Water Gauge (again)

Reading these points got me wondering how the analogue water level gauge works on my van. Will it be the good old fashioned float and potentiometer system? 
In common with the modern digital set up, it's far from 100% accurate, for instance still showing full when nearer only three quarters, but after that it's pretty good.
The thing is, it's never failed to work in 13 years of use, so why abandon a tried and tested system?

It's pins set at different heights in the side of the tank Al.

If the water level is anywhere above (say) the 50% pin, but below the 75% pin, it will show as 50% - even if it's only a cup full less than 75%, 'cos it can't quite reach that pin.

By the same token, as soon as it drops half an inch below the 50% pin it will show as 25%.

With the previous van I went to the bother of filling up from empty with the watering can, and noting how much had gone in when the level indicator changed up (as it were). Then I knew the minimum amount of water we had left at any indicated level.

Have I bothered with this van??   I just top up every day or two, then apart from anything else it's a quick and easy job.

I thought it was 2 prongs at different heights coming down from the top of the tank,

Ours was faulty on our 2008 Nuevo when we purchased it and we had it replaced with one of these.

http://www.ebay.co.uk/itm/CBE-FRESH-WATER-TANK-LEVEL-GAUGE-probe-motorhome-conversion-boat-camper-270572-/132276497443?epid=1023195747&hash=item1ecc4b2c23:g:jBcAAOSwzrxUvn0T

 Then I had the MES control panel modified so it thinks it has a full fresh water tank so allowing me to keep the alarm for the waste water, this seams to be working fine. 

Just had trouble with my sensors reading zero with a full tank.  Marquise tech has shown me how they are positioned and to replace need hours so he drilled new holes.  All working well again and if they go can be replaced easily
Gef

I had a Hymer for 10 years. It had sensors in both fresh and waste water tanks. They were 5 long probes of different legths mounted in th etop of th etank on a baseplate and connected to an analogue meter.  I never had an incorrect reading - waste or fresh.  I believe that there are two problems with the Sargent system - one is the scaling but I suspect that the Sargent chip is too intolerant of resistance caused by the scale.  Having said that, taking off the bottom cap and reacj=hing inside with a clean Scotchbrite did solve mu problems for a month!  Now back to erratic readings - which reinforces my suspicions about the lack of tolerance of the Sargent metering chip.