Cycling computer for Dutch bike

[yoyo]

Mr Yoyo finally got round to putting my computer from my old bike onto my Batavus Alamo. It is wireless and he recalibrated it etc. However, it is only working temperamentally and is not measuring distance accurately; speed is being recorded at times but mostly I am doing 0mph!! Are my high handlebars too far from the sensor on the wheel? Has anyone any suggestions? Thank you.

 

[Andy in Sig]

I think the best start place would be the manufacturer's website as the tech spec might include the max magnet-sensor distance. Perhaps if you posted the name of maker and model here, somebody might have the relevant knowledge.