Positive or negative RPM signal

[Marbro_za]

Hey guys
Im looking at buying a speedometer for my bike, I would love a factory one, but thats not in the price range.

So the ones i have been looking at mention i need to tell them if i have a positive or negative RPM signal, How the feck do i find that out?
Its for a 2004 Yamaha FZ6 ,

Help please

 

[Shirou]

You should ask them what the flick do they mean by that.
There are no negative signals on a motorcycle. The speed sensor readout is a positive pulse. Maybe they're referring to the signal width or duty cycle or the best bet will be if the sensor outputs a high pulse when idle and goes low when it reads.
The way to test that will be using an oscilloscope. Hook the negative wire to the bike chassis and the probe in the sensor output cable. Run the bike and let it idle. The screen should show something like this:

Or search the interwebz if somebody used the same speedo in the same model bike and how did they install it.

 

[Marbro_za]

sadly, its an ebay speedo , (I know, i know)

will ask them what they mean

thanks for the advice

 

[Shirou]

You can always invert the signal if needed, you need a CMOS IC (CD4049) and some cables, it can happily run directly from the bike's 13V power.

 

[Marbro_za]

I understand some of those words!
thanks