MGL Avionics User Forum

Hi, I am installing a BLAZE EMS-2, however I am stalled at the TACHOMETER connections. There is only one, for the signal wire. The analogue Vdo gauge, which I am replacing had 4, two of which were power, leaving 2. Is there a simple way of figuring out which wire should be connected? and am I right in thinking that because the EMS-2 has its own power and earth that all the other gauges that I will be connecting do not need their own individual power and earth now?

Any comments gratefully received.

Start at the other end - what engine and RPM pickup are you using ? If a 912UL(S) you have two wires blue/yellow. Connect one of them to ground and the other is you RPM signal for the EMS. In this case (Rotax) you also need a ballast resistor (built in to the VDO) - we use a 220 ohm resistor (wired between the two RPM pickup wires - wattage does not matter, anything goes).

Hi, and thanks for your reply, the engine is jabiru 2200, I THINK it is a HALL sensor mounted to count the revolutions of the flywheel to give RPM. I have used a voltmeter to trace the two wires coming from it, they are black and red, the maintenance manual says connect both to the VDO gauge, with a very nice picture of the back of a VDO gauge showing where they go. Further searching shows that the red wire goes to the signal input, so far so good, but then the black wire, which I can only assume is a ground to earth. I am guessing here, any opinion gratefully received. thanks.