Sometimes when You are underway in a non familiar environment with limited access to facilities (internet for probe data etc.) and Your mind deeply focussed on a problem even obvious hints are helpful, so thanks for Your comment.
I had to learn the hard way, but I solved my problem and I want to give You a feedback for further builders, as it is quite straightforward to install a DYNON EMS to the Princeton probe with 3 connectors – and I assume it can be easily taken over to the 2 connector version.
In contrast to what I have assumed, the capacitive probe does not deliver a voltage at its exit; independent of the amount of fuel in the tank voltage You measure there is always 0V.
It seems to be matched with the conventional Datcom (A/S Nr. 100177) indicator; connected with this voltage varies between 3.6V (full) and 7.2V (empty) (at currents greater than 500mA!). With the two potentiometers on the Princeton probe You can adjust the full and empty states respectively. You can easily monitor this voltage setting Your DYNON to “type 2”.
It can be concluded that the Datcom indicator includes something like a constant current source; varying voltage means that it has to origin from varying resistance according to Ohm’s law.
So the Princeton probe delivers varying resistance as a function of the filling state. Without an external Datcom as current source, You may set Your DYNON to “type 1” as for resistive (float type) probes.
It is however important to know that the combination will not work until You have done a full / empty calibration at the pots of the probe with only the Datcom indicator connected to it first. It seems to me that this is necessary to bring the probe in its range of operation.
Knowing that things are easy:
1. Temporarily connect Datcon indicator only to Princeton probe
2. Fill tank, adjust the little “full” -pot on probe to 1/1
3. Empty tank, adjust “empty” – pot to 0/1
4. Disconnect Datcon, connect DYNON “type 1”
5. Fill up tank in portions as the DYNON software suggests
Done!
