Repetition frequency is just that - regardless of the er, frequency.
Beats per Minute, Breaths per Minute ... or Full Moons per Lunar Month ... it's still a regular pattern that can be measured. Remember, though, that Hertz is taken to mean "cycles per second" (so recording phases of the moon in Hertz would not really be appropriate)! So you're right, it's best kept for frequencies above 1 per second.
Notice here though that, in the Grand Scheme of things, we're talking about very low frequencies.
Even ELF (Extremely Low Frequency) is in the range 30 to 300 Hz.
@Sean: if repetitive pulses can be displayed, then the period can be measured.
BPM to Hertz? The reciprocal of the period (
eg, R-wave peak to R-wave peak in a normal ECG waveform).
30 BPM : period is 2 seconds : 1/2 = 0.5 Hz
60 BPM : period is 1 second : 1/1 = 1.0 Hz
120 BPM : period is 0.5 second : 1/0.5 = 2.0 Hz
180 BPM : period is 0.33. second : 1/0.33. = 3.0 Hz (approx)
240 BPM : period is 0.25 second : 1/0.25 = 4.0 Hz
Whilst we're at it, here are a few more (some of which can be argued about, I'm sure):-
50 Hz mains (20 ms)
60 Hz mains (16.66 ms)
"Shortwave Diathermy" (Electrosurgery):-
- 1.8 MHz (0.555 µs or 555 ns)
Shortwave Therapy:-
- 27.12 MHz (0.0369 µs or 36.9 ns)
TENS units:-
- 15-175 Hz typical
- typical pulse width 50-200 µs
And here's a final question for you all:- if a 60 BPM ECG is considered to be a 1 Hertz signal (and I'm not agreeing to that, by the way) - then what is its wavelength?
