Opinions on current Atlas Scientific hardware

[MaddyP]

Hmm, another result that suggests the issue is local to me. I will have to look for a local cause. Though as time goes on, it seems like the instability is decreasing. I also noticed that it took about 2 weeks for the constant creep higher in readings to moderate.

I also may be mistaking sensitivity for instability. I read the probes every 5 minutes and I noticed that when I get a jump of +/-100 uS from the previous reading, it seems to affect all the probes equally.

Hmm, more testing needed.

Certainly worth narrowing down equipment coming on/off since close electrical signals could be causing interference.

I’m reading the EC probe at 3 decimal places every 5 minutes and the graph is a straight line. No variation except for when I top off.

 

[Dennis Cartier]

Ok, so I have the 3 probes settled down (mostly). There is still a bit of a thermal swing of about 44 uS, but I am not too worried about it. This is just a proof of concept and I can worry about eliminating that along with a bit of noise in the readings when I use them in the build.

What I did was to make a manifold to hold the probes for in sump usage. It is just 3 tee's, end to end, with plugs. I have the plugs drilled for the EC probe dimension to allow the 2 mini probes to slide all the way in. I put an o-ring on the nipple and a press fit is tight enough to hold the manifold on the pump. I could have used a proper slip - threaded adapter, but I wanted to minimize length, and this was just a spur of the moment test.

Even though the end of the manifold is open, the pressure would pop the mini probes out of the holes. So I pushed an o-ring onto each probe after it was inserted in the plug and then used a small tool to tuck it down into the slot between the probe and the apron of the plug. The worked great and they are held in place really well now.

Having the small Sicce 0.5 pump flowing water constantly past the probes removed all the instability that I attribute to squatters and interlopers when they were bare in the sump. I was forever pulling them out to inspect and remove whatever had crawled into the electrode hole, but not anymore.

The only change I plan to make is to drill a couple of 1/4" holes in the final tee to allow the RTD sensors to be mounted in the water flow. I suspect that will help with the thermal swing.