Measurements differ from manual testing....

[wotnowires]

Hi,

I've recently setup my KH Director here, connected to my Profilux 4.

I seem to be seeing a difference of around .5 KH from my manual measurements with my Red Sea pro test kit....

I have taken the time to calibrate my pumps, and see exactly 100ml when manually dosing each pump.

My KH is at 8.4 according to my manual tests, but I am seeing anything from 7.9 to 8.1 on the KH Director.

I have validated that I am seeing no air bubbles.

What could be causing this difference?

Many thanks,
Paul.

[Gael]

All is ok.

http://forum.aquariumcomputer.com/sh...0033#post80033

http://forum.aquariumcomputer.com/sh...e-KHD-readings

[wotnowires]

Unfortunately I am not sure that I agree with this.

I have been slowy dosing my tank over the last 4 days. I have seen my kH rise from 7.6 to 9 using the RedSear Pro Titration method. At the same time, the kH director has gone from 7.6 (it was in line at first) to 8.1. It has shown 8.1 for the last day, despite the manual test showing a rise of nearly 0.5dKh. I have slowed my dosing, but I have real concerns over using the kH director right now as it appears to show no change when a manual test does.

Being out of line by a percentage is fine, but showing no difference when it should is more of a concern.

What could I look at to try to diagnose this further?

Many thanks,
Paul.

[Vinny]

Paul,

Recalibrate your KHD probe, then test again.

Also make sure your dosing heads are calibrated correctly and dispensing the correct amounts.

[WWIIIREEF]

Just for some more data. My kh director is reading 8.0, my hanna is reading 8.7, my red sea reads 8.4. Recently I bought a Lamotte test kit that matches the kh director perfectly. I've let loose the kh director to monitor and control my alkalinity. It has held my total alkalinity within +-.1 over the past several days. I have begun to dose a little more than I was previously when I mainly tested with my hanna dkh checker. Very happy with the results so far. Seems like most hanna checkers read .5 to 1 dkh higher than the kh director. I really like the Lamotte test kit as a backup/conformation test.

[WWIIIREEF]

When I dose more, the kh director definitely responds with higher readings. I calibrated the dosers and ph probe sevwral times. Including matching the ph solutions temperature to my tank, which is very close to the 25 celcius on the calibration fluids labels