[sdiy] Re: S[DIY} frequency counter

[Magnus Danielson]

David G. Dixon wrote:
>> <snip...>
>  
>> All these types can have improved by using interpolator curcuits that
>> improve the time-resolution at the start and stop of the gating period.
>> A virtually higher reference oscillator is produced. For instance, in
>> the HP 5335A the analog interpolators provide 200 time improved gain, so
>> the 10 MHz time base oscillator achieves 1 ns of resolution (you have a
>> +/- 1 cycle problem which removes some of the resolution).
> 
> Hey, Magnus, you wouldn't happen to have a schematic for a good counter
> circuit, would you?
> 

Several. You can get the Operations & Service manuals for the HP 5335A 
and HP 5370A/B from Agilents manual site. The HP 5335A is closer to 
normal life, but I have both and even better counters that outgears them 
by far.

The basic principles is however very simple and you should be able to 
come up with something without going into excesses. Checkout the HP 
Application Note 200 series. Good reading. Apply knoweldge about modern 
devices and you will probably come up with a good price performance 
match than cloning any of the above gear, as they depend on alot of 
chips of which some is special made unobtainium.

The MRC chip of the HP5335A is maybe best described in the HP5334A 
manual but in general it is just a couple of counters on a chip and some 
added logic. CPLD-level of design.

Cheers,
Magnus