Erratic EC reading from Bluelab Guardian
- Thread starter mobutu202
- Start date
Did a water change and EC meter started bouncing around like this. 24 hour history shows min 1.0 max 1.4 but last week I had a very consistent flat line around 1.2 and I used the same recipe. Owners manual said check for a bubble which you can seething i did there around 1600. It got better temporarily. Should I clean the sensor?
Wastei
Well-Known Member
You did a reservoir change and wonder why the sensor value dipped and later raised and stabilizes?
The sensor is doing what it's supposed to do showing actual EC reading and that fluctuates after a reservoir change. It takes a while for all the different salts to fully dissolve and settle. Even topping off with water it may show fluctuations.
Cheers!
No I'm wondering why the line looks like a lie detector when it used to be flat
Wastei
Well-Known Member
I tried to explain that in my earlier post.
You hardly ever need to clean or calibrate an EC probe. They typically last decades.
That's the thing. It hasn't stabilized. It's getting more unstable! I'll post a screenshot
My ec truncheon doesn't live in nutrient but I need to clean it every circa 6wks, there's a film builds on the probes and it loses sensitivity.
A spot of jif/cif cleaner works well, put a drop on the probes and give them a light rub with cotton bud.
This sounds extreme, no it is extreme but recommended by Bluelab themselves, if you can't get a stable reading use fine emery/wet n dry and give the probes a rub then clean them.
A spot of jif/cif cleaner works well, put a drop on the probes and give them a light rub with cotton bud.
This sounds extreme, no it is extreme but recommended by Bluelab themselves, if you can't get a stable reading use fine emery/wet n dry and give the probes a rub then clean them.
You've got a very detailed trace of the electrical conductivity of your nutrient solution because the electrical conductivity of the solution is constantly changing.
If the granularity of the display was, say, 0.1 units, it would be a fairly smooth line but the trace in the screenshot is sufficiently detailed so that the line is jagged.
EC changes constantly because a plant is constantly exchanging chemicals. As chemicals are exchanged, the electrical conductivity of the solution will change. We growers use EC to indicate the "chemical strength" of a nutrient solution but that's a complete fallacy.
EC does not tell you what nutrients are in the res. It's called electrical conductivity because it's measuring the electrical conductivity. The only way to know what chemicals are in the res is to do chemical analysis of the nutrient solution.
Why doesn't it tell you what's in the res?
The chemicals that are taken up quickly have very little impact on the electrical conductivity of the solution. In contrast, the chemicals that are taken up more slowly have a larger impact on electrical conductivity.
Chemicals start leaving the nutrient solution in the res within minutes of you putting in a new res and, within a matter of hours, N, P, K, and Mg have been taken up out of solution (in a small res). Despite that, the EC may not change at all. It's only when the chemicals that are absorbed more slowly, Ca being on of them, that EC will increase.
On the other hand, if you introduce a lot of nitrogen as ammonium, pH will drop very quickly, even in a very large res (my res holds 28 gallons and I tried a "bloom booster" (unneeded in hydro) and pH dropped like a rock.
Why are you using an EC meter?
Re. EC "bouncing around". We use water soluble chemicals that go into solution very rapidly. Drop a probe in a bucket of nute solution and it will flat line.
Bluelab sells a "growers tool kit" that includes a small tooth brush and a very slightly abrasive paste. When I calibrate my EC and pH meters (the light flashes every thirty days), I use the brush on both the EC probe and the pH probe. I'd stay away from something abrasive like emery board/paper and just go with an old toothbrush.
You can mix up conductivity solutions with table salt to a know ec, 1g/ltr give 1.0ec iirc if for calibration /testing
It's only to be done if you can't get a stable reading, I'd cleaned my probe and couldn't get a stable reading and that's what Bluelab instructed me to do and it'd worked fine since.
I've attached the manual for my monitor. Section 10.1 says to clean the EC probe when calibrating pH.
I have their EC pen, pH pen, monitor, and doser and I've gotten into the habit of using the brush each time I calibrate.
Re DIY - not a bad idea. I've had the same bottle for forever but it wasn't cheap so I might DIY next time. Good idea.
Looking at the trace now I realize I only saw that falling line, not that the EC was approaching 0. It would have taken a very long time to drive EC that low.
Good to see that the resolution was to clean the EC probe but, also, pH increased and is now flat.
I have ended up replacing the pH probe about every 18 months. The EC probe isn't replaceable, on the version I'm using, at least.
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