Speedometer

I got a new speedo. I probably sound silly. But do you need to put the magnet and sensor in a specific measurement on the spoke and fork.
Really how does it know when you put the wheel measurement in the settings.
If you put it lower or higher on the spokes wouldn’t it read different with the same measurement in the setting.

(Warning: this is going to get more in-depth the more you read.)

It measures revolutions per second and then multiplies that by the diameter (distance traveled per revolution) you entered by wheel size.

Placing it higher or lower on the spokes does not affect rpms.

The magnet needs to pass close enough to the sensor so that it can feel the magnetic blip as it passes by. A couple millimeters gap should be OK.

I’d put it in the middle or where ever works.

Closer to the rim, the computer would see a shorter but more intense pulse as the magnet passes by. This is because the voltage generated is the result of the rate of change in the magnetic field around the pickup coil. (The rim is traveling faster than the hub but at the same revolutions per second because the rim has a longer circle to travel in the same time period)

Conversely, a slowly turning wheel with the sensor mounted close to the hub would produce a weak and spread out pulse which may not get detected at all.

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Awesome. Thank you for that. It had me mind boggeled. Makes sence now lol.

Generally the hardware that came with the computer determines where it goes. Because it only reaches or adjusts so much. The distance between the spokes and fork are less near the hub and more near the rim. The old ones I’ve used usually go in the middle or a bit lower.

I put mine in the middle. Cause it didn’t specify where to put it.

Don’t some sensors use reed switches activated by the permanent magnet? How would that affect the analysis? :microscope:

I would say that you should put the magnet close to the hub, less rotational inertia so you will accelerate much faster!!!1 :laughing:

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I would be surprised to see a reed switch used. Possible, I suppose. They are good for slow moving applications like door sensors etc… but I’m not sure if you would get a good closure at higher speeds.

I put it up to the gps. It’s very accurate. And the gps is dead on with the car speedo. No complaints. :grinning:

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