You know what you might be able to do is to get your hands on a natural gas flow meter. They work at the low pressures ( inches of water pressure) encountered with fuel gas systems. If you could find a used one, you could monitor the flow directly and be pretty safe about it. But, The OP's country, State, County would have regs concerning the issue and they should be consulted before proceeding. A camera watching a currently installed meter would pretty much be a slam dunk as there would be no modifications to the system at all. The problem here is the resolution would be pretty low and if you were looking for a daily or even weekly flow rate data, it is not going to happen by watching the liquid level in a 500 gallon tank. Your going to have to install some kind of gas phase flow meter.
I see that the Hall effect gauges that are on most propane tanks just need the monitor cable and
from there we would be able to build an arduino or Rasp Pi config to monitor this..
most of the other sensors I see are inexpensive but the R3Dones that go on the tanks seem
to be under lock and key by many of the manufacturers.
Rochester says they only sell to "remote monitor OEMS"
http://www.rochestergauges.com/products/R3D.html
has anyone found a source for the remote monitor cable and sensor?
I am going off the beaten path here.
your heater gets a signal from the thermostat when it is calling for heat.
your gas valve opens and the flow starts, a thermocouple is needed with a pilot, or you have an pilot-less and start the fire each time.
once the heat exchanger/combustion chamber starts to get hot, the fan starts.
your arduino should be able to tell when the heat is on. a rise in the heat exchange. temperature sensors galore ! for the Arduino.
you can monitor that hte fan is on. lots of ways to do that as well.
log your run time. after X hours, go look at the tank.
each time you fill, note how many hours run time you had.
no need to actually see what the tank level is for most of the information.
as for getting a sense of full, after a few fills, you should have a good feel for calibrating the hours to usage rate.
my oil burner has a motor on the oil burner itself. I know that an hour dumps X gallons of oil.
the heat exchanger fan is not 1:1 with the burner motor. not sure if you can monitor the gas valve.
a simple 10 point LED fuel gauge can be mounted on your Arduino to show what it thinks is the tank level.
the real goal, might be to know once you are less than half full ?
and doing all this should be a simple and fun exercise.
Sounds like a fun project.
Initially I'm trying to put something together that would notify the level of the propane tank when it goes under 30% or so.
got a relative that can't get out to check the tank and I can't drive to check it for them.
the tankutility device kinda already does it.. but they want 200$ for a Hall effect sensor and some simple programming.
figured I would try this first.
finding the correct sensor is the first thing.. it is already made.. but sounds like Rochester is holding it under lock and key
in the mean time, google degree days and put in your nearest area.
get the spreadsheet for the last 3-4 months and get copies of your gas bills.
I find that using 65 degrees, and a gas boiler, in NYC, that gas uses is close to 75% of the total of degree days.
100 degree days = 75 gallons of oil
the use is on a curve, so it is not linear, but I am usually near 10% of true. the colder it gets the lower the percentage.
since I just use it to figure fills and schedule when it calculates to half, I am good.
if you want this remote, then all the extra fun of internet comes into play.
pert:
The forum screwed up the URL. Here it is fixed:
https://www.youtube.com/watch?v=EfB_MaIB_Tk
However, I think you posted the wrong link because that's just an explanation of how you need to thump the gauge to get a good reading (I guess some part of the system can be a little sticky). So that might be something to consider for this project anyway.
in my old pneumatic controls days, the spec sheet said that pressure gauge was within 2% after rapping.
I bet if I searched the Marsh Gauge site I could find that technical bulletin on how to rap a gauge.
and yes, in the HVAC world it is spelled gauge, not gage.
mastiff:
got a relative that can't get out to check the tank and I can't drive to check it for them.
Propane companies do offer a service where they will keep the tank topped up. I'd guess they try to estimate when they need to come out based on past use so they don't make any more trips than necessary. It is an extra fee so over time would probably end up costing more than the sensor or whole system.
Of course that takes the fun out of the project but it's worth considering all the available options.
The gas nozzle should deliver a fixed mass of gas per unit time .... Kg/Hr or pounds per hour. If you could find that specification, then integrating the gas valve open time would give a reasonably accurate consumption.
A Rochester gauge is shown on Amazon though listed as unavailable. It suggests Rochester did not always limit sales to OEMs. If you search around you may find a supplier.
This site seems to sell them for $15
CharlesDavis:
The gas nozzle should deliver a fixed mass of gas per unit time .... Kg/Hr or pounds per hour. If you could find that specification, then integrating the gas valve open time would give a reasonably accurate consumption.
My oil burner has an orifice and creates pressure. the orifice is listed at gallons per hour at x pressure. I believe that a gas furnace works in the same way.
what I did was to run the data logger.
when I got a fill, the receipt had time and day.
on the next fill, I just too, the spreadsheet from my data logger and totaled the run time.
simple math at that point and the data is a few percent off from actual. and that might be dependent on the guy filling the tank. one guy can put in 5 gallons more or less than the next.
