Triumph Rat Motorcycle Forums banner
1 - 3 of 3 Posts

· Super Moderator
Joined
·
21,920 Posts
It is indeed a digital type signal that pulses as the wheel revolves - these are always hall effect /inductively coupled and generate an emf (voltage) that is induced by the electrical field changing due to a magnet or metal object passing through the field.
Now these devices all have three wires - power, ground & the O/P which is the one that pulses. You can typically replace any sensor with one from another vendor as the electronics in the speedo has a buffer that normalizes the voltage required for the circuitry.
The trick to matching is not so much in the magnitude of the voltage of the pulse that is generated, but in equating how many pulses per revolution there are between OEM & the aftermarket device utilized.
Now most after-market speedo's all have built-in calibration circuits so you can accommodate different number of input pulses per rev but the OEM gauge is fixed, so it's important to know how many pulses are generated in a single revolution of the front wheel by the OEM sensor
Also recognize that if you install a sensor on the rear wheel drive, it will be a different calibration because one revolution of the back wheel is different distance to one of the front, due to the different tire sizes. However you can install one of the after-market calibration devices to accommodate that fairly small difference (however they won't accomodate a substantial difference in number of pulses, like 2x or greater, more like maybe 50% max)

If indeed the OEM front wheel sensor is 4 per rev, (I don't absolutely know this for sure) then you can use any number of available after-market sensors on the rear wheel and utilize 4 trigger magnets then add the cal device (like Speedohealer or YellowBox) to fine tune it.

The key question is if the OEM is really 4 pulses per rev!
Is there any way to tell from looking inside the device?
Ideally you stick an o'scope of the O/put & just see how many pulses you detect in a revolution of the wheel. I'm not sure if you'll be able to see it with just a digital meter but you could try.

If I could temporarily get hold of a digital speedo or OEMsender, I be happy to test it out for the greater good.
 

· Super Moderator
Joined
·
21,920 Posts
There are quite a few commercial options available that come as a kit with wiring, connectors etc
For example, you can use the Acumen one I used with mounting details in this thread - Procycle Digital Speedometer Retrofit

That was the drive for the Acumen Digital Gear indicator which is actually available separately. I actually used the single sender to drive both the gear indicator & the speedo together. Other options would be the Veypor drive kit (only comes with one magnet but easy enough to add more) or options from Dakota digital if you care to do a search on those.
It sounds like you should be safe enough in using one of these per the info from Stlakid and then just playing with the number of sensor magnets (either 2 or 4) to see what gives close to calibration. Then add one of these Yellow box calibration devices in-line to fine trim it for determoned accuracy.
YellowBox

[ This message was edited by: DEcosse on 2006-12-09 13:52 ]
 

· Super Moderator
Joined
·
21,920 Posts
On 2006-12-09 21:04, buggyto wrote:
.... For the calibration I plan to put the target on a disc with a slot and move the sensor up or down ....
:???:

Not sure if I'm mis-understanding you or you're mis-understanding how it works:
The effective diameter of the sensor/trigger is inconsequential - it will give 'x' number of counts per wheel rotation depending on how many trigger magnets you use - doesn't matter where they are located on the wheel or any part of the rotating assembly. The effect of the wheel diameter however will affect the net calibration on the speedo itself. You cannot compensate for this difference by moving the sensor/trigger - the number of counts per revolution will remain the same. That's why you use the Yellowbox, to give you a % change that is not achived by a whole number count of trigger magnets (i.e. - if you used 4 magnets & were 20% slow, you would add one more magnet & be correct; however if you were something like 8% or 13% or 24% fast or slow, only way to compensate is to have the yellowbox adjust for it.)


[ This message was edited by: DEcosse on 2006-12-10 00:46 ]
 
1 - 3 of 3 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top