MGL Avionics User Forum

I have an MX1 running firmware from April 2022, with an RDAC XG connected to a Rotax 912 uls engine. I have the original Rotax RPM gauge as well as the MX1. My issue is that at low RPM lets say 2,000 they both match but as you increase the RPM to say 4500 the MX1 then reads around 4700 and the difference increases with the more RPM, How do I synchronise the two is it by adjusting the sensitivity screw on the RDAC or is that screw meant to smooth out any erratic readings. My MX1 RPM is very smooth just reads incorrect compared with the Rotax gauge. Its not clear in the manual what the RDAC screw is for it just says sensitivity. Thank you.

darrenweston wrote: ↑Fri Jul 14, 2023 1:13 pm I have an MX1 running firmware from April 2022, with an RDAC XG connected to a Rotax 912 uls engine. I have the original Rotax RPM gauge as well as the MX1. My issue is that at low RPM lets say 2,000 they both match but as you increase the RPM to say 4500 the MX1 then reads around 4700 and the difference increases with the more RPM, How do I synchronise the two is it by adjusting the sensitivity screw on the RDAC or is that screw meant to smooth out any erratic readings. My MX1 RPM is very smooth just reads incorrect compared with the Rotax gauge. Its not clear in the manual what the RDAC screw is for it just says sensitivity. Thank you.

The RPM works by counting pulses on the input, the sensitivity adjust sets the minimum pulse height for the counter to see them.
Threshold too high (sensitivity too low) and you will miss the pulses, threshold too low (sensitivity too high) and you will start triggering on electrical noise.
Accurate at low RPM but erratic at high RPM generally indicates it is set too sensitive and starting to trigger on electrical noise on the RPM input.
Try adjusting the sensitivity so it is only just triggering at low rpm and then see how it behaves across the range.
If the RPM indication is stable but 'wrong' (compared to the Rotax gauge) across the rev range...perhaps the Rotax gauge is the problem?

Thank you for the comprehensive answer to my question I will try his out at the weekend.