HP 5328A universal frequency counter teardown
Kenneth scored two HP universal frequency counters and popped them open. One generates the timebase from an uncompensated oscillator in a TO-5 package, while the other uses a large temperature controlled oven oscillator:
This entry was posted in Teardowns and tagged HP, teardown, universal counter.
here is both of my counters measuring the same 1pps taken from my AdaFruit GPS receiver. The lower one with the oven-compensated oscillator (which is marked as being calibrated in 1999) is spot on, while the top counter using an unprotected crystal oscillator drifts up and down 0.1-0.2ppm, and is almost 5ppm slow…The standard time base is rated for 2.5ppm drift between 0 and 50 degrees Celsius, where the [oven oscillator] time base has the much tighter 0.007ppm. Since these counters display eight (or nine) digits, 2.5ppm is very visible, where 0.007ppm will at worst only effect the least significant digit.