SPM jumpy on PM2

[der_andere_Ruderer]

Hello Forum,

I have aquired a used Model C Rower with a PM2, enhanced model (so it says on the inside). It seems to work ok, sometimes the meters go a bit faster than usual but I'm ok with that. However, the smp value is all over the board, jumpy and goes from -- to 40 to 88 to 65 to 22 and so on. Totally irregular and certainly not my rowing skills.

Last week I took off the flywheel to check the magnets and they seem ok, cleaned the sensor and the magnets but it seems the sensor is for measuring distance? Is there another sensor for spm that is placed somewhere else?

The PM2 looks clean, no battery leftovers to be seen.

Thank you

[Citroen]

Only one sensor and three magnets on a model C.
viewtopic.php?p=489874#p489874

Strokes per minute are seen by the rising edge of the tacho signal.

[Nomath]

There is only one sensor. It measures the flywheel speed. Because the relation between flywheel speed and chain speed during the main drive is fixed, the sensor is also able to measure the displacement (=distance) of the handlebar from the point where handlebar speed caught up with the flywheel speed to the point where the handle speed drops below the flywheel speed. The real handle displacement in a drive is longer.
The sensor is also able to measure handle force, for the same reason.

[Carl Watts]

The PM2 is pretty good in that in general it either works or it doesn't in this area.

Are you sure all 3 of the magnets are good ? it only takes one to be a problem and it will not work. If there is evidence of lots of rust on the rower, a magnet could be a problem.

Its also possibly that battery leakage has affected the circuit which is at the top left of the battery compartment. Usually any leakage goes down the board into the power supply area but if the rower was stored on its nose in the upright position the leakage goes the other way.

There are 6 screws in the back that are easily removed, any signs of corrosion and thats the problem.

[jamesg]

Totally irregular and certainly not my rowing skills.

Don't worry, just keep your erg stroke long and strong and pull plenty of them, as if afloat. Sweat will tell, and you can always use a chest belt if really desperate for numbers.

[der_andere_Ruderer]

ok, I'll further investigate the Monitor then and see if there's any corrosion. There is no rust and it seems in pretty good condition overall. I'm also not too concerned about the SPM but this stuff triggers the tinkerer in me.