Adu's Electronic Lab For Hobby

I got some low cost VFDs, and also get a paperbox after my phone repaired by the Apple's service. I want to use them to build something, maybe a clock, or a thermometer, but due to VFD need high current power consuption, I decide to use them to build a voltage meter.   After open the holes on the paper box, it's better to use Cyanoacrylate glue to make the edge harder and robuster.   Here is the pictures for inside:  And here is the final view: I only prepared 2 buttons for it, left used to change the measurement speed(ODR), from 2.5Hz to 50 Hz, right side used for self calibration. And the measurement range is +-4.7V, input impedance is greater than 15Mohm. Then i want to check it's accuracy, I need a calibrator, thus I found an old Fluke 343A on Ebay Kleinanzeign,  after paied the seller 400Euro the seller disappers, he is a cheater, I never imaged a cheater will sell such rare things, build in 1980s. I thought normally they will sell iphone, computers 💔 Then I need to f