Got it.  I was thinking it was ablyth, and not ab-lyth.  What a difference a space makes    www.lyth.se is the correct manufacturer.

Everything is in swedish, but I sent them an email anyways asking for information, and possibly an install manual on the unit.  The manual may be in swedish, but there are translation programs out there. 

Nope, they deal with mostly sailing rigging and supplies, nothing electronic.  I did take it apart, but there isn't much to look at inside.

I work in a avionics shop, and we recently got ahold of this strange directional unit.  Funny thing is, the guy who dropped it off didn't know what is was, and no longer wanted it.  We were going to trash it simply because it is hard to find a use for something that you don't know what it does, but I snagged it.

Now, what the heck is it?  It has 12V input in the rear, along with a 4 pin connector.  This may be a bit abstract, but maby I'll luck out and someone can point me in the right direction.  BTW, I tried googling Ablyth, and came up empty.  There is no ID tag or model number or anything that would identify it.  I'm not even sure it is aviation related, since it runs off 12V (and not 14, or 28)  Marine maby?

The winch has very simple controls.  You press a button which contracts a solenoid in the winch to draw off of the battery directly.  It spools in, and spools out under power.  There is no variability, it is either on or off.  I'm getting excited now.  I'll be sure to post my progress when I do go ahead with this, along with pics.

What about using a mechanical float?  Basically you use a float in the tank, and a rod slightly longer than 5m being fed into a plastic Cylinder above ground.  Add some markings to the tube, and you will know how much is in it by the location of the top of the rod.  A bit low-tech for sure, but it will work.  I'm sure you can get a series of sensors to go from the top to the bottom of the tank, and electronically measure the level, but this was the first thing to pop into my head.

Ok, I got this idea from another electronics forum.  I could actually have some sort of switch that is wired to my winch to automatically change the scale. What I have in mind is, when I am not using my winch or starter (the only things that will draw more than the 150A max rating), I'll stick with the default shunt setup. However, when power is applied to either the starter, or the winch, a solidstate switch, or possibly relay will switch in a resistor that will halve the meter sensitivity making its FS reading 300A (The website for my winch lists the max current draw of 320A at full load. And typical starters draw around 300A at most)

If I feel adventurous I could even paint on a second scale on the meter itself, but more likely, I'd put a little note, stating "x2 Start/Winch"

This could be doable 

I had just assumed that the shunt would be able to handle the excess current, and simply give higher than 50mV readings, and it was the meter I had to worry about.  I suppose I could do it that way, but the winch draw, and then the subsiquent charging of the battery afterwards (with my upgraded 120A alternator) is really what I was wanting to see.  I am really going for the "gee-whiz" factor, and would like to have everything connected.

Also, thank you for the warm welcome! 

Basically, I am installing an analogue ammeter in my jeep, and want to measure the charging current, and discharge current.  The meter I have is a 150-0-150amp meter (center zero), and uses a shunt to develope +/-50mV at full scale.  In other words, when the battery is being charged at 150amps, the voltage to the meter would be 50mV, and the reverse for negative.

My issue is this.  I have a winch installed on my jeep, and under full load, it can draw well beyond 150amps.  I wish to have a circuit which will intercept the voltage from the shunt, and IF it is within +/- 50mV, allow it to reach the meter.  If it is beyond this range, I want a LED to illuminate to indicate the 'beyond-range' condition, and protect the meter by not allowing the voltage to reach it, or idealy, allow only 50mV to show the full scale, AND light the LED.

I am an electronics technologist, but am many years out of practice.  Even just a few ideas to get the ball rolling would be great, and I can take it from there.  Any input at all would be greatly appreciated.

Rob D