Cynic-al Posted August 6, 2015 Share Posted August 6, 2015 Ok so this is in my caravan not my land rover but it's the sort of thing an expedition vehicle might have... so that's my attempt at making it relevant! I know some of you are good at leccy stuff so I'm hoping you can help. My caravan has on board water, there's a level sensor so you know how much is in the tank which has never worked. Ok so it's not the most important thing but it annoys the heck out of me! Basically you press a button on a display, it sends 5v momentarily to a tank sensor then the display shows a percentage. Mine only ever showed 80% or 100%. I had a probe about and convinced myself it's the sensor so ordered another. It only ever shows 0%. The probes are sealed and I can't find a calibration screw on them or the back of the panel. I had a play with a variable resistor in line with the probe output and very slight adjustments to the output give me the full range. Problem is I'm not sure how the probe works. It's 3 wires which seem to be live ground signal but I'm not 100%. I've had an oscilloscope on and the voltage is fixed, it's not a pwm or whatever. However if I diconeect the probe and just put the variable resistor in its place the display just gives an error message. The output range required from the probe is probably 4 - 5v not 0-5v as you might expect. Any clues? I tried my local caravan centre who gave me the "I just want to charge you £200 to grease your bearings" sort of answer. I tried a main dealer who gave me the "we don't know what we're doing but we can randomly change every component at your cost" answer. I tried the caravan manufacturer who gave me the "go to your local dealer" answer and I tried the tank sensor manufacturer who didn't give an answer Quote Link to comment Share on other sites More sharing options...
robertspark Posted August 6, 2015 Share Posted August 6, 2015 Capacitance or conductance sensor? Problem is ... Depends on the ions in the water... (If it is one... Would have thought the gauge is the bit that needs calibrating though... Do you have a manual on the gauge or link to manual of manufacturer and model etc Just a guess I actually have never played with one though (maybe someone will come along who knows them in and out) Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted August 6, 2015 Author Share Posted August 6, 2015 The manual just says press button read water level. Don't know about probe type, I assume capacitance as resistance would only need 2 wires back to the display?, as I have 2 I could cut one up. Might not be that useful though as I think the circuit area is filled with some sort of resin. Quote Link to comment Share on other sites More sharing options...
robertspark Posted August 6, 2015 Share Posted August 6, 2015 Wouldn't do anything yet, I know nothing... Off to see what I can find... Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted August 6, 2015 Author Share Posted August 6, 2015 Thanks Quote Link to comment Share on other sites More sharing options...
robertspark Posted August 6, 2015 Share Posted August 6, 2015 Hmmm website for manufacturer here and info for same guage here for two tanks... Can't seem to find a manual for one tank, but if the manual is anything to go by I'd say you may have the wrong sensor .... As they may be product specific calibrated .... Edit (Muppet moment. RTFM.... Photo of the sensors has the same product code on them... Should be the same then...) http://www.cbe.it/en/content/pt522 Http://wwww.cbe.it Have a look through the other manuals on the site if there is anything else (I find more useful info on bog roll these days...) ... This phone is driving me crackers with autocorrect!! Quote Link to comment Share on other sites More sharing options...
robertspark Posted August 6, 2015 Share Posted August 6, 2015 Have you taken the guage out or off the wall? If so, there may be a calibration variable resistor screw hole on the rear of it as some of the conductivity level sensors seem to use a Wheatstone bridge arrangement, hence calibration adjustment required. If you're feeling brave and careful the back may be designed to pop off without breaking plastic pins etc and the same calibration resistor may exist inside I'll park my advice here as someone my know more when they logon later or tomorrow Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted August 7, 2015 Author Share Posted August 7, 2015 There is a screw on the old tank sensor which doesn't make any difference. I have had the display off but there are no signs of screws. If all else fails I will take it to a dealer for its next service and ask them to look Quote Link to comment Share on other sites More sharing options...
AMB Posted August 15, 2015 Share Posted August 15, 2015 You may find this link of use. It's for the PC200 panel which also uses the SPE probe. According to the leaflet SPE is a capacitive probe and the screw on the tank sensor is for minor adjustment. Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted August 16, 2015 Author Share Posted August 16, 2015 That gives me some things to try thanks! Quote Link to comment Share on other sites More sharing options...
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