Since the 1970s the voltage reference inside the highest precision commercial voltmeters has been a zener diode. For example, the current “champion”, the HP/Agilent3548A is based on an LTZ1000.

Okay, I'm building a serial link cable for my TI calculator and the plans call for two zener diodes. What exactly is a zener diode? Is that just a regular diode, because I have some diodes, and if ...