Bike Forums - View Single Post - Which Power Meter?
View Single Post
Old 10-23-19, 05:57 AM
Blast from the Past
Voodoo76's Avatar
Join Date: Mar 2005
Location: Schertz TX
Posts: 3,138

Bikes: Ridley Excal, CAAD10, CAAD12, Felt DA, Dolan

Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 183 Post(s)
Liked 28 Times in 24 Posts
Originally Posted by carleton View Post
Cadence is needed to calculate Power. If Cadence is late, Power will be, too.

The Wired SRM PC5 was great for standing starts because it could be equipped with TWO reed switches. Meaning it got cadence readings every HALF pedal stroke. You need 2 readings to calculate the time between readings (rate). Using a PC5, you could get 2 readings in 1 rotation of the crank...thus making Cadence available for the Power calculation faster than any other system...twice as fast as even a PC5 system with a single reed switch.

SRM stopped putting 2 reed switches on their SRMs back in like 2011 or 2012. They also removed that "Two Reed Switch" option in their software.
The earlier road Quarqs, ones that required a magnet, had multiple switches (as I recall 4). They primarily used that to verify direction of crank rotation, you could zero the meter by pedaling backwards.

This is a potential advantage for wheel based systems like Power tap. Update frequency for wheel rotation speed as the "v" in the power equation is 3 to 3.5 times the crank "v" for typical gearing.
Voodoo76 is offline