EMS-2 and rpm errors on Hirth F-23

[scotts97385]

I have a EMS-2 installed on my experimental and may be getting a error in reading high rpms. I think the lower rpms between 1500-4500 are ok but anything much higher seems to be inaccurate. I understand the output voltage on the Hirth F-23 at higher rpms may get to nearly 60 volts, is it possible that this may be the problem? How can I resolve the issue if it is?

[sparxfly]

Have a look at section 10.3 of the EMS-2 manual.
Sounds like you will need to put that 220ohm resistor on the RPM signal line to load down the input signal, and then tweak the sensitivity to get the RPM indication just triggering at idle but not firing on noise at WOT.
There is also the option of setting the high frequency filter ON as in 10.3.2.
If still no joy you will need to look at a resistive divider on the RPM input- say a 1Kohm/2W resistor in series with the 220ohm to ground, reducing the input level to ~1/6.

[scotts97385]

Thank you! I have yet to get a answer from MGL support on this issue.
Would the 220omh resistor be run in series to the EMs-2 on the blue wire or branch off to ground to reduce the noise?

[sparxfly]

Would the 220omh resistor be run in series to the EMs-2 on the blue wire or branch off to ground to reduce the noise?

From input to ground.
Have you got the EMS-2 manual? Download from http://www.mglavionics.co.za/Infinitec/ ... 0EMS-2.pdf

[scotts97385]

Thanks, you have been very helpful!