Ph at 9.14 using Ph1 sensor mystery

[TonyRB]

Hi all

I have a strange problem with my with my Profilux II plus.

Basically i set the 4 year old computer up on my new system around 4 months ago, previous to this the computer ran fine for years.
The Profilux has an extra Ph card in it also.

No matter which of my older probes i used in Ph 1 (on the PCB) the tank Ph would read around 8.9-9.1, both probes calibrated correctly and either would read correctly when calibrated on Ph 2(add in card).

After some time i decided to buy a new main board and display board as mine had faded, i also purchased a new GHL probe and fluids at the same time.

Fitted the boards and calibrated the probe. Ph 1 still measured 9 after basically renewing the internals of the computer and probe.

The calibration data of Ph1 reads Value 1 /Ph 7 = ADC 1 408 Value 2 /Ph 9 = ADC 2 204
Ph 2 reads Value 1 / Ph 7 = ADC 1 480 Value 2 /Ph 9 = ADC 2 234

Looking at the calibration data both probes look to be within spec and calibrating fine. Either probe when calibrated to Ph 2 reads a correct Ph that one would expect for the tank i.e 8-8.2 depending on time of day.

Ph 1 always reads high.

My next step was to remove a water sample in a glass and measure with the probe on Ph 1 away from the tank , the Ph magically dropped to 8.2

So now i checked for stray voltage, this was 7 volts and the Ph probe started to behave correctly when i switched off my new Deltec E-Flow AC sine wave return pump and also my UV as this had a small effect.

I then installed a titanium ground probe to the water, this dropped the Ph 1 from 9.19 to 8.68 , better but not correct, after this no residual voltage could be measured in tank but the Deltec pump still upset the Ph 1 probe.When turned off the Ph dropped correctly.

I then swapped out the E-Flow pump, this had now started to become expensive as the pump is fabulous quaility and the new boards and probe price in addition. The new pump upset the PH 1 port in the exact same way.

Ph 2 continued to measure correct tank Ph which leads me to believe that Ph 1 has a degree of extra sensitivity and there is nothing wrong with my pumps or Ph 1 but it still leaves me with a high Ph 1 measurement i need to resolve.

Any thoughts?

regards and thanks for your help

P.S sorry for the long winded post but i wanted to be complete.

[Yaragos]

Hmm, that motor has variable speed.
Its basically a VFD.

Two common ways to slow down a motor.

1) By lowering the voltage, but you risk burning the motor, due to high currents.
2) By changing the hertz (PWM), decreasing the cycle time will slow the motor down, with the current also going down with it.

Problems with PWM, it can generate tons of noise, if not done properly.
You may want to talk to the manufacture about there design, just a thought.

[TonyRB]

Hi
Many thanks for the response.

Im going to enquire about pump noise etc so I'll look at that aspect although the pump runs on a true or pure sine wave inverter so should be excellent with regards to noise.

Im still a little confused as to why Ph2 seems oblivious to any noise though while Ph1 goes high, both are connected to the same computer after all.

Regards Tony

[Matthias]

I have an idea about the pH miracle

the pH-input circuits were improved over the years so they got immune against (most) electrical noise

you say your ProfiLux is 4 years old, that could mean that this is an older input bute the PLM-pH has a new input

[TonyRB]

Hi Matthius

Thanks for the response, yes the computer was 4 years old which is why I replaced the main board and display last week basically giving me a new computer again. So are we saying the P2 plus boards are all old design with the PLM not updated on the newer boards and I've basically wasted my money?

Best wishes Tony

[Matthias]

send me a picture of the rear board and I can tell you the version of the board

"waste of money" - I don't know what the reason was for the replacements so I can' judge

[TonyRB]

I will get a picture Matthius.

Please read the thread, I purchased the rear board because of the high Ph error that reads from the on board Ph. The plug in PLM boards is fine and reads the correct Ph.This is why it's wasted money, I replaced the main board , the front dim screen , a new probe and solutions but kept the old plm-ph add in board as it was fine.

The Ph1 on the main boards still reads high so I haven't achieved anything by replacing the main board ( back boards) and probe.

Best regards

[TonyRB]

Hi

Pictures of the new main board and the older Ph add in card.

