question

neil-mclaughlin avatar image

Cerbo GX Water Tank Level Sensor Recommendations Needed

Hi Folks,

I am excited about the tank monitoring capabilities of the Cerbo GX but I see so many different and highly technical posts. I really am hoping that by now there is a "plug and play" recommendation. I have three fresh water tanks and would prefer outside sensor install but whatever is proven and most accurate. I have access to all tanks from the top and sides. I also have the Cerbo connected to a BMV-712 and a Multi-plus inverter by the appropriate wire cables and then on to the Raymarine Axiom Pro(where I will hope to read the water levels in addition to the phone app or VRM).

Appreciate your recommendations.

Neil

cerbo gxtank monitor
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10 Answers
dfraizer avatar image
dfraizer answered ·


I have a similar setup and I installed senders by KUS USA. I am monitoring water, waste on my cerbo GX and plan on adding a KUS USA analog/digital sender for fuel so that I can monitor fuel via my nemea 2000 network on my axiom pro. I tried a bunch of senders and the KUS USA are the easiest to install. Great to deal with

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Thanks so much. Can you please provide more detail on the model and connectivity to either the Raymarine Seatalk backbone or direct to the Cerbo from each device, etc?

Hi do the KUS senders plug directly into the Cerbo or do you need some kind of adapter? Thanks
luis-gomezcala avatar image
luis-gomezcala answered ·

Hello from Dublin,

I have a similar setup as yours, the best option would be a pressure sensor which can be plugged in outside your tank in the pipeline. The problem is Victron only supports resistive tank sensors fitted inside the tank or external which are rather expensive. However, if you get in contact with Oceanic systems in the UK (manufacturer of Victron resistive senders) then you will be able to get a 4 20ma pressure adaptor which interface with your Cerbo directly. I wished I knew this before purchasing the very expensive Victron sensors. Here is the link:

https://osukl.com/pressure/

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mvader (Victron Energy) avatar image
mvader (Victron Energy) answered ·

Hey all, within 2 to 4 weeks we’ll be shipping the first batch of our new GX Tank 140.


GX Tank 140 is an accessory to be used with a Victron GX device. It can connect up to four tank level sensors with an output between 4..20mA or 0..10V. Connection to the GX Device via USB.

Highlights:

  • Channel 1 and 2 feature a fused power supply from the Vin connection terminal; requires an external power supply
  • Channel 3 and 4 feature a built-in 24V power supply for the tank sensor. Power is coming from the USB.
  • Configurable upper and lower limits, use this to connect (for example) a 0 to 5V sensor.
  • Configurable averaging filter (1 to 60s) to dampen fluid movement.
  • Faulty sensor detection: when values are out of range an alarm will be raised.
  • For marine applications: yes the GX Device can transmit these tank levels out on N2K network to be picked up by other displays such as an MFD. For details, search for NMEA2000-out in the Cerbo GX manual.


End-user C EUR price ex VAT is EUR 100



b9bbcfcd-5549-498a-b78d-f728f2e0bc10.jpeg


5 comments
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Hello mvader,

This is truly exciting and an answer to this popular expectation of Cerbo GX and GX users. Looking forward to this product being available through the Binnacle in Halifax. Also, please advise if you can ship direct to a few of us to install and test.

Thanks,

Neil

Hey Neil, good to hear your enthusiastic; I am too!

Can't help with the samples, sorry for that. Tell your dealer to keep an eye out on E-Order on the "new products" list, they'll show up there soon.


Sweet. How can I get my hands on one of those?

