Measurement Cell in the Wild
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It would be to much a pain to plumb in on my tank. Also not sure about the fitting size For piping. Also those are the same type fittings for the probes as the KH Director, they could leak... (smirk) I’ll just keep the probes where they are at In the sump.
OP
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esther
Valuable Member
Where do you have them in your sump? I feel like I'm having to calibrate the salinity probe more often than I would like. Trying to reduce that.
My probes are in the compartment after my filter socks. This would be a refugium section In most sumps. This is also the section just prior to my heaters. So it’s the coolest water running across the probes before getting heated.
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esther
Valuable Member
Maybe I’ll move them there for a couple of weeks and see what happens. Thanks!
A GHL salinity probe measure conductivity and it is rather difficult to both calibrate and run in a saltwater tank. They are very sensitive for temperature. This is not only a problem with GHL:s probes - it is valid for all type of salinity probes build on conductivity. It's important to do the calibration exactly right and at a known temperature.
After the calibration is done - one very common problems is that the probe maybe show 34 psu in the start and after that - slowly going down with time. You touch the probe or clean it and it goes back to your 34 but start to decline again. This type of behavior is IMO connected to the flow around the probe. It must be placed in a rather high flow - if you do that - this down going trends will be gone.
When all things calibrated in the right way, the probe is situated at the right place - many probes have an offset - it means that if the right value is 35 psu - the probe show 33 psu. Why it is this way - I do not realy know - there is a lot of factors to consider like stray voltage, interference from other electrical equipment, types of ions in your aquarium and many more factors. Compare with a calibrated refractometer and translate in your head when you read the values is one thing to handle this. it works if the probe give a stable reading (plus minus 0.2 psu) Another is to use the manual temperature tab. Do a salinity test that you relay on (a good, calibrated refractometer is one option). When you have a stable reading on your probe - adjust the manual temperature in a way that give you a reading similar to the refractometer. This works if you have a stable temperature in your aquarium.
You ask yourself - How can they sell something so complicated - the truth is that it is very difficult to measure salinity even for a professional with rather high prized equipment. However - IMO - the GHL equipment give (with right calibration and right placement) a stable reading and you can see the trends in your aquarium - if it going up or down
Sincerely Lasse
After the calibration is done - one very common problems is that the probe maybe show 34 psu in the start and after that - slowly going down with time. You touch the probe or clean it and it goes back to your 34 but start to decline again. This type of behavior is IMO connected to the flow around the probe. It must be placed in a rather high flow - if you do that - this down going trends will be gone.
When all things calibrated in the right way, the probe is situated at the right place - many probes have an offset - it means that if the right value is 35 psu - the probe show 33 psu. Why it is this way - I do not realy know - there is a lot of factors to consider like stray voltage, interference from other electrical equipment, types of ions in your aquarium and many more factors. Compare with a calibrated refractometer and translate in your head when you read the values is one thing to handle this. it works if the probe give a stable reading (plus minus 0.2 psu) Another is to use the manual temperature tab. Do a salinity test that you relay on (a good, calibrated refractometer is one option). When you have a stable reading on your probe - adjust the manual temperature in a way that give you a reading similar to the refractometer. This works if you have a stable temperature in your aquarium.
You ask yourself - How can they sell something so complicated - the truth is that it is very difficult to measure salinity even for a professional with rather high prized equipment. However - IMO - the GHL equipment give (with right calibration and right placement) a stable reading and you can see the trends in your aquarium - if it going up or down
OP
OP
esther
Valuable Member
A GHL salinity probe measure conductivity and it is rather difficult to both calibrate and run in a saltwater tank. They are very sensitive for temperature. This is not only a problem with GHL:s probes - it is valid for all type of salinity probes build on conductivity. It's important to do the calibration exactly right and at a known temperature.
After the calibration is done - one very common problems is that the probe maybe show 34 psu in the start and after that - slowly going down with time. You touch the probe or clean it and it goes back to your 34 but start to decline again. This type of behavior is IMO connected to the flow around the probe. It must be placed in a rather high flow - if you do that - this down going trends will be gone.
When all things calibrated in the right way, the probe is situated at the right place - many probes have an offset - it means that if the right value is 35 psu - the probe show 33 psu. Why it is this way - I do not realy know - there is a lot of factors to consider like stray voltage, interference from other electrical equipment, types of ions in your aquarium and many more factors. Compare with a calibrated refractometer and translate in your head when you read the values is one thing to handle this. it works if the probe give a stable reading (plus minus 0.2 psu) Another is to use the manual temperature tab. Do a salinity test that you relay on (a good, calibrated refractometer is one option). When you have a stable reading on your probe - adjust the manual temperature in a way that give you a reading similar to the refractometer. This works if you have a stable temperature in your aquarium.
You ask yourself - How can they sell something so complicated - the truth is that it is very difficult to measure salinity even for a professional with rather high prized equipment. However - IMO - the GHL equipment give (with right calibration and right placement) a stable reading and you can see the trends in your aquarium - if it going up or down
Sincerely Lasse
Thank you for the torough response, @Lasse. Much appreciated!
Michael Gray
Valuable Member
Mine is all over. I just look for a range. And use my refractometer. To confirm it's still 35. My probe never reads 35 not close. Like 33 to 34 tops
Regarding Conductivity, one thing that threw me off for a while is that DENSITY is different from SPECIFIC GRAVITY. We, in the U.S. at least, generally prefer S.G. but the Profilux only offers Density, Conductivity and Salinity options. So I was confused by seeing a Density reading of 1.0229 which equates to a S.G. of 1.0245 (but again, S.G. isn't a choice on the Profilux).
Here is a nice table for conversions: https://reefapp.net/en/maintenance/calculator/unitconversion
I found that the values the Profilux show are a little different from the numbers that this calculator shows, for example, when temperature is 77.5F and Conductivity= 49.9:
.….....Profilux/Calculator
-Salinity: 32.7/32.5
-Density: 1.0229/1.0214
-S.G.: -------/ 1.0245
These were my actual readings today and my Digital Milwaukee reads 1.025.
So, my findings/comments:
-Although my salinity probe is only in use for 2 months, it has been very stable and accurate.
-I learned not to leave the setting on DENSITY because it is not the same as S.G. which I am more accustomed to using. (I leave it set on CONDUCTIVITY and target 51.0 (which = 1.0251 S.G. at 77.5F). I won't mind a little drift a little higher, though, not to exceed 52.7 (=1.026).
Here is a nice table for conversions: https://reefapp.net/en/maintenance/calculator/unitconversion
I found that the values the Profilux show are a little different from the numbers that this calculator shows, for example, when temperature is 77.5F and Conductivity= 49.9:
.….....Profilux/Calculator
-Salinity: 32.7/32.5
-Density: 1.0229/1.0214
-S.G.: -------/ 1.0245
These were my actual readings today and my Digital Milwaukee reads 1.025.
So, my findings/comments:
-Although my salinity probe is only in use for 2 months, it has been very stable and accurate.
-I learned not to leave the setting on DENSITY because it is not the same as S.G. which I am more accustomed to using. (I leave it set on CONDUCTIVITY and target 51.0 (which = 1.0251 S.G. at 77.5F). I won't mind a little drift a little higher, though, not to exceed 52.7 (=1.026).
