Cheap panel mountable frequency counter

[guitarfool]

Oh, this is fun

It all depends on how you define "frequency". In electronics, the analogy of a rotating object is usually used to describe an oscillation, in which case you are talking about a rotational rate. Or you can think of oscillation in terms of a reciprocating object. In the first case, the rate can be positive or negative depending on the direction of rotation. In the second case it can only be positive.

In physics, "frequency" is the inverse of the TIME PERIOD. This is a scalar quantity, and will be positive unless you want to make time go backwards.

However, PHASE ANGLE can be increasing or decreasing, so I guess if "frequency" means rate of change of phase angle, then yes, it can have a direction. But in this case you're defining "frequency" to be in terms of angle per unit time. This is much like the difference between "speed" and "velocity", except we're using the same word for both

In a through-zero oscillator, it's really just a case of reversing the waveform when the linear control voltage goes negative. It's the PHASE ANGLE (and not time) that's going backwards.

I think HP called it a frequency COUNTER rather than a frequency METER for this reason. You're counting the zero crossings of the signal anyway. Whether you count the rising edges or the falling edges of the signal isn't going to make a whole lot of difference.

<SILLY>
But just to be safe, I think I'll build mine with an inverting amp that can be switched in and out. That way I can switch it out to measure positive frequencies (count the rising edges), or switch it in to measure negative frequencies (the falling edges)

OTOH, if a negative frequency oscillator is really going backwards in time, wouldn't such an oscillator STOP working once you built it and powered it up? I think I may have a couple of those
</SILLY>

[factus10]

[urbanscallywag]

Nice post guitarfool. Phasors, yet another piece in the complex signal puzzle!

[guitarfool]

[yusynth]

[guitarfool]

Okay, I got mine in the mail Friday and have one mounted on a temporary panel in my modular. It went together easily and seems to work quite well with synth level signals.

However, after disconnecting the display from the other PCB to mount it to the panel, I carelessly misaligned the 2 when reconnecting (off by one pin). No magic smoke came out, but there was a very foul odor after which the display no longer worked I figure Vss was unconnected and Vdd saw 5 volts. Fortunately I bought 2 of these, so I had a spare. And Nuxie1 sells the display separately

[jksuperstar]

Can this also display the note associated with the frequency? Seems like it has the processor, it should be fairly trivial to have a function much like a chromatic tuner has (displaying the nearest Note, sharp or flat in cents maybe?)

Just an idea.

[guitarfool]