AW: reciprocal frequency counter

[Martin Czech]

> 	>Sometimes it would be nice to have a DVM and a frequency counter
> 	>as a module for a modular system. E.g for tuning and trimming
> procedures
> 	>as well as for practical work.
> 	>
> 	>DVM is no problem, there are 5 digit kits available. 
> 	>
> 	>Most frequency counters suffer from the fact that they need very
> 	>long gate times for audio frequencys, ie. much latency. Of course,
> 	>one could measure the period instead, but say in 2 seconds how many
> 	>Hertz are 1/0.003674 s ?  (A very "clever" person suggested using a
> pll,
> 	>to make the frequency higher ...) Therefore reciporcal counters
> exist,
> 	>with a microcomputer inside that does this operation for the user,
> so
> 	>you really measure period, but get a frequency reading. Up to now,
> you
> 	>could buy these things for $500 or so at RS etc., now I've found a
> kit to
> 	>do your own for a modest price at ELV Electronics,
> (http://www.elv.de),
> 	>a german company that does kits and complete devices. I found it in
> their
> 	>free catalogue, not on the web.
> 
> DVM: My Multimeter is terribly slow, probably because of the cheap
> dual slope ADC. Are there cheap Panel Meters that convert faster?
> 
In the region of 140 DM there are 4.5 digit types with up to 2 samples per second.
Just looked into the RS catalogue.

> Anybody found an O'Scope small enough (and unexpensive) to fit
> into a Modular ?
> 
I also thought about this. There are cheap Chinese or Korean things
(1MHz bandwqidth) at Conrad or Voelkner Electronic in Germany.  ELV has
developped an scope kit together with Hameg. Maybe you should order the
elv katalog on their web site. It's free !

OTOH : What kind of interference will come from the scope?
I mean horizontal deflection e.g.

m.c.