ProfiLux 4 probes (temp, pH, salinity) accurate...?

[salty150]

Are the ProfiLux 4 probes (temp, pH, salinity) accurate...?

I know the Apex salinity probe is a pain to get to work right, etc.

Just wondering if the GHL probes work well...?

 

[Lasse]

IMO - they works well but as you mentioned - salinity probes are a challenge

There is a possible to set the offset on the temperature probe but it should be used with caution and if you are sure it is wrong. IMO - the real temperature its only interesting if you use any functions that are temperature depended like salinity probe below. I suspect that my temp may show a little to high temperature but I let i be.



The salinity probe can be tricky. I get mine to work well with some tricks. One of the is that it need a high flow through the gap of the lower part of the probe. I have placed mine just in my siphon pipe outlet in the sump. It needs to be cleaned rather often and - at least mine - have a small offset but that´s not much of a problem. My show 33.5 psu, my refractometer show 34 - 35 psu (difficult to read) and another electronical test shows 33.6 - but I get a steady reading. The upgoing trend is because I on my way to adjust to a higher salinity . goal 34 psu on my reading.

Worth to mention is that the calibration needs either to be done by the book or by using your own water as calibration fluid. The latest is tricky because you need to calculate the conductivity of your water with other methods and adjust it to the method GHL use. If you go by the book - the best would be - IMO - to use a very exact thermometer and adjust GHL´s temperature readings to that if you want a more exact reading (in absolute values) but if you can translate a little offset into real values in your head - do not touch the temp calibration. Most meters have an accuracy of ±1 degree C and you need one with accuracy around 0.1 (or lower) if there should be any meaning with adjusting your temp probe. I do not know the accuracy of GHL´s probe but in P4 its a digital and they use to have rather high accuracy

Because the temperature swings in the aquarium you need to use temperature adjusting by your Profilux temperature probe. My temperature swings from morning to night (by purpose) but my salinity readings are stable

As you understand - salinity measurements (or not even temperature measurement) are not an easy task - there is a lot of different way to do the conversion between mS (a conductivity probe gives the readings in mS = milli Sieverts) and we use PSU or specific gravity. The conductivity is also heavily depended of temperature as you understand.

But I have succeeded to have my salinity meter to work with an accuracy that let me have it to manage the adjusting of my salinity if it goes down. I know how I should use it if I want to use it for lowering the salinity too but for now have my sampling and skimate tend to lower the salinity

I have not worked with other systems salinity probe but with a little effort - I´m pleased with how GHL:s probe work

Hope this help you

Sincerely Lasse

 

[KStatefan]

I have never used anything else but I think they are decent. I added an offset for temp after measuring with a NIST thermometer.

Salinity seems to be stable but does not match my measurements. It can display three different readings PSU, mS or kg/L (which is not specific gravity). Getting salinity numbers to match with different measurement methods. The display on my P4 is normally about 1 PSU lower the calculating from my hydrometer reading.

If I was going to re plumb my setup I might look at using an measurement cell.

 

[Lasse]

If I was going to re plumb my setup I might look at using an measurement cell.

IMO - its a excellent solution - in my old work we use them with success. Because my siphon (around 2400 L/H) end 6 cm from a wall in my sump - I have placed them along the wall - direct in the flow - no need of a measure cell

Sincerely Lasse

 

[salty150]

Are there "better", more accurate options out there - that don't cost and arm and a leg, etc.?

I mean, none of them (the GHL or Neptune Apex, etc.) seem to work without having to play around with them, measure with something else and then do an offset in the software, etc.

 

[Lasse]

IME - if you want to still have arms and legs - I would say no. Especially if you want a central controller and online measurements.

Normally - you not need to adjust your temp controller - but if you use it for temperature compensation to the salinity probe - you maybe need to do it if you want it to have an accurate figure om the salinity measurements. But I can live with reading 33.6 PSU and knowing that it respond to around 34.6 on my refractometer. As long as I get a stable reading and not an erratic. Placed in the right place - GHL salinity probe give stable readings as you could see on my graph.

Sincerely Lasse

 

[ingchr1]

Any system you get will require periodic calibration of the probes.

When I was running a GHL sanity probe I found it be very stable. I no longer use it as I damaged the cable where it went into the BNC. Also, I don't have any use for a salinity probe in my system. One less thing to worry about keeping in calibration.

@Lasse can probably attest to this, but the pH probes seam to last for many years.

Temperature probe, I have never checked against anything else. No reason to believe it could be significantly out of calibration. If it were off by +/- 1F it wouldn't affect my tank one way or another.

 

[Lasse]

@Lasse can probably attest to this, but the pH probes seam to last for many years.

Yes - I have used many types of industrial pH-probes much more expensive than GHL:s pH probe - I always go back to the GHL probe. It is rather alike the old probe from Dupla - one that I found outstanding when I work in a Sewage plant 20 years ago. I have used GHL pH and redox probes in high loaded freshwater fish farms. Outstanding compared with others. The two I use now has been running in my aquaria for 6 years.

