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http://forum.aquariumcomputer.com/sh...-drifting-down
i read this topic and cross post also here...
GHL staff can you tell me if maybe also conductivity probe can suffer of interferences or miss calibration??
yesterday i re-calibrate again at show 34.5 (like a rifractometer perfect calibrated with FM-reference solution.
today nothing change in tank and sump and again 34.1 ... i bet that this evening i will read under 34 PSU.. why happen?
The accuracy of any probe is dependent on the precision of the calibration. The Conductivity readings are tied to the readings of your temperature probe. As such, as your temperature fluctuates throughout the day, the conductivity probe is also subject to change slightly.
Comparing the readings to a refractometer is only useful when you know that the temperature of the test fluid is the exact same temp as the tank temp. Otherwise, there will be a difference in readings from both measuring instruments.
I have the same issue, When I calibrate the probe, I used to introduce the plastic protector where I made the calibration into the sump for minimun 20 minutes in order to have the same temp at the temp probe than in the calibration solution. I have calibrate it like once per week, but it always show me a big different (from 1.016 to 1.021) and everytime I check whith a refractometre it is between 1.025 and 1.026, I have also tested the calibration fluid and it shows the correct amout so I don´t know exactly how to wrk with it, as the temp it´s not causing the fluctuacion.
any ideas?
I read somewhere about someone having similar issues and it was due to micro bubbles collecting underneath the probe. I hope this is the case as I will be reling on mine once installed!
Quote:
Originally Posted by JayHoe
Correct.
I used to have the same issues with my P3 and once micro bubbles were taken care off the probe was more steady and without downward swings
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I believe my issue is microbubbles as well. How did you eliminate them? I'm going to move the probe to directly in front of the inflow to see if the high flow will alleviate the bubbles.
Moving the probe to a lower flow area.
I also just purchased the cell GHL sells for probes. Waiting for my new build to install
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I have mine on the sump, previously I have it near the protein skimmer out take flow (vertex 150, just water flow), now I changed it yesterday to the first part, where the aquarium download flow is located (just opposite of the sock, and it´s imposssible to have microbubbles in those 2 positions but it works with the same values cycle
any more idea or sugestions?
Both locations are highly prone to microbubbles. I'd have a look at locating them in either lower flow areas, or active flow setup, such as a manifold, or better yet, the Measurement Cell GHL offers.Quote:
Originally Posted by thatanos
Yes - I agree to the microbubble theory :-) But can anybody explain, why in my case the IKS conductivity sensor is reading correct values (mounted in the same holder 2cm away) - with microbubbles?
The IKS module is ten years old!!! And works correctly from the beginning.
I assume, that it has something to do with the way the probe is build.
The IKS probe is mounted in a PVC fitting and the sensor plate is realy big (2x1cm). Also the sensor plate is mounted in a 45degrees angle to the pvc fitting. Above there are air holes (now I am knowing why there are "holes" :-) ). The fitting has a diameter of 4cm. I have never understood why - until now... If I put the sensor horizontaly/ parallel to the overflow - I have the same behavior like the PL4 with the IKS.
The bad thing ist, that this module can not be used with the IKS (because it´s the first generation without BNC coupler and with integrated circuit box).
In this moment, I am printing an comparable housing/ holder for my sensor including a bubble trap with my 3d printer.
Hope that helps. I have no more options in the sump to prevent micro bubbles.