VeeGee STX Calibration - what am I doing wrong?

[bknope]

I’ve had the VeeGee STX for about a week now. Using two different bottles of AquaCraft 35 PPT solution, I calibrate the VeeGee and use it a few times throughout the day.

The next day or later in the day, the VeeGee is no longer at 35 ppt (based on the reference solution) and is just a little below it.

Am I doing something wrong or missing a step?? I have a feeling it has something to do with the screw and calibration ring but I am at a loss

 

[andrewey]

Couple questions. After you calibrate the solution are you screwing down that screw? Also, how much is just a little? 34ppt, 34.5ppt, etc?

 

[bknope]

I do tighten the screw. I’m careful not to over tighten but tightening it does change the calibration slightly. I take this into account.

I would say next day it says it’s between 34.5 and 35, so maybe 34.75? It’s just baffling to me because I put it back in its pouch and don’t touch it. Am I not tightening enough?

 

[andrewey]

Hmmm- you don't need to tighten too much, so I'm going to assume you're doing it right. Have you let it sit for a few days or a week to see if it stabilizes at 34.75 or if it keeps dropping?

 

[bknope]

Hmmm- you don't need to tighten too much, so I'm going to assume you're doing it right. Have you let it sit for a few days or a week to see if it stabilizes at 34.75 or if it keeps dropping?

Good idea! I will try that the next few days. I have enough water prepared.

Just hoping I didn’t get a dud...