Tank Depth

All of the suggestions are good but one of the problems is that all of the drums are plastic, probably something I should have mentioned at the beginning. I have around 25 drums in the system. and would like to monitor each drum individually as well as a whole.

I came across these pressure sensors: the MPX2010 and its amplified version the MPX5010 in my rummaging through DigiKey. Has anyone had any experience with them? Do you think they would work in the harsh environment of a backyard in West Central Florida? What case styles would you suggest? Could I build them in a small potting box and pot them to make them more weather resistant and what sort of potting would I use?

John Larkin mentioned a bubbler earlier in this thread. All you'd have to do is to tap into the aerator system and meter a small amount of air into the dip tube. I'd think you'd want a small amount so that the pressure variations caused by larger bubbles separating wouldn't cause fluctuations in readings.

The pressure in the dip tube would equal the pressure of its depth and bleeding a tiny amount of air in makes up for leakage and dissolving air.

Hello James,

Argggh... coulda told us earlier.

... Forgiven.

With proportional pressure sensors that is going to become expensive. Unless money is not too important here I'd go with float switches.

Probably not. Also, note that only one of the 5010's is in stock, and they've got just 55 of them (seems you'd need 25 of these plus spares).

I'd look for something more industrial. Check Honeywell and the local Grainger outlet. Ideally I'd want something where I could drill a hole, cement in a fitting and then screw the sensor in with Teflon tape. IOW a clean plumbing job, no kludges. IIRC the Honeywell 236PC series has that thread but you'd have to check whether it fits, gives you the desired resolution etc.

Whatever you do keep in mind that stuff like this may have to be serviced and repaired. Murphy's law stipulates that there will be a driving rain, gale force winds and some hail when that happens.

But where is the fun in designing curcuits?

I was thinking just 2 to get on with the experimentation and then, when I have the bugs worked out, get more. I am not in a real hurry. Just something I thought about when I started to run sprinkler lines.

The lowest pressure rating that I saw was 15 PSI. Too high and I would have to construct some sort of amplifier to bring up the voltrages to reasonable levels. The pressure I believe that I would be working with is about 1.29 PSI (.43*3 Ft.). The range on the MPX5010 is 1.45 PSI and is amplified to have a F/S output of 4.475 VDC with a F/S span of 4.275 with a supply volyage of 4.75 VDC.

Then the irrigation pump shouldn't be running.

Maybe I should add a precipitation detector also?

___ How about a strain gauge that goes up to 400-500 lbs and weigh them? They are used in some pretty rough environments. I have no idea of the cost though. ___ If God hadn't intended us to eat animals, He wouldn't have made them out of MEAT! - John Cleese

Hello James,

True. But since you said you are in a hurry, wife breathing down your back, reminding you to get it done, saying there are lots more honey-dos on the list...

Sure, but there is fun in designing circuits :-)))

Yes, if you don't have a weather pattern like we do. A month of bone dry weather followed by a huge storm. Then another dry spell comes up, meantime a sensor croaked but now you have to leave for a lengthy biz trip to Asia.

I assume you run it via a sprinkler controller or something like that, with a master pump output. For many of those you can buy a precipitation sensor. The really good ones may allow for gradual adjustment of the zone times depending on how much precipitation there was.

Hello John,

Cool. Looks like the Lexus edition of ye olde float switch. Thanks for the link.

What wife? I ain't got no steenking wife.

Sure, but forcing a part to do what it wasn't designed for and not within the specs when there is one that is doesn't sounf good to me.

I'd like to take a trip to Asia on business. I'd like to have a business where I could afford to go to Asia.

Know of any ones like that?

Hello James,

Oh, I do that all the time. Thing is, the low pressure ones you mentioned look a bit flimsy. I'd prefer something that can be plumbed in.

Don't remember, have seen them at Home Depot. The Toro 12-station timer we have can be equipped with one so you could check their web site. I just didn't buy it because we really don't need that feature. Summers out here are nearly rainless.

Matbe I'll have to put thim in some sort of enclosure with pipe threads and pot them.

I'll have to look the next time I'm in the one up the road. I was there today but I didn't have those on my list. I'll start a new list.

Er, no. Continuous purge air would give erroneous readings. Purge, stop, wait a little, then measure. Using aerator air for purge trades a pump for a bit of tubing, purge valve is still required though, potentially a good deal.

Capacitive bridges aren't uncommon. Endress+Hauser has a range of them. Single teflon covered rod if the liquid is conductive, two rods side by side or concentric if it isn't. A bit of a hassle since they need to be calibrated in-situ. Largely superceded by ultrasonic and microwave systems.

- YD.

A float, a pot, a weight, a pulley, maybe some gearing. Take it up from there.

- YD.

Not if the purge valve is set so that the air flow is low enough. Then you can neglect the air friction just like you neglect the density of the air column.

Hello James,

Check the irrigation section at Home Depot. Usually just across the main aisle from where the timers are. You might, for example, use 1/2" nipples and then end caps to glue the sensor into via a precisely dilled hole. No idea whether the sensors are also PVC. If not it might not work. Then a larger end cap over the other could be used to protect the contact joints. Or just use one end cap, drill a hole for the wires and epoxy the sensor into the bottom of it. But then you'd need another kind of nipple and an end cap that has the thread on its outside.

In the end the whole thing would be screwed into the drums just like the water intake on many modern low-flow toilet tanks. A direct glue into the drum might be dicey because they can flex a bit.

Look for the term "rain sensor" on the package. Or take the timer out of the box and see if it has a rain sensor terminal pair. The sensor itself is probably going to be special order unless you live in an area that gets a good dose of thunderstorms in summer.

Bubblers are usually set up for one bubble every 3 to 10 seconds. Though I've seen plant operators, thinking the tank reading was low, open the needle valve full bore until they got the reading they wanted. The tank was actually low and the night shift woke me in the middle of the night to find out why they suddenly lost pulp dilution water. Getting off their asses and actually taking a look at the tank never crossed their simple little p*rn addled minds. Turned out some fool in the day shift had left the drain half open after some maintenance.

- YD.

Then you run the risk of never achieving purge, and not knowing it.

One bubble every minute or so should be sufficient to provide the proper purge.