Trident Acuracy after calibration

lilbitreefer · Jul 30, 2019

So I have had my trident up and running for about a week now. I noticed that my my alk was climbing started around 8.0 and was 8.4 by the end of the week. Thought I would do a calibration run through as it had been over a week since getting it. AFter the calibration the reading drops back down to 8.03-8.1. I got a bit curious and did a manual check with my Hanna checker and got 8.6. Any thoughts as to this huge discrepancy? Do I need to just let it run for a bit longer? I increased my dosing middle of last week as I was hoping to increase my alk to 8.5 and maintain it there. I don't know if I shouyld drop it back down because of the huge difference between readings. Thanks

jonmos75 · Jul 31, 2019

My Hanna dKH meter is always ~.5 different then the Trident Alk every time I compare the two. What this has shown me is how precise the Trident is.

If it was a full dKH then I would be worried about the difference, but .5 dKH I would not worry about the difference.

ca1ore · Jul 31, 2019

Seems to me there have been a lot of questions on this. With two data points that diverge, there's no way to reliably determine which is more accurate. In order to determine absolute accuracy, you'd need many more than two data points, across multiple testing methods/kits. My trident consistently measures anywhere from .5 to 1.0 dkh lower than my hanna. Whether it is 0.5 or 1.0 depends upon the age of the hanna reagent (older = 1.0). The trident does seem to drift out of calibration as you get closer to the end of the reagent batch - which is why it is important to recalibrate for each new batch. Yet, we don't know for sure that the calibratiosn solution is exactly that written on the bottle.

I've played around a bit with my CaRx, and the trident readings move as I would expect them to based on those changes; so I am comfortable that it is acceptably precise for my needs. Accuracy seems to be good enough also for our purposes. Just be careful about what you use trident to control. In my case, it's just sending alerts.

User1 · Aug 1, 2019

ca1ore said:
**** snip ****

which is why it is important to recalibrate for each new batch. Yet, we don't know for sure that the calibratiosn solution is exactly that written on the bottle.

This is my understanding as to why they include calibration fluid with each batch of new regents. However what I was wondering is why you say we don't know what the solution is. Note I do not own a trident but if the bottle says X, Y, Z then that is what should be in there otherwise how could they use it as a reference?

I've read a few people using the left over calibration fluid with the manual tests and it was the manual test kit that was wonky. No idea but was just wondering about the bottle comment.

ca1ore · Aug 1, 2019

I’m simply suggesting that if absolute accuracy is the goal, any ‘assumption’ is a risk. I have used leftover calibration solution in my hanna kits and the readings from the kits aren’t even close. Probably it is the kit that is off, but we don’t know for sure that the calibration solution is spot on accurate. As I’ve noted elsewhere, however, as long as it’s close enough that is good enough.

Silver14SS · Aug 2, 2019

ca1ore said:
I’m simply suggesting that if absolute accuracy is the goal, any ‘assumption’ is a risk. I have used leftover calibration solution in my hanna kits and the readings from the kits aren’t even close. Probably it is the kit that is off, but we don’t know for sure that the calibration solution is spot on accurate. As I’ve noted elsewhere, however, as long as it’s close enough that is good enough.

Agree completely, accuracy can only be evaluated with a known standard. I haven't seen a certified standard for our hobby, maybe one of the forum chemistry whizzes can share directions on how to make DIY Alk, Ca, and Mg standards? Anyone want to send their calibration fluid for an ICP test?

TM has a product, not sure if it's available in the US, and again there's the assumption it's correct.