bont trip 3 cadence sensor

Sprool

Having some problems getting the cadence sensor and magnet set up with a bontrager trip 3. In order to register cadence I have to have the magnet passing about 1mm from the sensor, really just grazing the plastic casing, else I get zero reading. Most of the time the cadence reading is ok but every few revs it reads ½, like it miscounts every 4th or 5th revolution. Its driving me nuts as I know it should not do this. I searched internet and pdf instructions but can't find anything about the correct alignment of magnet against sensor. Any advice welcome - positioning, stronger magnet?

sungod

if the problem is due to weak magnet/insensitive sensor...

get a pack of rare earth magnets on ebay, umpteen sizes available, there're usually offers of 10+ for a couple of quid

you can glue or tape one to the crank, or if position and material allow simply attach one to the end of the pedal axle where it pokes through the crank