Hi mvader,


I just got the GX Tank 140 but wondering if you have a list of recomended sensors ? I am looking for a pressure sensor to be connected externally and ultrasonic sensors for the waste tank


Thanks a million

I'm trying to understand if I need this device. I will have a single water tank in a vehicle that, I assumed my Cerbo GX would be able to monitor without another accessory in between the tank and the Cerbo. Is there a water tank sensor that Victron recommends that can just plug directly into the Cerbo?
Wes Humpage avatar image
Wes Humpage answered ·

Just purchase a 0 to 5 psi sensor from eBay

$26 each

Wire the ground to the lower terminal and the positive the top terminal (next input along) and the sensor wire to the top terminal (input)

Just use the custom sensor setting to set you scale, if the impedance of the sensor takes your measurement outside of the Cerbo input just use some resistors to either pull up or pull down the sensor wire (normally a 1k ohm will do it)


it’s really easy. I have 4 setups (8 tanks) running like this

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The pressure sensor is a 5PSI

https://www.ebay.com.au/itm/1-8-NPT-5V-5-200-Psi-Steel-Pressure-Transducer-Sender-Sensor-Oil-Fuel-Air/303860265448?_trkparms=ispr%3D1&hash=item46bf7bb1e8:g:FbEAAOSwhQpdrWpw&amdata=enc%3AAQAFAAACgBaobrjLl8XobRIiIML1V4Imu%252Fn%252BzU5L90Z278x5ickkpFtSR0CGv%252Bh98r8Yb9quS2RiaQcSSxMoDUuC5wkCAPQunp5H7mVW0Ju2dwOblcqrb5D1sMgRDOuLVzMoAfBe9JR1ZBdHqoTKWQnI3hzMvVIoSHjw2B%252FkT66He6G7QJG1JjajbbX7puRxWMoobhB4xjfMKfhKJivgJcQUQe3q4xtpnkEUNnp3JAylfJ6pytpsSK5LmpSfpWo6QAW4aT5jM6vup35IJ0D89vEiAT86pzQfi%252BleAlF60UHB3oYDjnhUbWp7dUg68%252B6rKmw39Wdas9k16vEkw7qiBKigm7LgsYvZfsWdR6%252FHqDX%252BLgArpJbyJnG9bFjFlDto4p2H2ol9ntAjDRdxcARuf9NH37XbDx0m2q9ANGLU90T1PguY76nRo6%252Bp3UipQSlTrEm8gvIeiciXyryJQWxKpGFzAykKiwTM5mdt8lmWk0WKecudOFe7upcHxn3uPv43sZsNO9N8qo9Cq9JJfjXUYSxxAM5MkYmzf4vKjgPGyyNCmnlEZVjsHoJlvHdPISC85Btjd6Qo1jzYV%252FLTS86%252Bpj6Icu3xQ4MRUzLUORH6Bs%252BQZZP%252Bhi7L7pK0yJbqUCm2RJ1tSG5kvHj0ZXr0pWPmlwzsdRS3Kv5%252B7ezXRyFfUIT%252BMRSFOMUmtDpSk0cdrzCjMD5z8GM21sGYcrZ70%252FWVjNQWOMnCg4%252FyNXvMi%252Fseb7fSMMRt61UvL3LASwzkpG3gXImzO7wICcVS9NyKRx2ucfTK2ETTRmV1XwAJDA%252FFv8da0fHvZHfZX3LYeMNguE0K8DwSiDTe6iHejO0AhKscHxnWI5LkfPA%253D%7Ccksum%3A303860265448f907765cca3c4c2c8309eb440899122c%7Campid%3APL_CLK%7Cclp%3A2334524



Being a resistive input it can float around a little bit but from my exp its accurate enough.

Black wire on the 0V (back terminal)

Green wire on the input (front terminal)

Red wire on the input beside (2nd front terminal)



Just play around with a resistor between green wire and the black wire (depending on the impedance of the sensor you buy)


It works well enough for me

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1615264470235.png (63.2 KiB)

Wes,

Excellent work! I ordered the same (or similar?) sensors for my skoolie conversion. My 5 lbs sensors are saying 5v input voltage. The GX Tank 140 can supply 24v through the last two ports. Can these 5 lbs, 0- 4.5V linear voltage output sensor handle the 24v or should I supply them with a separate 5v feed?

Thanks again for the idea! Looking forward to seeing my tank status in my Venus GC PI!

Jim

Wes, please let me come back to this interessting hint to check my understanding.

