Maretron N2K tank level calibration, nice!

... written for Panbo by Ben Ellison and posted on Oct 2, 2007

Maretron tank calibration cPanbo

I recently added tank level and rudder angle info to the lab’s NMEA 2000 network. In both cases this involved wiring a Maretron Adapter to a standard analog sensor. N2K skeptics will no doubt gleefully point out that the two sensors—a VDO for the rudder, and a Teleflex for the tank—together cost about half the $195 list price for either the Rudder and Tank Adapter! But consider what I got in terms of a bigger boat system.

Just connecting each adapter’s two wires put the tank and rudder information on the Raymarine E (below), on the two Maretron displays in the network (of course), and, get this, via N2KView onto my home megayacht Ethernet/WiFi network where I can monitor it anywhere (more on N2KView coming). Even the Garmin 5212 can use the fuel level info as a gauge, though it can’t seem to show it as percentage or in total gallons, and it doesn’t display rudder angle at all (but supposedly that’s all coming).
   Perhaps even better is the easy yet sophisticated calibration possible, particularly with the tank adapter. Of course you do need a Maretron display or its USB Gateway and the N2KAnalyzer/DSM simulator software discussed recently. Check out the full screen shot, which shows me in the act of custom calibrating a (pretend) odd-shaped tank by recording up to 16 data points as I “fill” it. I’ve also opened a window on the “Fluid Level” PGN the Adaptor is sending. You can see Tank Capacity, Level (0 before I began the calibration routine), Type, and Instance. “Instance” is how you deal with multiple tanks and, though neither the E nor the 5212 give you much control over this stuff, both did presume Instance 0 info meant Fuel tank1 and Instance 1 Fuel Tank 2.
   Also note the window on the lower right of the screen shot, which is showing the PGNs that the Raymarine E is sending into the network. I was pleasantly surprised the other day to see that—though it’s getting all the underlying data off the N2K network—it’s still adding back Set and Drift calculations because they aren’t already there. Never mind for now that nothing else on the network will display the Set and Drift, they could! Perhaps I’ve gone a little too deep into N2K minutia here, but those of you still with me might like to know that NMEA recently put up a PDF list of standard PGNs. Enjoy!



Well it's interesting to me because I'm facing this issue right now. So this begs a couple of questions:

1) The calibration data is stored in the sensor or in your case the adapter. In either case it's an N2K interface. Is this calibration via standard N2K protocols, or proprietary, i.e., will the Maretron s/w allow calibrating of any N2K tank sensor? Like one from Offshore? I'd gladly buy a Maretron display to connect to my Offshore sensors.

2) Now that we know how much, or little, fluid is in the tank, where is the N2K compatible device that will use that information to apply some logic and turn a pump on or off?

Posted by: Russ at October 2, 2007 9:25 PM | Reply

Very interesting.

Posted by: Dan (b393capt) at October 3, 2007 9:29 AM | Reply

1) My understanding, Russ, is that rudimentary calibration commands ARE built into NMEA 2000, but they've hardly been utilized. Apparently the Standard allows PGN messages, like fluid level, to be reversed and thus reset. So a tank adapter/sensor might think that x voltage equals y tank percentage, but then standard command line tells it, "Nope, that's z percentage, and remember that!" So while a whole routine like Maretron's 16 step odd-size tank custom calibration is not part of the Standard, it just might work with Offshore's PGNs. But maybe not! I'll ask Maretron.

2) I don't know of anything that does this sort of thing yet, but it is certainly possible.

Posted by: Ben at October 3, 2007 9:58 AM | Reply

The more I read about these Maretron products, the more I like (and very complete .pdf manuals and datasheets from the manufacturer, there's plenty to read and learn!).
Ben, I wonder if you could comment on the Maretron display's brightness/dimming and contrast, as well as the overall "feel" of the interface. Are these really useful standalone, or would you class them as being mainly most useful connected to a PC, external display/interface (such as your Raymarine E)?

Posted by: Yuri at October 3, 2007 12:00 PM | Reply

Notes from Maretron:

With regard to where is data stored, Maretron always stores configuration data in the sensor, that way not all displays on the boat need to be setup to understand configuration data (i.e., configure the sensor from one display such that the sensor stores cal data and it sends correct data for all other displays to use).

With regards to standard calibration, most of Maretron’s gear can be setup by other manufactures as we use the standard NMEA 2000 mechanism for configuring. For instance, anyone can set the tank type (fuel, waste, etc.), tank instance (fuel 1, 2, etc.), tank capacity.

Unfortunately, custom calibration for odd shaped tanks is outside the current scope of NMEA 2000 common configuration, but even this is being talked about (i.e. we actually do what you say in your post “x voltage equals y tank percentage, but then standard command line tells it, "Nope, that's z percentage” although we wrap all those x voltages and z percentages in some proprietary PGN to make the whole cal coherent).

I must add a caveat, and that is very few manufactures understand, or if they do understand, they are not implementing standard configuration. We openly support standard configuration and I think you will start to see other manufacturers implementing it soon. Some other things that any other manufacture could program within Maretron products to name just a few:

DST100 – Keel offset, reset trip log, turn on and off PGNs
GPS100 – Turn on and off WAAS, set antenna altitude and many more GPS parameter, turn on and off PGNs
WSO100 – Set humidity, pressure and temp offsets, turn on and off PGNs
TLA100 – type, instance, capacity

Posted by: Ben at October 5, 2007 12:12 PM | Reply

Yuri, I'm not crazy about the original grayscale DSM200 monitor; it's not very bright and its not very fast. The new color DSM250 is much faster, and may be brighter (I haven't had it long), but Maretron has so far hardly made use of its colors.

I think it's neat that you don't have to buy a Maretron display to see the data. Or even to do the calibrating, as long as you or your installer has a USB Gateway and the DSM simulation software.

Posted by: Ben at October 5, 2007 12:18 PM | Reply

I have a Garmin GND 10 that has a USB interface. I believe it talks with the N2K network (not sure). I would love to install two Maretron N2K tank level monitors but have balked at the additional price of the Maretron USB gateway just to program the units for my 'unusual' tank configuration.

My question is can I use the Maretron N2KView with the Garmin GND 10 to program the tank monitors?

Also, it would be nice if a vendor would program the tank monitors for your irregular tank before shipping them. You could provide the data and they could program the units before shipment. This could be an extra cost (~$20). $200 - $300 just to program the tank monitors seemed high.

Posted by: Peter at January 31, 2017 7:39 AM | Reply

I failed at using the maretron tank level monitors successfully for various reasons of tank geometry (which is hard to know what the inside looks like).

The good folks are Maretron pointed out that the fluid pressure monitor, FPM100, in their product line is often a better choice. Looking it up for this reply, I see they now offer sensors that can drop in from the top of the tank, useful when it's difficult to drill a hole for the sensor in the tank bottom.

When the sensor sits on the bottom, your ability to know how close to empty and close to full you are is greatly improved over using ultrasonic measurement.

In regards to your comment, I have to venture torwards guessing here .. if your not using a Maretron configurable display or maretron nmea2000 interface to program the fpm100, if you use just one sensor you may get by if your display will show something and then work out what readings are equivalent to tank near empty, half full, and full by adding fluid to the tank while checking readings. My guess for multiple decices you will need to program the devices at least a little.

Either way the good folks at Maretron can tell you for sure, and maybe an installer can program your device.

Posted by: Dan Corcoran (b393capt) at January 31, 2017 12:40 PM | Reply

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