"Models 5211A and 5211B have a maximum counting rate of 300 kc and make direct frequency and ratio measurements. They also measure speed in rpm and rps when used with transducers and count events occuring within a selected period of time. Both offer manual control of the gate by frontpanel function switch, by external contact closure or by 3 volts peak positive pulses at least 10 usec wide at half-amplitude points." (hp, Catalog, 1965)

BRIEF SPECS

This universal counter is not very exciting, except for its nice display. To fit the 'columnar' readout in narrow cabinets, hp used two columns of numbers per readout. This means that the displayed count is even funnier to read from up-down and with different space intervals between the numbers. The decimal-counting-units (5212A-4B) are similar to the ones used in the hp 3440A digital voltmeter except for the readout. The mainframe itself has just wiring and some few componets - most of the circuitry is placed on plug-in-boards. By the way - hp did manufacture most of its transformers by themself. PAECO (Palo Alto Engineering Company) was the associated subsidary. As two of the DCU's are not working properly, I made an extender board to raise the plug-in's while the instrument is operating. Hopefully there is no fault within the photoconductor plate which controls the neon bulbs. If someone has some spare DCU's please let me know!