I have a dutch motoryacht with three different tanks: Fresh Water, Wastewater and Diesel.
I wanted to replace my old analogue WEMA sensor with a modern solution, especially also to have the information integrated on the Cerbo GX. So I ordered thes Mopeka Pro200.
Installation, setup and integration for the Water and the Diesel were pretty straight forward. Wiring is not complicated, you just need 12V + and -, as the signal transmits via Bluetooth.
The real problems started with the wastewater tank. Unfortunately, my tank isn’t just square but has a rather special form. Nevertheless, I thought, using a Pro200 should not be too complicated, as the location for the installation is where the tank is at its deepest. A first try was promising, I got the vallues in centimeters on the Mopeka App and the connection to the Cerbo worked. So I fixed the sensor, which is done by the integrated sticky tape, using the included primer first to assure a good hold (and, most important, as it’s stinky wastewater, makes it tight against these odours…)
From there on, things went south. After that installation, the sensor delivered all kind of values, but nothing stable. Trying all the different settings in the Mopeka app and in the Cerbo setup didn’t help. So I contacted the Mopeka support. This was unfortunately a really bad experience. A first confusing thing is, that there are 2 different Apps for iOS, the Tank Check and the Co-Pilot. As the instruction said “Tank Check” I installed this one - just to have the supporter say, that’s the wrong one, you need the Co-Pilot. Ok, so reset everything, trying to delete the sensor from the Cerbo etc. Several times. When you add the sensor to the App, you have to toggle its power - so make sure, you have a easy access (in a engine bay of a boat…) or a switch. I got several confusing and not really helpful informations from the support, which didn’t match with what I found in several different sources. The conversation was too long to reproduce it here.
One problem seems to be the wastewater itself, which, by its nature is not clear and can, especially in this very warm summer here in Switzerland, develop bubbles and foam (and smell, but that shouldn’t bother the sensor). The good thing of the Mopeka would be that it has no moving parts, as the old WEMA sensor often got stuck and getting them out to clean is a mess.
As I really didn’t get any consistent level indications, I gave up in the end and ordered a Votronic Tank electrode. Which would have been the better idea in the first place. Removing the Mopeka was difficult, as it stuck really well on the tank.
This installation was pretty straight forward. You cut the electrodes to the exact length and then calibrate it. An important point is to fill the tank completely and then turn the calibration wheel on the sensor to the value of 2.20 V, as this depends on the length of the sensor.
The sensor gives you different voltage levels if the tank is full or empty. These can be read in the Cerbo Setup, then just fill the respective values in the “when full” and “when empty” fields. I recommend, to be sure, to empty and refill and reempty it twice.
BUT: unfortunately you can’t wire it directly to the Cerbo, you need the additional little Tank 140 box. And (important!) you have to make sure, that the ground wire of the sensor is connected to the same ground as the Cerbo. So the + of the sensor goes directly to the + of the boat and the - goes to the ground input of the Tank 140 AND to the common ground with the Cerbo. The signal wire (green in this case) goes in the Tank 140.
Conclusions:
- Mopeka Pro200 seem to be well suited for Diesel and Fresh water but not for Waste Water.
- The Mopeka integration in the Cerbo GX is easy
- The Mopeka support is lousy.
- Use a Votronic sensor for Waste Water, but take care to wire it correctly. It’s even cheaper than the Mopeka.
I hope this helps for decision making when replacing tank sensors.