Conductivity vs Refractometer

[Reef.]

Yeah not sure, I guess for the same reason the Hanna Satchets say to not use in the refractometer.

Not sure, as you are making a solution that reads 1.026 and that is what you are testing.

 

[Jeepjeep_0]

Yeah I argued that with Hannas tech line 1.026 is 1.026 right??? They said that conductivity measure differently so....... solutions different? I read an article by Randy Holmes-Farley that was very similar to what Hannah was saying so I found the other recipe he said to use for the conductive meter.
My ultimate question will be whether the Hannah and refractometer will read the same salinity level in my tank once calibrated with the proper solutions?

 

[Jeepjeep_0]

I know that stability is more important than numbers, generally speaking, but 1.030 made me nervous.

 

[Reef.]

Yeah I argued that with Hannas tech line 1.026 is 1.026 right??? They said that conductivity measure differently so....... solutions different? I read an article by Randy Holmes-Farley that was very similar to what Hannah was saying so I found the other recipe he said to use for the conductive meter.
My ultimate question will be whether the Hannah and refractometer will read the same salinity level in my tank once calibrated with the proper solutions?

I used the 3.65g one for my hydrometer and also my refractometer and both were correct


I can understand why you can’t use the Hanna, as it is probably not salt water at 1.026, some other kind of fluid with a conductivity of 1.026 so on a refractometer it will bento read right, what I can’t understand is, if you make salt water up at 1.026 and you are testing salt water at 1.026 why would the two calibration fluids need to be different?

I guess we’ll see when you try it, be sure to use both solutions on both readers to see what the results are.

 

[58e970b2-3f88-4897-87ba-5]

How big of a variance do you have between Your Hannah and hydrometer? Are you using the Hannah HI70024 35.00 ppt solution to calibrate the Hannah?

Tested at 24.9 - 25.0 C (according to Hanna temp reader)

Hydrometer: 1.025 sg (33.188ppt)

Hanna (pre calibration): 35.7 ppt (1.0269 sg)
Hanna (after calibration): 36.0 ppt (1.0271 sg)

I am using the Hannah Hl70024 calibration fluid. My previous calibration was early January (included just for curiosity).

Hydrometer is a sera Marin Hydrometer.

 

[Randy Holmes-Farley Verified Community Expert]

Not sure why they are different, if Randy’s diy recipe I’m sure there is a good reason but the 3.65g salt one should work for both as it will read 1.026.

They are different because my DIY is not a seawater mimic.

In short, the amount of sodium chloride in solution that matches the refractive index of 35 ppt seawater is not the same as the amount of sodium chloride in water that matches the density of 35 ppt seawater or the conductivity of 35 ppt seawater. All three must be different.

 

[Randy Holmes-Farley Verified Community Expert]

Yeah I argued that with Hannas tech line 1.026 is 1.026 right??? They said that conductivity measure differently so....... solutions different? I read an article by Randy Holmes-Farley that was very similar to what Hannah was saying so I found the other recipe he said to use for the conductive meter.
My ultimate question will be whether the Hannah and refractometer will read the same salinity level in my tank once calibrated with the proper solutions?

Unless the Hannah 53 mS/cm standard is seawater, they are correct. Most laboratory conductivity standards are not seawater.

 

[58e970b2-3f88-4897-87ba-5]

Tested at 24.9 - 25.0 C (according to Hanna temp reader)

Hydrometer: 1.025 sg (33.188ppt)

Hanna (pre calibration): 35.7 ppt (1.0269 sg)
Hanna (after calibration): 36.0 ppt (1.0271 sg)

I am using the Hannah Hl70024 calibration fluid. My previous calibration was early January (included just for curiosity).

Hydrometer is a sera Marin Hydrometer.

I remembered this being closer last time I checked... probably should have recorded it last time. Or maybe I am just bad at reading my hydrometer (I wish it was bigger). Or maybe this batch of Hanna calibration solution is off...

I am going to look into making some homemade calibration solution soon.

Does anyone have any advise for buying an accurate scale? I don't think the +/- 5g one in the kitchen is quite what I need.

 

[Randy Holmes-Farley Verified Community Expert]

I remembered this being closer last time I checked... probably should have recorded it last time. Or maybe I am just bad at reading my hydrometer (I wish it was bigger). Or maybe this batch of Hanna calibration solution is off...

I am going to look into making some homemade calibration solution soon.

Does anyone have any advise for buying an accurate scale? I don't think the +/- 5g one in the kitchen is quite what I need.

Amazon has cheap scales that read to 0.01 g and cheap calibration weights to verify the accuracy.

These are just examples (I've not used either one), but $30 will get both:

 

[Cory]

Amazon has cheap scales that read to 0.01 g and cheap calibration weights to verify the accuracy.

These are just examples (I've not used either one), but $30 will get both:

Ive actually purchased the cheap calibration weights for 3 of my scales and they all read very close. So i was happy.

 

[58e970b2-3f88-4897-87ba-5]

Thanks Cory and Randy. New scale and calibration weights should be arriving some time tomorrow.

I also want to validate the temperature on the Hanna. Have a thermometer ordered to compare with. Sounds like I can validate it using a container of ice water and boiling water. Then compare the Hanna and thermometer readings at 0C and 25C.

 

[Jeepjeep_0]

Here’s my testing results, weird part is that both with distilled water calibration and With the 3.65g salt / 96.35g water mix calibration, both my refractometers were significantly lower than the 1.030 I measured last week. Nothing changed in my tank other than about 12 gallons of ATO of RODI Water. Overall everything is well within the +/-1 on my Hanna HI98319 and +/- 2 on my refractometer.

 

[Jeepjeep_0]

This is the scale I ordered, came with (1) 50g calibration weight.
Very nice scale was a little finicky when trying to add or remove .01g of salt or water but a little patience went a long way.

 

[Jeepjeep_0]

Just did a 20 gallon/10% water change. Mixed my water to 1.021 per the Hanna calibrated to Randy’s conductive mix. This should bring down my salinity the little bit I wanted. Still rubbing my head why it was so high last week, I’m leaning toward a temperature issue

 

[Reef.]

Here’s my testing results, weird part is that both with distilled water calibration and With the 3.65g salt / 96.35g water mix calibration, both my refractometers were significantly lower than the 1.030 I measured last week. Nothing changed in my tank other than about 12 gallons of ATO of RODI Water. Overall everything is well within the +/-1 on my Hanna HI98319 and +/- 2 on my refractometer.

I would say the 1.030 was an testing error then, very easy to get a wrong reading using a refractometer, I’ve seem me do 3 readings before I get a correct reading, using a used pipette etc to add the salt water to the refractometer is enough to throw the results.

Least now you know you have some good accurate equipment to test with.

 

[Jeepjeep_0]

That was what was weird though, been using the Hanna for about 6 months. Brought my water in to get tested for comparison and the LFS tells me 1.030, I know the potential error so I go home get both my refractometers and both read exactly 1.030 as well. Now 5 days later highest readings at 1.027. I’m sure it was error on my part just so weird, had me nervous.