Not looking for the gauge. I have that.
Looking to get the actual hall effect sensor that snaps into the gauge.
all the utilities are using them, tankutility.com also uses them.
they just want 200$ .
It would probably cost 6$ for the sensor and a couple resistors and I can connect it to an Arduino and have it notify me or when less than a certain percent. or graph the tank level.. etc...
mastiff:
Not looking for the gauge. I have that.
Looking to get the actual hall effect sensor that snaps into the gauge.
all the utilities are using them, tankutility.com also uses them.
they just want 200$ .
It would probably cost 6$ for the sensor and a couple resistors and I can connect it to an Arduino and have it notify me or when less than a certain percent. or graph the tank level.. etc...
TankUtility sells a "WiFi Enabled Propane Tank Monitor" for about $200, but it also looks like they sell "dial replacements" for $15. See the link in post #48 and this one;
I don't know what exactly they mean by 'dial' but the part numbers in the pdf look like Rochester gauge numbers. It could be a 'dial' is the gauge with the hall sensor.
It also looks like they sell "Dial replacement
Yup.. have been looking at tankutility for a while..
All they did was make a sensor connect to a mini computer so it would check the tank level.
Didn't want to waste 200$ when the sensor has to be only a few dollars. and I can connect it to the existing Pi that I have.
You are not reading the post, they sell dials for $15.
Whether or not the dial has a sensor is not clear.
I apologize.
I did read the post. I know dial doesn't have the sensor in it. I thought that was already a given.
The sensor snaps into the goove on the top of the gauge
The gauge just lets you connect a sensor to the top that passes through to the magnet that is currently
running the tank level on the gauge.
This link shows the gauge and the sensor cable although the cable doesn't seem to be available anywhere.
http://www.rochestergauges.com/products/R3D.html
I am aware that there are some devices and already made for this.
and even some propane companies use these types of monitors already.
So the sensor cables are out there and being used. Just need to find the cable.
It can't be that expensive. I hope 
I went to this website;
http://www.bergquistinc.com/
I searched for Rochester and it did come up with some dials "with remote sender" which I take to mean the sensor. No prices though.
Hello all. I have been looking for a solution to this same "problem" for my folks who are now heated by tanked propane. I'm curious if anyone has made progress in the last 8 months.
My folks have a "Remote Ready" gauge made by Taylor Products. When I was looking for remote monitoring options, I noticed the gauge pictured here is 100% identical and the ad specifies the LevelCon (the product this company sells) fits both Rochester and Taylor gauges.
I did some more Googling and discovered you can buy the Squibb/Taylor sensor for about $80 which is steep, but 30-50% of other monitors - and it gets me closer to having the data in a database/home brew web-UI vs elsewhere/nowhere.
I also found a place south of Seattle, WA that sells the extension cable - maybe they could sell me a sensor, too. I think I need to make some calls on Tuesday.
https://www.northwesttankparts.com/product-p/136105-bq.htm
I am going to do some more research into if the companies will sell me the Hall Effect sensor. If so, then I have to decide how to handle the wiring. The tank is about 20ft from a wall outlet, and a location where I will have another two monitoring devices (outdoor temp and water level). Do I extend and sheath the wires back to the shed, and use a single Arduino for the three tasks? This seems the most straight forward to me.
I will post any updates I have regarding the sensors in the future.
E: Added URL tags, I figured the forum automagically did that. My bad!
The standard cable is only 6' long so the question really is can that be extended to 20' with the signal still being readable - why not ask the supplier?
You might want to think about lightning, a buried cable might be best.
At face value a single Arduino could easily monitor the three signals unless it also has something complex to do.
Here is a datasheet for the R3D
http://www.rochestergauges.com/products/R3D.html
the sheet states;
-
Operational Voltage Range
-
3.5 to 6.0 vdc/ratiometric.
-
Output Voltage
-
Ratiometric 5-80% of input voltage @ 5-80% volume.
There seem to be only three connections; power in, ground, output.
I guess if the 20' cable has low resistance the meter could be read but somebody with electronics knowledge needs to confirm that.
The meter is only accurate to +/- 4% of full scale and that excludes float errors which could well be the major error. I think the guage will give a good indication if the tank needs filled but it will not give an accurate reading of the volume of propane delivered.
I have been looking into this on and off again for a couple of years.
The gauges seem very easy to find and I have one of my tank. The sensor cable with the wire seems to be very rare and the ones that are already connected to something or expensive.
I found this video tonight and the company that posted it claims to be willing to sell the sensors.
I contacted sales at DPStele. Com. I will post here if I actually get a hold of one of these sensors.