need to sharpen those tools !

In the process of working on the 555 metronome I was using my B&K 2190d digital scope.

B&K 2190d

  It has a lot of nice features including measuring the period of a waveform.  But it only does this to a precision of 10 milliseconds for a long period waveform (over a second in this case).

I got out a frequency counter that I had purchased on ebay, but it doesn't measure waveform period.  I do have an HP 5328 counter but unfortunately it needs fixing.

Then I recalled a Morse Speedometer project I had (see http://wb9kzy.com/projects.htm ).  I got it out thinking that it would "display" the period in Morse code.  But it didn't work.  So I dug into the code and got it to read half the period.  The resolution is 100 us.

The 555 timer outputs a 15 ms wide blip up to 9 volts and then goes low for the rest of the period.  

For 40 beats per minute the period is 60 seconds/40 beats or 1.5 seconds/beat so 15 ms high, then 1485 ms low for 1500 ms total.   For 50 beats per minute: 60/50 = 1.2 seconds so 15 ms high then 1185 ms low.

I'll give it another try tomorrow and hopefully full period measurement plus add an LCD display, even though Morse code output is fine, it's handier when calibrating a pot to be able to see the digits change every 1.5 seconds rather than having to wait for 5 Morse digits to be sent.

Another idea would be to convert the period measurement into a beats per minute display, we'll see.

Best Regards,
Chuck, WB9KZY
http://wb9kzy.com/ham.htm