Hydrometer vs refactometer

[friendlyAlien]

Hi,

I have a tropic Marine hydrometer that reads 1.24 salinity at 78 degrees water temp. I also have a freshly calibrated hydrometer that reads a solid 37 - converted to 1.26.

I know it may not matter but it bothers me.

Calibration fluids came with the hydrometer and are at room temperature 72 degrees. Is the shift this high for temp?

Would love all of your opinions. How to get these devices to say the same thing?

 

[Randy Holmes-Farley Verified Community Expert]

Hi,

I have a tropic Marine hydrometer that reads 1.24 salinity at 78 degrees water temp. I also have a freshly calibrated hydrometer that reads a solid 37 - converted to 1.26.

I know it may not matter but it bothers me.

Calibration fluids came with the hydrometer and are at room temperature 72 degrees. Is the shift this high for temp?

Would love all of your opinions. How to get these devices to say the same thing?

What calibration fluid?

 

[Randy Holmes-Farley Verified Community Expert]

Which refractometer?

 

[friendlyAlien]

I used this one that came with the coral view salinity probe which also shows 37 after calibrating.

 

[friendlyAlien]

The refractometer brand is ATC.

 

[rtparty]

You will drive yourself mad trying to get them to match.

The Tropic Marin hydrometer is the way to go.

 

[Uncle99]

If you’re referring to those plastic Hydrometers, they are not considered by many to be as accurate as a calibrated refractometer.

I have that refractometer. Works great for years.

The hydrometer, well, Mines useless, always a bit higher….

 

[Randy Holmes-Farley Verified Community Expert]

I used this one that came with the coral view salinity probe which also shows 37 after calibrating.

That fluid, even if perfectly made, may not be suitable for either refractometers or hydrometers. It is made for conductivity meters, and those fluids are not necessarily interchangeable.

 

[friendlyAlien]

That fluid, even if perfectly made, may not be suitable for either refractometers or hydrometers. It is made for conductivity meters, and those fluids are not necessarily interchangeable.

Ok, so you say these calibrations fluids are more than just salt water?
What is the difference?

If course the probe also says 37 ... But I was trusting the probe the least.

 

[gbroadbridge]

The refractometer brand is ATC.

ATC is not a brand - it simply refers to Automatic Temperature Compensation.

I've seen many cheap refractometers such as these on many marketplaces.
If you calibrate them using a suitable fluid they are generally okay, but I don't trust the ATC part much.

Make your own calibration fluid and use that rather than an expensive purchased product.

 

[Randy Holmes-Farley Verified Community Expert]

Ok, so you say these calibrations fluids are more than just salt water?
What is the difference?

If course the probe also says 37 ... But I was trusting the probe the least.

I do not know exactly what they put in them, but I have an article that gives diy recipes for salinity standards using sodium chloride, and they MUST be different concentrations to be 35 ppt on hydrometers, conductivity meters, and refractometers.

One could make a single standard that had many seawater ions in it, but there’s no reason to make them so complicated.

 

[friendlyAlien]

Thank you, will read with interest.
I have to admit it was confusing that we use different salt concentrations for the same salinity. Didn't think about the interference with all the other ions.

 

[Fritz05]

Hydrometer comes calibrated out of the box and does not lose calibration. As long as the water temperature is appropriate, it will be accurate.

 

[Randy Holmes-Farley Verified Community Expert]

Hydrometer comes calibrated out of the box and does not lose calibration. As long as the water temperature is appropriate, it will be accurate.

Assuming it is properly calibrated on manufacture, and the paper inside has not moved since manufacture, I agree.

But because those two things are possible, I think it is always worth checking any hydrometer against a standard at least once.

 

[friendlyAlien]

I want to share my results because this is so much fun. I mixed the 2 liter Coke bottle calibration solution and calibrated my refractometer to 35ppt.

My tank water reads 34.5ppt.
The hydrometer puts me at 1.0255 salinity at 78 degrees in the tank. Sadly that thing is too big to stick into the 2 liter table salt calibration mix. I need a much taller /thinner testing vessel here.

The salinity probe connected to Hydros puts it at 41ppt - definitely way off

I then also tested the calibration fluid for the probe. For the 35ppt calibration fluid, I got 33ppt, and for the 28ppt calibration fluid, I got 27ppt.

What a fun experiment with frustrating results. Chasing perfection will be hard.

 

[gbroadbridge]

I want to share my results because this is so much fun. I mixed the 2 liter Coke bottle calibration solution and calibrated my refractometer to 35ppt.

My tank water reads 34.5ppt.
The hydrometer puts me at 1.0255 salinity at 78 degrees in the tank. Sadly that thing is too big to stick into the 2 liter table salt calibration mix. I need a much taller /thinner testing vessel here.

The salinity probe connected to Hydros puts it at 41ppt - definitely way off

I then also tested the calibration fluid for the probe. For the 35ppt calibration fluid, I got 33ppt, and for the 28ppt calibration fluid, I got 27ppt.

What a fun experiment with frustrating results. Chasing perfection will be hard.

I'm not sure if you understood that the calibration solution is different for each type of measurement device.

The same DIY recipe cannot be used for the Hydrometer, Refractometer or Electroconductivity meter.
They are all different calibration solutions.

 

[KStatefan]

I want to share my results because this is so much fun. I mixed the 2 liter Coke bottle calibration solution and calibrated my refractometer to 35ppt.

My tank water reads 34.5ppt.
The hydrometer puts me at 1.0255 salinity at 78 degrees in the tank. Sadly that thing is too big to stick into the 2 liter table salt calibration mix. I need a much taller /thinner testing vessel here.

The salinity probe connected to Hydros puts it at 41ppt - definitely way off

I then also tested the calibration fluid for the probe. For the 35ppt calibration fluid, I got 33ppt, and for the 28ppt calibration fluid, I got 27ppt.

What a fun experiment with frustrating results. Chasing perfection will be hard.

I'm not sure if you understood that the calibration solution is different for each type of measurement device.

The same DIY recipe cannot be used for the Hydrometer, Refractometer or Electroconductivity meter.
They are all different calibration solutions.

Randy has a great article on this subject

 

[friendlyAlien]

Right that is the method I used to create the calibration solution. I can't use that to calibrate my hydrometer? I thought that is the whole point ... reading again.


And yes, still trying to wrap my head around (and showing to myself) that I really can't use the different calibration methods fluids. It is still counterintuitive to me ... (not doubting just being puzzled by it)

 

[KStatefan]

Right that is the method I used to create the calibration solution. I can't use that to calibrate my hydrometer? I thought that is the whole point ... reading again.


And yes, still trying to wrap my head around (and showing to myself) that I really can't use the different calibration methods fluids. It is still counterintuitive to me ... (not doubting just being puzzled by it)

No There are three different standards in the article.

 

[SteveMM62Reef]

The Plastic Swing Arm Hydrometers need to be conditioned. A new one I soak in my Saltwater mixing container for 48 hours. They say 24 hours, but I get better results going longer. If I clean it and dry it, or it’s been a long time between usage, I soak again. Usually 12 hours is enough.