Oil tank level monitoring.

After having a near miss at my summer house last week I am looking for the ways to detect when refill is needed and set a rule to send email.

I have ELK M1 Gold.

Thank you.

Alex.

A "no touch" way to monitor fluid levels is to use a pressure transducer.  Freescale makes one that is inexpensive that is 1 to 1.5 psi which can measure several feet of fluid depth.
 
With the tank empty or if there is a valve that you can close, you put a t-piece in your draw tube that comes off at or near the bottom somewhere to the side of the tank.  To the t-piece attache a piece of pipe and run it straight up to a level that is a few inches above the top of the tank.  You put a nipple on the top of that tube and connect the transducer with a short piece of tubing.  Vacuum tubing from the auto part store works well for this.  Then when fluid is put in the tank, it will partially fill the tube compressing the air in the tube and raising the pressure in the tube.  The pressure transducer will read the pressure and report a value between .2 and 4.8v as the pressure increases.  You fill the tank and note the pressure when full.  Then it is just a linear scale between that number and .2 from full to empty.
 
You can use an Elk zone to measure the voltage off of that transducer and have it send you an email when it gets below some number.
 
Total cost for a project like this probably is in the $35 range.  The transducer is about $20 as a one-off purchase including shipping from digi-key, and the iron pipe t-piece, a few feet of pipe, a nipple, and vacuum tube should cost but another $10 or $20.
 
I've seen people describe using ultrasound to measure the distance to the fluid from a fixed point (like the fill port).  Also a float of some sort would work.  Probably both of those cost more, and may or may not be more work depending on if you can buy a pre-made purpose built device.

I mentioned the MaxBotix ultrasound in another thread, but it could be problematic interfacing it with the Elk as it's analog output is to small and you would have to get an expansion for the serial stream.
 
I'm wondering if a float would indeed be the best way to go as you could pretty much dictate its excitation voltage and directly interface it via an analog input into an Elk's zone.  Of course, I don't know if they make these floats with the viscosity and travel requirements for this particular application.
 
I do like Lou's suggestion above as it seems to have a very high feasibility rating!

They make lots of interesting stuff for oil monitoring, not that I have used them or even use oil for heating.
 
For examples.
 
float
http://www.sybasystems.com/FM%202%20sender/fm%202%20sender.html
 
meter
http://jerman.com/oilmeter.html

That 'magneto-resistive' looks like a nice option SDA but I'm wondering if its float can operate with a thicker oil viscosity.
 
EDIT:  Should have read further, by 'fuel' they do indeed mean 'fuel oil'!
 
http://www.sybasystems.com/Fuel%20Minder%20II/fuel%20minder%20II.html

I have pondered this a couple times, and one of my options I have come up with is just using the existing float style gauge in the tank, add a small magnet to the vertical level indicator and some window contacts at each level I want to sense.  however this is a small 2 inch gauge and would need small contacts and a light, magnet so not to effect the gauge due to weight.  
 
 My Gauge example (its just the vertical site glass style with 4 divisions)
 
 
No as for level sensors mentioned by other members, I am unsure of the output accuracy due to any sludge at the bottom of the tank. I know my pickup tube is not at the bottom because of that I think it is an inch or so up.

Seeing some of these probes gave me ideas. Thanks for the links. I plan on using a homemade sealed reed switch like a security contact with a magnetic float of some sort. I don't need to know exactly how much fuel is in the tank. I only need to know when it is time to order more. I run our ordering closer than most of the people I know. I have got it to the point that with a 330 gallon tank our deliveries end up being around 300 gallons which is almost on "E". I think coming up with a homemade solution that I can adjust would be my best bet.

I am also thinking about a more K.I.S.S. method of using something like this:

http://www.sybasystems.com/Oil%20Watch/oilwatch.html

Consider this.  When it comes to fuel oil, prices swing wildly at times.  It may suit you better to actually know the real level and watch prices.  Sometimes filling a half empty tank when prices are low is a better plan then waiting until you have only a few days of fuel left and you are stuck buying at spot price.
 
And it just occurred to me that the plan I gave you could be made dramatically simpler.  
 
You don't have to cut into the line exiting the tank and put a t-piece in.  You can simply take a pipe that is longer than your tank is deep, seal one end with a nipple and put your transducer on it.  Then open the fill on the top of the tank and stick the tube down until it is just above the bottom.  Secure at that height and you are done.  Probably you could figure a way to make it part of the fill cap.  Maybe drill and thread a hole in it.  
 
The transducers of which I speak are made with the purpose of measuring fluid levels in mind.  In fact they give examples of doing such things in their literature.

Lou. Also considering your suggestion of a pressure transducer. Our fill has 2 90 degree bends so one of the spare, capped fill port openings will have to work.
 
We do typically buy low as we have timed our fills so that at least one fill is when oil typically drops at the end of the summer. This year was the first in a while where it actually went up due to some "Excuse" for prices going up. I like the idea of using a spare port in the top of the tank to monitor regardless of the type because of the lack of breaking the gravity fed fuel supply lines. No leaks...
 
 
Doing some searching...It appears that there are even some adjustable mechanical pressure sensors with a micro switch on top with a form C output. Looking into what might work.

oil tanks are not under pressure so I'm unsure as to a pressure sensor in the fill line would be adequate for what you are looking to do

Correct me if I'm wrong, but I believe that as long as the tube itself is sealed to the transducer, you are just measuring the pressure difference inside the tube as the volume changes.

That's the thought. The transducer at the top (sealed end) reads 0 PSI in open air. When you push the open end of the tube down in to the fluid pressure builds in the tube.

gatchel said:

That's the thought. The transducer at the top (sealed end) reads 0 PSI in open air. When you push the open end of the tube down in to the fluid pressure builds in the tube.

Click to expand...

 
Yes, that is how it works.  And it works very well, I have a lot of experience using these transducers, just not in heating oil.
 
EDIT: But heating oil is probably an ideal thing, since air will not dissolve into the heating oil.  Over a long period of time, air under pressure would dissolve into a water based fluid gradually reducing the pressure even if the fluid level stays unchanged, but to the best of my knowledge, air will not dissolve into heating oil.   These transducers are designed to measure the levels of water based fluids, but they assume that the tank is emptied frequently such that any dissolving of air into the fluid is too little to matter.

Read up on your hazardous area requirements.
 
You are playing with a dangerous scenario here by sticking a transducer of any sort intoa fuel oil tank.
 
This is not something to be taken lightly (think of those big chemical factory explosions - that is the result of getting it wrong here).

znelbok said:

Read up on your hazardous area requirements.
 
You are playing with a dangerous scenario here by sticking a transducer of any sort intoa fuel oil tank.
 
This is not something to be taken lightly (think of those big chemical factory explosions - that is the result of getting it wrong here).

Click to expand...

 
The transducer does not go into the heating oil.  That is what I meant by "no touch".
 
 
Heating oil isn't flammable in liquid state anyway.  It needs to be aerosolized or wicked.  It's not like gasoline.