SPM errors on a Model C / PM2+

mtgreaves · Post by **mtgreaves** » January 16th, 2007, 7:57 pm

While I am erging, occasionally the SPM readout on my Model C / PM2+ will display a nonsense number (between 70 and 80) for a single stroke, and then settle back to my normal 26 SPM. There seems to be no particular pattern to this; it happens whether I am pulling hard or easy, and sometimes I will notice 2 or 3 bad readings over 15 strokes, and other times I won't notice it over an entire 30 minute piece. Most days it happens once or twice in a 30 minute piece.

I have checked the leads going to the fan speed sensor and they look OK. The sensor itself is clean. The erg is about 7 years old and going strong otherwise.

Two questions:

1. Is there something else I can check?
2. Is this affecting the time/distance computations on the PM2+?

Thanks,
Mark

PaulS · Post by **PaulS** » January 16th, 2007, 9:22 pm

1) Fresh Batteries, and if you move the monitor arm regularly it's possible that the wire inside the sensor cable has broken and you are seeing the product of that unstable connection. I see this on our club ergs from time to time.

2) Unless you are seeing a similar jump in the Pace reading it is probably not effecting the overall avg pace and distance readings. If it is a problem with the sensor wire it will not heal itself.

I would suggest giving C2 a call when you have a few minutes to go through some diagnostic tests while on the phone, they will likely be able to narrow down what you need quickly. A replacement sensor is not very expensive and will last another 7+ years.

It's also possible that the PM2 is finally giving up the ghost, but that's more of a long shot.

mtgreaves · Post by **mtgreaves** » January 17th, 2007, 2:14 am

Thanks for the advice, Paul.

1. I should have mentioned that the PM2+ batteries are fresh.

2. The monitor arm gets moved about once a month when my kindergartener decides to try and mimic daddy on the erg. Her form needs work, but she's got a lot of enthusiasm! If the SPM fault is caused by an intermittent short in that wire it will be tough to track down.

I'll give C2 a call, and if there is an interesting resolution to this I'll post it back to the forum. Anyone else have a similar SPM problem?

Thanks,
Mark

c2scott · Post by **c2scott** » January 18th, 2007, 6:36 pm

Yes, give Concept2 a call; Shawn might be your best bet. Also, think about your stroke. I'm not placing blame here, but I've seen some folks that have a wierd technique which results in the chain going slack in the middle of the stroke resulting in the monitor seeing a de-acceleration, which ends the stroke, then a 2nd stroke right after; this results in a high stroke rate... Also, check the distance between the sensor and the flywheel, make sure it's in position; and check the magnets are all in place on your C flywheel.

mtgreaves · Post by **mtgreaves** » January 29th, 2007, 2:34 pm

Yes, give Concept2 a call; Shawn might be your best bet. Also, think about your stroke. I'm not placing blame here, but I've seen some folks that have a wierd technique which results in the chain going slack in the middle of the stroke resulting in the monitor seeing a de-acceleration, which ends the stroke, then a 2nd stroke right after; this results in a high stroke rate... Also, check the distance between the sensor and the flywheel, make sure it's in position; and check the magnets are all in place on your C flywheel.

While my stroke could definitely use some refinement, the SPM problem still occurs when I concentrate on pulling exceptionally smoothly.

I spoke to Shawn, and he recommended pulling the flywheel and checking that the magnets were properly seated and positioned, and that they were clean. He also confirmed that if the sensor missed one of the magents as it was rotating by, the PM2 would interpret the longer inter-magnet time as a deceleration, which would end the stroke early. This would account for the high instantaneous SPM readings.