Recore 3D printing board developer [Elias Bakken] have Release of automatic test procedures He used a stack of four (at least) old HP test equipment for development. In addition, his test fixtures and test concepts are also very interesting.
In addition to making the nail bed test fixture, he also designed a relay multiplexing board that can select one of 23 different voltages for measurement. We like the mechanical latching relay he chose in this application-it not only saves power, but also does not subject the test board to any magnetic field (except when switching states).
exist [Elias]The unit under test (UUT) actually arranges the test process by itself. This is not as crazy as it sounds. The processor is highly integrated in a package, plus external DRAM. If the CPU is fully booted and passes a simple self-check procedure, there is no reason not to use the onboard processor as the main test control computer. If your processor is very small and resources and connections are limited, this may be a problematic decision. But in the case of Recore, the processor is a quad-core ARM A53 SoC running Debian Linux-this arrangement itself can be used as an automatic test computer in other projects.
In the video below, [Elias] Guide us to complete the basic test, and then focus on the core of the Recore board test: calibrating the input signal conditioning circuit. Instead of using very expensive precision resistors, [Elias] Choose a more economical 1% resistor for the preamplifier circuit. The trade-off here is the need to calibrate each channel, possibly at multiple temperature points. In this case, the use of test fixtures, automated test scripts, and programmable test equipment stacks really work.
[Elias] Still thinking about some of the problems he found when calibrating the thermocouple, so his adventure is not completely over. If you want to know what Recore is, check out this June article. Have you ever used a microprocessor on a circuit board for self-testing, whether it was a stand-alone test or in combination with an external fixture? Please let us know in the comments below.