[time-nuts] J06 HP-59992A time interval calibrator for HP-531xx counters

Mark Sims holrum at hotmail.com
Sat Jul 8 09:31:29 EDT 2017

To do a full and proper calibration of the HP-53131/53132/53181 counters you need a J06 HP-59992A time interval calibrator... lots of luck finding one of those.   Looking at the manual, it is actually a fairly simple device which can be greatly simplified for the task of calibrating a 531XX counter.

The main task is to generate 10 MHz square waves with 50% duty cycle.  Four versions of the signal are generated (two positive and two with inverted phase).  One of four combos of these signals (P1-P2,  P2-P1,  N1-N2, and N2-N1) are driven to two output connectors.   The 59992A uses splitters and phase shifters to generate the signals and can handle analog signals.  The 531xx cal uses square waves so those signals can be generated digitally.   

My first idea is to take a 20 MHz oscillator and divide it by two to get a 50% duty cycle. One could also do something like squaring a 10 MHz osc with something like the Wenzel squarer... that would provide a more stable signal frequency wise but that might add some asymmetries to the signal.  Feeding the 10 Mhz osc through a doubler and dividing the squared signal might provide the best solution.

The 531xx cal procedure uses a +/- 0.50V signal.   I need a simple and cheap circuit to level shift the TTL signal to +/- 0.50V  It probably needs clean, stable, fast edges and able to drive a 50 ohm load (the manuals don't specify the required edge rates and load).   Any ideas for a suitable level shifter / buffer?  It would also be super nice if it could work from a single supply...

Also,  if such a cal board was laid out would there be any interest in making it available for others to build?  

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