Waterlevel ATO needs barometric differential

Expansion modules and attachments
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KRavEN
Posts: 104
Joined: Sun Mar 17, 2013 8:21 am

Waterlevel ATO needs barometric differential

Post by KRavEN »

I've been running the 4 port waterlevel ATO for a while now and I've noticed that my level goes up or down depending on the barometric pressure. If I had last calibrated while we had a high pressure system in my area and then a storm comes through the difference can be a couple inches. This makes sense because the expansion is really just 4 pressure sensors.

I don't use all the ports on my expansion so I was thinking that the high level could be computed as the difference between an unconnected port and the 100% level that is set on a port during calibration.

For those that use all 4 ports I was thinking I could work up a webservice that returns the barometric pressure for a specific zip code and then add a periodic call to that service to the RA code.

Anyone else noticing the same thing or have any thoughts or suggestions?
rimai
Posts: 12881
Joined: Fri Mar 18, 2011 6:47 pm

Re: Waterlevel ATO needs barometric differential

Post by rimai »

I'm in CA, so I'm not sure if we have that much pressure difference, but I've been using mine to throttle my DC return pump and create a bubble free and noise free system for quite a while. It think it's been almost 1 year already.
My tolerances are pretty tight. I have about 3", if I'm not mistaken, of travel in my overflow chamber, which means from 0 to 100%, water only travels 3". If water is too low, air gets sucked in and if too high, it hits the emergency float switch. I've never had to recalibrate it yet.
Roberto.
KRavEN
Posts: 104
Joined: Sun Mar 17, 2013 8:21 am

Re: Waterlevel ATO needs barometric differential

Post by KRavEN »

I'm in Dallas, we get huge low pressure systems and thunderstorms and the barometric pressure can swing quite a bit. I originally though maybe I was getting bubbles in the tube causing the pressure to rise so I hooked up 2 tubes in different areas of my sump and they both track within 1-2% of each other so I don't think that's the issue.
rimai
Posts: 12881
Joined: Fri Mar 18, 2011 6:47 pm

Re: Waterlevel ATO needs barometric differential

Post by rimai »

Did you get measurements of the unused ports overtime?
I'd load them in a custom variable and use the chart to plot a graph overtime and see if the sensor is sensitive enough to measure air pressure difference.
The other thing I can think of would be air expansion, but I doubt it would interfere that much.
Roberto.
sabo
Posts: 129
Joined: Tue Sep 24, 2013 3:18 am

Re: Waterlevel ATO needs barometric differential

Post by sabo »

Your right thinking this, but after doing the sums I don't think you should get so much of a swing. Let's see if my maths is right.

One atmosphere is a fathom.
One fathom is 6 feet of water.
Six feet of water is 1800mm
One atmosphere is 1013hpa
So 1.77 mm of water difference per hpa.
For 50mm of water difference you need 28hpa front/ storm to come through.

Now I think about it, with some of the wild storms you guys get in some parts of the states, it wouldn't surprise me at all.
sabo
Posts: 129
Joined: Tue Sep 24, 2013 3:18 am

Re: Waterlevel ATO needs barometric differential

Post by sabo »

Actually, I think my memory sucks. I thought a fathom was an atmosphere, but I think that's wrong. But I'm on my phone at the pub, so this will have to wait. ;)
KRavEN
Posts: 104
Joined: Sun Mar 17, 2013 8:21 am

Re: Waterlevel ATO needs barometric differential

Post by KRavEN »

Well, WL port 4 has never been hooked to anything so if I could isolate that on the portal web chart I can see the swings.
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