Sincerely Lasse

 

[BeanAnimal]

I would set it to PSU mode. I have not done the math in a while, but I don't think that GHL uses the standard equation of state for conversion.

I set to PSU and then adjust based on a tropic marin hydrometer. There is not enough adjustment, so I get it as close as I can. When my probe is adjusted as far as I can set it, it reads 34.4 when the TM is at 35

 

[Pod_01]

They work, I would not use any critical life support to run from them.
The salinity probe can swing, if things get between the probes.
Temperature is good, I tried 3 different devices got 3 different readings so I use the GHL one.
Ph probe will swing once in a while as well.
OPR looks good, not sure what to do with it.

I do clean all of them once a month and calibrated the salinity, pH and OPR twice in 6 years… So overall they are robust but as I mentioned I would not run anything critical like calcium reactor from them.

Here are general graphs:

Also I don’t dose any high pH two parts or kalk so that might explain the better performance.

Good luck,

 

[Lasse]

About the pH probe - at my old work we run several calcium reactors on them (and I think they still do) without any problems. Its - IMO - rock solid

When my probe is adjusted as far as I can set it, it reads 34.4 when the TM is at 35

That´s my experiences too - but I think it has with the temperature compensation to do . In your case - an incorrect reading of 6-7 degrees F can cause that deviation.

Sincerely Lasse

 

[BeanAnimal]

About the pH probe - at my old work we run several calcium reactors on them (and I think they still do) without any problems. Its - IMO - rock solid


That´s my experiences too - but I think it has with the temperature compensation to do . In your case - an incorrect reading of 6-7 degrees F can cause that deviation.

Sincerely Lasse

My system nominal is 77F

The temperature compensation documentation for the Profilux is ambiguous, so I am not sure exactly what it does. The 34.4 is close enough to my TM that I just use that number.

I too find that the probe must be in a high flow area and free of bubbles to be accurate.

 

[Pod_01]

at my old work we run several calcium reactors on them (and I think they still do) without any problems.

I suspect at workplace there will be procedures in place to maintain, clean etc… the probes.

At home I don’t think people have the same plan or drive hence I can see things going sideways.

I do believe the GHL equipment can drive Calcium reactor.

 

[salty150]

I guess what I don't understand is - Hanna and Milwaukee Instrument make a digital saltwater refractometer that is highly accurate.

Hanna even makes a saltwater testing "pen" which is highly accurate.

Yet no one can seem to make a monitoring probe that's accurate.

 

[Pod_01]

I guess what I don't understand is - Hanna and Milwaukee Instrument make a digital saltwater refractometer that is highly accurate.

Hanna even makes a saltwater testing "pen" which is highly accurate.

Yet no one can seem to make a monitoring probe that's accurate.

Problem is probes are in the salt water (harsh environment) all the time. Things will grow on them, corrode them, react with them etc… I suspect they can make better probes but the price of admission will be prohibitive.
Usually I find GHL probes accurate after cleaning and calibration, the problem is over time they drift…

All other devices are in and out or only a droop is required etc…

 

[Lasse]

I guess what I don't understand is - Hanna and Milwaukee Instrument make a digital saltwater refractometer that is highly accurate.

Hanna even makes a saltwater testing "pen" which is highly accurate.

Yet no one can seem to make a monitoring probe that's accurate.

I´m not sure on this

Spec of Milwaukee MA 887

Specifications​

• Range: 0 to 50 PSU: 0 to 150 ppt | 1.000 to 1.114 S.G. (20/20) | 0 to 80°C / 32 to 176°F
• Resolution: 1 PSU | 1 ppt | 0.001 S.G. (20/20) | 0.1°C / 0.1°F
• Accuracy: ±2 PSU | ±2 ppt | ±0.002 S.G. (20/20) | ±0.3°C / ±0.5°F

This mean that if I read 35 psu it could be all from 33 to 37 psu

Hanna´s have the same accuracy ±2 PSU

The Hanna salinity pen has an accuracy of ±1 PSU

None of these are better than the GHL probe I use for the moment. To measure salinity in sea water is not an easy task because of all different ions (and their percentage of the total amount).

I always check with at least two different methods and try to stay there. Today my salinity probe shows 34 psu and my refractometer around 34.5.

As @Pod_01 mentioned - cleaning of the probe is important. My probe needs a overhaul with a soft toothbrush every third or fourth day

Sincerely Lasse

 

[BeanAnimal]

I guess what I don't understand is - Hanna and Milwaukee Instrument make a digital saltwater refractometer that is highly accurate.

Hanna even makes a saltwater testing "pen" which is highly accurate.

Yet no one can seem to make a monitoring probe that's accurate.

Except none of the devices that you mentioned are accurate or repeatable. You can calibrate your conductivity electrode against a Tropic Marin Hydrometer and use the hydrometer as the reference standard.