291029112912

many thanks Tony

[TonyRB]

Hi all

Calibrated all probes again tonight and installed an Aquamedic Ph controller as a secondary check,here are the results from the tank:

PLM add in Ph card( original and a 2007 made card I believe) = 8.12ph
Aquamedic Ph controller freshly calibrated = 8.08 ph
New Profilux 2 plus main board Ph port = 8.69 ph

The Plm card and Aquamedic read the same if in the tank or in a glass of tank water. The on board drops to 8.2 when in a glass of tank water.

Any ideas?
The only other option would to be to buy another add in Ph card and turn the on board off but the mystery remains.

Many thanks for any help Tony

[Matthias]

ok, you have a V1.07 rear board which has already a galvanic isolated input (you can see the DC/DC converter in the pic)

I assume your PLM-pH is version 1.02, is this right?

if this is the case the both pH-input circuits are exactly the same

did you swap the probes for a test?

has ProfiLux a grounded PSU?

[TonyRB]

Hi Matthius

Many thanks for your rapid response.

Im not sure on the PLM-PH version, is there a way to find out, i do know that i purchased it back in 2007 i think.It was one of the first in the U.K

Youve lost me on the galvanic isolated input, it sounds good though and something i should have in my life.:)

I have swapped the probes previously but i'll do it again tonight to double,double check.

The PSU is one of the old units with the double insulation rather than an eathed PSU, do you think this might cause problems?

All the best Tony

[Matthias]

the version is printed on the PCB

grounded PSU - may help, but I am not sure since one input works and the other not

[TonyRB]

Hi again, the mystery deepens unfortunately

The PLM-Ph card is v1.00

Ok I swapped the new probe to Ph1 and calibrated.
I sat the probe in aquarium water in a glass it read 8.16
I sat the probe in tank and it read 8.44, better but still high.

At this point I turned off the pump and it dropped to 8.16

I then calibrated the older probe on the PLM-Ph card

Probe in glass of tank water 8.18
Probe In tank 8.18
Pump off 8.18

Now here is when things get odd.

I then tried to eliminate other components.
I unplugged the temp probe, no change
I unplugged the data cable to the digital plug bars in S1-S4 and the Ph on Ph1 dropped from 8.44 to 8.25 this was repeatable.

Next I unplugged the data cable at the plugbar, the Ph stayed at 8.44.

With the RS data cable still unplugged at the plug bar I unplugged from S1-S4 again the Ph dropped .

So it would seem the cable is picking up noise like an antenna but there is still some interference that requires the return pump to be switched off for the Ph to read correctly.With the pump turned off unplugging the S1-S4 didn't achieve anything as the Ph had dropped to correct levels.

So it would seem Ph 1 on the board is sensitive to a form of magnetic interference that's in the tank and the PLM module acts like there is no interference at all, odd yes.

So I'm closer but kind of further away, I can only assume this. is a freak phenomenon but would like to know of any shielding or insulation the PLM may have over the on board Ph as it may give me a better clue how to fix this.

Thanks for all your help Matthius, much appreciated.

Do I win this years oddest post award? Nothing is simple in reef keeping it would seem lol.

Best wishes Tony

[Matthias]

now I have at least an explanation for the different behaviour of PLM and ProfiLux

your card version 1.00 has a very strong hardware filter which eliminates nearly all electromagnetic noise - also from "very bad" electric devices

we made this filter later the half because some customers complained that the card reacts too slowly on pH-changes which is especially a problem with refillable glass pH-electrodes during calibration

but the new (current) filter - which is on your ProfiLux - is strong enough too eliminate normal electromagnetic disturbances - and fast enought at the same time for glass sensors

I see only one solution: try to get rid off the electromagnetic noise - is the pump grounded?

[TonyRB]

Hi Matthias

Thanks again for the reply.

I dont think there is anything badly wrong with the pump as neither the PLM-PH or the Aquamedic controller shows any sign of being upset by the pump. Equally the pump is a very well made piece of German equipment as is the GHL so dont think there is any real problem with either.

The mains cable is wired directly into the controller of the pump and its a 3 core by the looks of it so almost certain its earthed.

I think ill just turn the on board Ph off and possibly get another PLM-Ph card as this is one of those faults with no specific cause so will just have to live with it.

All the very best Tony