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My redox reading can jump 5-20 points in seconds. Should the probe be replaced, cleaned? The tolerance is set at 5, it calibrates in 220 in less than 120 seconds and is about 1 year old.
If cleaning is required, what is the correct procedure. My instructions went AWOL.
Cleaning info can be found here
http://www.aquariumcomputer.com/Foru...ead.php?t=1606
they say probes don't last very long but mine became more stable when I added an earth pin to my tank (but it was measuring 30 /40 less when my T5's where on.)
Want to control nitrareductor filter with reedox, setting point -250.
Readings change constantly, reedox is about -150 always.
Now I can measure No3 in the aquarium as a result of bad controlling of the nitrareductor filter.
I changed the signal filter to 1, the same occurs.
What can I do to stable up the reading so it can control the filter in the area of -250 -200 that it should be operated?
Please advice.
.
how do the readings change? range? frequency?Quote:
Readings change constantly, reedox is about -150 always.
do the readings also change if the probe is immerged in glas of water?
It changes +-5 in a second.Quote:
Originally Posted by Matthias
I didn't test it in a glass of water, I can try if needed.
The probe is that of Aquamedic because it has o 13mm thread and it was calibrated in your fluids, calibration went well.
The same probe in another ORP controller, gives very stable readings.
I have one of your ORP probes, waiting to connect it to the expansion box.
Tell me what you want me to try.
can you see if setting the Operation Mode of the redox sensor to "Twooption controller" will fix your problem?
It was allready in 2potition controller.
have you tried changing it and setting it back?
Just did it, nothing changed.
A change of +/- 5 can be normal, it depends on several things, e.g. the flow.
If you incease the hysteresis the controlling should work without issues.
Where is the technical problem with it? Maybe I just don't understand.
The nitrareductor filter depends on low level of O2.
It needs to be operated in -250,
From the manual of Aquamedic nitratereductor:
"If it exceeds -50 mV, the denitrification reaction may stop at the nitrite stage!
If it falls below -300 mV, all the nitrate is reduced. The bacteria then start to use sulphate. This is a very undesired process because the end product of this reaction is Hydrogensulfide.
Hydrogensulfide (H2S) is toxic and smells very strange like fouling eggs."
I have set it to work, in area of -250.
So, in one sec it is above the next sec is bellow.
I changed the hysterisis so that powerbar is not allways in a on/off status.
But, when it goes to -260mV, it opens the flow of the filter, when the flow stops (pump connected to powerbar) I see readings of -150mV.
It should stop the flow of the filter earlier, but due to hysterisis and that values changes +-5 all the times, P3 stops the flow much later than I wanted.
My goal was to open on -250 and close on -230 and I can't do that (untill you help me :) ).
The hysteresis covers the range between the upper switching point to the lower switching point.
This means
if you have a set value of -250 and a hysteresis of 50 the upward control will be activated at -250 - (50/2) = -275, the downward control will be activated at -250 + (50/2) = -225, both controls (up and down) will be activated when the wished value is reached.
-> hysteresis must be large enough to reduce frequent switching (in your example due to the +/-5mV)
-> and must be small enough in order not to switch too late (in your example: -150mV)
if you want to open on -250mV and close on -230mV you need these settings:
nominal value -240mV (center of wished range), hysteresis 40mV (effective hysteresis for upward control = 40mV / 2 = 20mV)
if it does still switch too late:
Consider the time lag of your system (so-called "overshot"). Switching off will not immediately stop the raising of the redox!
O.K. Matthias, I just put the settings you told me, I will inform about the readings of mV (about the correct controlling of the nitratereductor).
PS: I just saw that when I put -240mV and press save, it saves the value -239mV, so I put -241mV and with save it went to -240mV. I do not know if this is critical or not, I just thought I should share it since it made me wonder why this happens (in possitive values, whatever I put, pressing save doesn't change it).