The most straightforward method these days would be a small microcontroller implementing a pulse width modulation digital to analog converter.
The analog route is pretty easy though. A traditional charge or current pump can operate down to 30 Hz but will have an output ripple versus settling time trade off. That can be solved with a sample and hold. Charge balancing frequency to voltage converter on page 11: http://cds.linear.com/docs/en/application-note/an03f.pdf Current pump frequency to voltage converter with sample and hold inside the feedback loop on page 4: http://www.ti.com/lit/an/sbva005/sbva005.pdf Given the low frequencies involved, a resetable ramp generator with sample and hold would work great. The fixed reset time would be so short compared to the minimum input period that accuracy would not significantly suffer. On Tue, 19 Feb 2013 16:58:04 -0800 (PST), Paul Cianciolo <[email protected]> wrote: >Hello Folks, > >I am working on a project intended to convert an analog ECG signal to a >voltage proportional the heart rate, >The actual electrodes instrumentation amp is pretty much working fine so no >worries there. > >The problem is, and here is where the relationship to time nut comes in. >The signal output from the instrumentation amplifiers will be at a rate of >approx 60 BPM or pulses, up to perhaps 90 BPM. > >The purpose of this apparatus is to print a rolling chart on the screen of a >computer of heart BPM and then try different technicues of meditaion and >calming technicues to lower my heart rate for short periods of time. > >My first tthought was a frequency to voltage IC like the LM2907 or the 2917 >but I get the impresiion from the data sheets that these chips will not work >at these very low 1 Hz applications, > >Then I thought maybe one of the frequecy counters could be configured as a >rate meter and output a proportional voltage I need. >No luck here either. >Te latter components seem tobe somewhat time relatedand that is why I posted >here.\\ > >Thank you for reading this and for any suggestions you folks might offer. > >PaulC >W1VLF _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
