testing and repairing thermal imaging and IR measurement systems. They are are also useful for experimentation where a decent high temperature source is required. The 463 is a very well designed and built cavity Blackbody and, even though the design dates back to the 1970’s, or even earlier, it remains valid as it is basically a precision cavity, with high emissivity coating, inside a heating element and surrounded by insulation. The temperature sensors used in high temperature Blackbodies are commonly Thermocouples as RTD’s tend to operate below 500C. Some Blackbodies use specialist RTD’s that are capable of higher temperatures however. Type S high temperature thermocouples are a common sensor used in many high temperature cavity Blackbodies.
So the Cavity Blackbody design can be old, yet still valid today........ what about the temperature controller ? Well that IS an area where technology has improved greatly since the 1970’s ! It will come as no surprise that the design of the temperature controllers has migrated from analogue controllers to digital types that are PID based. The modern controllers are usually a good quality PID design with thermocouple or RTD sensor input and SSR output that is driven by a PWM signal. Such modern controllers are more user friendly and accurate than the older dial type analogue controllers, such as that provided with the 463.
The Controller for a Blackbody need not be that difficult to construct these days thanks to the ready made and easily configures PID temperature controllers from the likes of Eurotherm. They offer all manner of configuration options and are not too expensive if a used unit is procured. So what about the analogue controller that came with my 463 ? Well it cost me around $10 and was worth every penny for the special multi pole connector alone. Such connectors can be eye-wateringly expensive. I intend to test the IR Industries Blackbody with its original IR101B analogue controller but may make a more modern controller for it in due course. I already have plenty of suitable PID temperature controllers. If the IR101B controller is still stable and reasonably accurate, I can use it as I will measure the cavity temperature with a precision Minolta IR thermometer that I have.
I had zero time to play with the unit today but did take the lid off of the controller to see what lurked inside. Well I discovered a single SN72741 (741) Op-Amp hiding in there and lots of discrete passive components and transistors. The data code on the 741 Op-Amp is 1976 ! This is an old model, but the analogue controller suggested that so no surprises. Provided the Cavity Blackbody heater is still OK, the age of it is of little concern. The unit likely uses ceramic insulation rather than Asbestos wadding but I will not be taking it apart any time soon.
The controller design may provide a giggle for younger readers so I provide some pictures for your entertainment. There are some precision resistors used in the design but it is all very ‘old school’ from the design of the PCB through to the components used.
More on this little restoration project as and when I get some work done on it.
The external pictures are rubbish as I grabbed them from the auction using my iPad. Better will follow in due course.
Fraser
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