You directly connect the 5psi pressure sensor to the Tank GX 140 ?
(With some resistor-based adjustments)
How does this sensor deal with atmospheric pressure changes ?
Are there any compensations (differential pressure) ?
Or with other words: will the displayed level change while you drive up a hill with the RV ? ;)

Great Wes, I dismissed this idea as someone else in the community was unable to make this setup work. If you don't mind, please post a photo to have a look of your connections. Definitely, you will save serious money using transducers wired directly without additional converters

Hi @Wes Humpage a bit lost by your reply. What sensors are you using? are they a 0 to 5V type sensor and if so how have you connected directly to the Cerbo GX as the manual specifies that the tank level inputs need to be resistive?

I posted the comment above, its a $30 solution. Works well enough.

I wondered if you can elaborate on the above comment.


Im my situation I am trying to get a fuel sender that has a range of 0-190 ohms. I have plugged into a new GX tank 140. I am only seeing readings in mA and not Ohms.

And the range is 17mA bottom

And 20mA at top.

Do i need to add a resistor to broaden the range.


Thanks in advance for any help


Resistive level sensors are wired directly to Cerbo and Venus GX. The GX Tank 140 is only for current 4-20ma and 0-10 Volt sensors.

Pressure sensors 4-20ma are ideal for measuring tank levels as they can be installed outside of the tank or even at a short distance provided the position is still representative of the height of fluid.

Ideally, you need to match the sensor range to the expected height of fluid to gain the highest resolution. i.e. 0-0.2 bar for less than 2m head The settings allow individual tank and fluid calibration.

jesseafuchs avatar image
jesseafuchs answered ·

I apologize if this is a basic question but Im still trying to compile all of the vast victron knowledge.

Will this bad boy be able to assist in connecting the Garnett Seelevel Tank Senders to the Cerbo for monitoring?

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pau1phi11ips avatar image
pau1phi11ips answered ·

Just search for this on eBay, there's loads are different lengths:
"water level sensor 0-190 ohms"

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Rene Mullie avatar image
Rene Mullie answered ·

I did some testing with various sensors; the best solution and plug&play level sensor for the GX Tank 140 is this differential pressure sensor:

https://www.aliexpress.com/item/4000096662581.html?spm=a2g0o.9042311.0.0.22d14c4dshbEiI

A well made stainless steel heavy IP68 housing, output 4-20mA 24Vdc power directly from GX Tank unit. Connect red cable from sensor to 24V output on GX Tank, black cable to IN; set Cerbo to right sensor type (4-20mA) and it is operational! Price: 42euro

Very accurate; I installed the 0-1M version in a 35cm high 111L fresh water tank on my RV and, after calibration, it is so amazingly accurate; less than 1L accuracy to the last cm of water in the tank!

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Hi Rene, I got a similar one. The difference it has threads meaning they can be installed externally in the pipework

However, I was only able to make it work but using 3 cables +,- and Ground . Were you able to install using only 2 cables + and - ?

The sensors will be installed 20 metres away from the GX so I would prefer one cable run if possible


https://www.aliexpress.com/item/1005002809447897.html?spm=a2g0s.12269583.0.0.2a9f392aUrdu7f

Yes, the sensor I metioned works over 2 wires in conjunction with GXtank.

Nice recommendation! How do you mount this sensor in your tank? Noticed it doesn't come with a base or anything that can be attached to the tank so it doesn't rattle. I am considering it for my RV as well.


@Rene Mullie


Thanks

I did not mount it, the sensor just lies on the bottom, never heard any rattle... The sensor is quite heavy.
Got it. Thanks!
thegrandpoohbah avatar image
thegrandpoohbah answered ·

Just to be clear....the 5 psi pressure switch that Wes used was connected directly to Cerbo GX???

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Thierry Cortassa (Victron Energy Staff) avatar image
Thierry Cortassa (Victron Energy Staff) answered ·
I did some testing with various sensors; the best solution and plug&play level sensor for the GX Tank 140 is this differential pressure sensor:
https://www.aliexpress.com/item/4000096662581.html?spm=a2g0o.9042311.0.0.22d14c4dshbEiI

i test it in a 1600l water tank and it's look very good and simple to instal !

