TDS meter calibration at the meeting

[EvilMel]

Hey guys, so I wanted to talk about the standards for our TDS meter calibration.

I can make them up but I was wondering about something. It says to calibrate them with NaCl, leading me to believe I should make up some solutions of say...1, 5, 10 ppm NaCl.

Is this what you guys want me to do?

1ppm, 5ppm, and 10ppm solutions? I don't see the point in going a whole TON higher. Maybe 5, 10, 20 would be better?

Let me know and I will make these up for us!

[Runner]

1ppm, 5ppm, and 10ppm would be ideal, I think. That is the area of the curve we are wanting to see, anyway. Nothing wrong with a slightly higher setup, but I'd before to see it down low since I regularly get readings of 4ppm to 9ppm on my present setup.

[Pandarian]

I think most calibration solutions are pretty high like the ~300-800ppm range. My meter recommends 342ppm. I'm just wondering if there would be any difference if we used 5/10ppm vs. something higher.

[EvilMel]

Well the reason we wanted to use really low standards is because the values we are measuring are so low.

It will not read accurate at all down in the <10 ppm range if you calibrate it at 300ppm. So we are going to calibrate them low in the hopes that they will read better in the lower range, ya know?

[Pandarian]

Yep, agreed. :rollface:

[philagothos]

Could we calibrate low and then check against a high concentration to see how much accuracy is lost due to calibrating at different levels? Just a thought.

[EvilMel]

Hi guys, ok so here's what I did:
The 1 ppm standard seems to be below the detection limit of the meter so that standard didn't work. I could never get it to read the 1 ppm solution no matter how far I cranked the screw on the back.

So I made five each of 5, 10, 20 ppm solutions for some people to take home and a single 100 ppm solution for us to mess around with at the meeting. I figure that not everyone needs the calibration solutions so we can just share the five amongst ourselves. For example, Art and I live 5 minutes apart so we don't need two sets of solutions so we will share one set. People who live close together can just share. If I need to make more solutions because someone desperately wants another set, then I can easily do that because I kept my stock solution and would only have to redo some dilutions.

OK? Everybody happy?

[imsqueak]

Thanks Mel. I have an unopened 800 ppm that came with my in-line tds. I'll bring it along if anyone wants to mess around with it and the 100 youre bringing. My thought is that it would be better to calibrate a 10 & 100 than a 100 & 800 but I happen to have this pouch sitting on my desk and I may as well let "someone" use it if they want to - I have no use for it as long as our helpful mad scientist is around.