MGL Avionics User Forum

Hi all,

Wondering if anybody can help. I have a Extreme EMS with the UMA tach sender connected to a Bendix S4LN-200 magneto. As best I can tell everything is hooked up properly. I have a Lycoming IO-360 Power, ground (to RDAC ground pin) and the signal to the RPM1 input on the RDAC. I am not getting any RPM readings. All my other sensores are reading good (Oil press and temp, Fuel press and flow, EGTs and CHTs)

Any help would be appreciate.

Scott

the UMA sensor needs to be supplied with 12V and may require a pull-up resistor to 12V to produce an output signal (something like a 2200, 3300 or 4700 resistor tends to work fine.
You can easily check them - measure the output using a voltmeter and slowly rotate the prop by hand (mags off !!!). You should see the voltage changing from close to zero to 12V and back again as you turn the prop confirming that the sensor produces a pulse.
Then on the RDAC just make sure you selected "high gain" and "Ballast OFF". Filter does not matter. Signal sends to be very clean. Turn the blue trimmer for RPM 1 about half way and it should work fine.

Were you able to fix your problem? I am having the same exact issue