Electronics > Projects, Designs, and Technical Stuff
Concept 2 rowing machine sensor puzzle
jpb:
Here is a puzzle.
I have an old (2003) Concept II rowing machine (or ergo) and a week ago the Performance Monitor failed to register any output (stayed on zero).
The sensor system (as I've found out in the process of fixing it) consists of three small magnets in the fly wheel and a sensor which is just a coil of wire around a metal pin (see attached pictures).
My sensor produced no output but noise when I attached a scope. The magnets on the fly wheel were ok (not rusted and could hold a paper-clip).
I've replaced the sensor today with a new sensor which now works nicely and produces output as shown in the pictures.
My puzzle though is that the impedance of the broken sensor is nearly the same as the new sensor (110 ohms instead of 109 ohms) - that is the wire hasn't gone open circuit which is what commonly happens (according to forums I've looked on).
So how can the coil have broken without changing impedance?
(Apologies for the rather out-of-focus scope shots - I had to shut the garage door to get rid of reflections and then it was a little dark.)
maginnovision:
The resistance you're reading is probably a resistor, not a coil. Just look up variable reluctance sensors. My model E uses a different type of sensor so I couldn't tell you exactly how your is made but you could open it up yourself.
mikerj:
A shorted turn or two could have negligible impact on the measured resistance, but would significantly reduce the output of the sensor.
ace1903:
Maybe there is a bad solder connection or intermittent contact. I had similar issues with other sensors.
When you disassemble the sensor cable has bent in different directions and connection is reestablished.
Try to take measurements while bending the cable and tapping on the coil with some plastic hammer.
mjkuwp:
--- Quote from: ace1903 on July 19, 2020, 06:54:11 am ---Maybe there is a bad solder connection or intermittent contact. I had similar issues with other sensors.
When you disassemble the sensor cable has bent in different directions and connection is reestablished.
Try to take measurements while bending the cable and tapping on the coil with some plastic hammer.
--- End quote ---
I think it is this ^^
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