Because You Asked For It! This saga took place over several months.
I post the schematic(s). If you want more (pcb layout, sw, etc), I will make them available but be aware that the file formats may not be what you can use and some significant re-working on your part might be needed.
What a struggle holy shit. Going from pic to atmel at the last instant, and throwing away all that fancy work in getting the pic to work in its constrained place.. prescalers, shift registers… damn.
I have seen things like this that when they get close to the end of a measurement range, will switch in or out another decade of L/C to improve measurement accuracy, but that would require more space and another few relays, and of course, all the calibration required for it.
As for measuring frequency i would use a schmidt trigger to give you your square wave to measure. As the measurement time drops, use the relay to switch out/in components to once again reduce the oscillator frequency. The reason accuracy drops is that as the frequency gets higher and higher the period timer is getting closer and closer to the timer counter period.
Basically a form of nyquist frequency issue. The bigger the ratio between the counter timer and the period you are measuring, the more accurate the measurement is (but the slower it takes as well)
Because You Asked For It! This saga took place over several months.
I post the schematic(s). If you want more (pcb layout, sw, etc), I will make them available but be aware that the file formats may not be what you can use and some significant re-working on your part might be needed.
Windows 98 ++
Wow, you’ve got determination. That was a lot of effort!
What a struggle holy shit. Going from pic to atmel at the last instant, and throwing away all that fancy work in getting the pic to work in its constrained place.. prescalers, shift registers… damn.
I have seen things like this that when they get close to the end of a measurement range, will switch in or out another decade of L/C to improve measurement accuracy, but that would require more space and another few relays, and of course, all the calibration required for it.
As for measuring frequency i would use a schmidt trigger to give you your square wave to measure. As the measurement time drops, use the relay to switch out/in components to once again reduce the oscillator frequency. The reason accuracy drops is that as the frequency gets higher and higher the period timer is getting closer and closer to the timer counter period.
Basically a form of nyquist frequency issue. The bigger the ratio between the counter timer and the period you are measuring, the more accurate the measurement is (but the slower it takes as well)