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Wayne avatar image
Wayne answered ·

Hello from New Zealand

I'm using the new tank 140, which is plug and play with the sensors available from Safiery in Australia.

I have a pressure sensor running on my fresh tank, about to instal a pressure on my genset fuel tank, and two ultrasonic bottom mounts one on the grey waste tank and one on the RV diesel tank, I love that they are plug and play, the ultrasonic works on composite and steel tanks, I'm doing the diesel tank as we park for periods in the winter and our heating is diesel from the truck tank so I like to be able to monitor without having to go to the cab.

https://www.safiery.com/tanks

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I'm thinking about switching to pressure sensors.

Am I correct in assuming that with a pressure sensor (like those from Safiery) I only have to calibrate the full 100% and empty 0% level, even if the tank has an irregular shape (wider at the top than at the bottom, one side higher than the other, one end higher than the other) or do all possible intermediate steps also have to be calibrated with this type of sensor in order to deliver the highest possible accuracy?

Wayne avatar image Wayne Stefanie ♦ ·
Hi Stefanie

You have both options, set your empty and full readings.. or up to 10 increments for irregular shaped tanks.

Cheers

Hi Wayne and thanks!

Yes, I know both possibilities. My question was more in the direction of whether it is sufficient when using a pressure sensor (4-20mA), is the Full and Empty calibration enough with an irregular shaped tank and still get accurate readings for anything in between or does it need the 10 increments .The latter would require the complete emptying of the diesel tank and then determine a value for each of the 10 increments, for example by measuring for each 10l when I fill up. I wanted to avoid that.

I have no experience with pressure sensors at all, just thought that these are easier to deal with.

Wayne avatar image Wayne Stefanie ♦ ·
Hi Stephanie

To get accurate you really need to get the tank empty or as low as you are comfortable and set that as your "0" the full is easy.

The issue you have with just two readings is that if your tank is shaped into the hull and lets say for arguments sake your tank is 500mm top to bottom but is wider at the top and narrow at the bottom. So the sensor will read 50% when the fuel is at the 250mm mark, but you may only have 30% left due to the tapering tank size. Mine are no issue as all my tanks a cubic. In my experience you will face the same issue with resistive or pressure or ultrasonic.

I would recommend, running the tank as low as you are comfortable, fill the tank, divide the resulting litres by 10, on the next fill using a measure fill the tank in ten measures noting the readings and program accordingly.

Hop that helps

Hi Wayne,

many thanks for the detailed information. That's exactly what I wanted to know.

I thought that even with an irregular shaped tank a pressure sensor only requires two calibration points. But if I think about it now, it doesn't make any sense, of course, because the pressure in my tank doesn't change linearly.

At the moment I have a simple level gauge with a float (driving a potentiometer) for my diesel tank, but it is extremely inaccurate, especially when the level is below the wider part in the top of the tank. In addition I have an NMEA 2000 adapter, which then delivers the data to the boat network. I can also provide this with many calibration points, but so far I have always tried to avoid the effort. Well, I guess I'll have to get over it then. I ordered this https://www.amazon.de/gp/product/B07NWM3TNT/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1 and have to empty the tank anyway before I can mount the sensor.


Wayne avatar image Wayne Stefanie ♦ ·
Hi Stefanie

Your sensor looks very similar and is also similar to the Safiery 3 wire units we use, are you going to run it through the Victron tank140, be interested to hear how it goes and if you are happy with it..

Hi Wayne,

I was looking for the sensor from Safiery because it has a much nicer form factor (not quite as long as the one from Amazon). Unfortunately I couldn't find it here in Germany.

Yes, I will run it through the Victron GX Tank 140 (also difficult to get these days but I found one in the Netherlands). I'll make some tests here at home before I install it in the boat's Diesel- and Freshwater tank and report back here.