MGL Avionics User Forum

I'm using the floscan fuel flow meter and wondering if it needs the 5v jumper with resistor like in one of the older ff gauge manuals. Only want to wire it once. Thanks The rdac I'm using is the rdac-xg.

Like many of these flow senders it needs a pull up resistor - usually to 5V or 12V. We tend to recommend a resistor in the 5KOhm range but be prepared to experiment - we have come across a few lately that don't seem to be able to pull even a relatively small current load to ground properly so you might have to use a larger resistor value.

Easiest way to be sure - just blow lightly into the inlet to get the impeller turning then measure the output voltage when it stops - it will stop either at the high or low level. Make sure the low level is 1 volt or less.

Could I start with a 4.7k?

yes

i'm back to doing this, the 4.7k did not work correctly so should i go to say 10k?

A 4K7 to 12V should give you a really good signal - if it does not your flowscan is most likely toast. I really would recommend you beg, borrow or steal one of those portable scopes and hook that up to the output of your flowscan and let rip - you should see a nice solid pulse train with flow - the faster the flow the higher the pulse frequency.

I you see nothing (either solid 0V or 12V) you have a broken flow sender. Assuming of course your resistor is correctly wired (that provides the high voltage (12V) - the sender itself is really just a switch to ground (zero volts).

Ended up getting this working. I had my k factor set way to high. It now reads close to normal