Difficulties measuring salt level accurately

[TheHarold]

I love my Milwaukee digital refractometer and will never change to anything else. Reads perfectly every time, and every few months I calibrate it with a 0ppt solution and certify accuracy with a 35ppt solution.

Just needs 1 drop of water

Milwaukee Digital Seawater Refractometer

An excellent digital refractometer that is able to provide results in 3 different scales.

www.jlaquatics.com

 

[homer1475]

Also please note that the temp of refractometer will affect the reading so it should be close to tank water temp and not 10-20 degrees cooler.

If your refractometer says ATC on it, the water temp and instrument temp does not matter. The reading curve is automatically compensating for.

Seriously read the instructions on an ATC refractometer or watch the BRS video on them. They all say the same thing regarding instruments that have ATC.

 

[Super Fly]

If your refractometer says ATC on it, the water temp and instrument temp does not matter. The reading curve is automatically compensating for.

Seriously read the instructions on an ATC refractometer or watch the BRS video on them. They all say the same thing regarding instruments that have ATC.

even though mine says ATC, it's definitely not ATC. Like I said, if left in basement, mine will give different reading vs when unit is similar temp to tank water. Bought it from Amazon as ATC w label but definitely not ATC.

 

[homer1475]

Are you sure its' not a BRIX refractometer?

 

[Super Fly]

Are you sure its' not a BRIX refractometer?

yes, I'm cheap so bought a no name brand from Amazon... guess u get what u pay for in this case.

 

[birdy123]

Just found this on tropic marine website in regard to readings of refractometers.....
ts taken a while, but I am now happy with the measurements.

I believe the following points should be highlighted to customers with this device:
1. You will NOT get reproducible results if you use too much RO water to clean between each measurement (also only need 3- 4 drops of solution, no more). I found it is best to use 2 lens cloths - one to wipe sample away and the other to final clean no rinsing with RO at all.
2. You will get apparent drift in calibration if you DO NOT leave the refrac out in the open in the room that measurement will be taken for some time for temperature of refrac to equilibrate. I was storing refrac in its box in a cupboard in the room where I was taking readings, and this was sufficient to cause daily discrepancies in readings.

 

[tstar]

See? I wasn't kidding when I said to get everything to the same temp! lol

Tim

 

[Quietman]

As a general rule with all test equipment you need to calibrate for range expected to see or a max and min that covers the range.

Best pH are 4.0, 10.0, 7.0 (last being optional, but I do it). Salinity - 35.0 and make sure you allow temps to equalize (if calibration liquid is colder storage), I also use known standards periodically for all my titration test kits to verify my "calibrated" eye balls.

And repeated open and closed fluids can lose calibration accuracy on certain parameters as well.

 

[the_chef_pierre]

Hey everyone. So my lfs was actually able to measure my salinity and they read it at around 1.024 (which is close to the 1.025 i find when calibrating with RODI water as opposed to the 1.020 reading i was getting using the calibration fluid). They told me that I could be experiencing this problem due to my calibration fluid possibly being off. I only just purchased it but theres no visible expiration date on the bottle. Wondering if this was maybe just sitting on their shelves for too long. Either way, I plan on sticking with my original calibration with the RODI water since this is what the manual for my refractometer states and gives me the closest reading to what the lfs found. Thanks again guys for all the help and support with this.

 

[Waters]

I love my Milwaukee digital refractometer and will never change to anything else. Reads perfectly every time, and every few months I calibrate it with a 0ppt solution and certify accuracy with a 35ppt solution.

Just needs 1 drop of water

Milwaukee Digital Seawater Refractometer

An excellent digital refractometer that is able to provide results in 3 different scales.

www.jlaquatics.com

I wish mine was that accurate lol. I calibrate before every use (as instructed) and it will still sometimes read incorrectly (normally high). I then re-calibrate and it reads correctly. Do you wait for the temp of the water to stop moving before you test? Maybe I need to stop calibrating lol.

 

[fcmatt]

You bought calibration fluid from a local fish store? I would not recommend that if that is the case.... my lfs sells a couple test kits that are expired from 2012 for example....

You have to buy that stuff from a high volume seller.

 

[TheHarold]

I wish mine was that accurate lol. I calibrate before every use (as instructed) and it will still sometimes read incorrectly (normally high). I then re-calibrate and it reads correctly. Do you wait for the temp of the water to stop moving before you test? Maybe I need to stop calibrating lol.

The way you describe it sounds like you are leaving salt water on it, which evaporated to form salt and give a false (yet true) high reading of your sample. That is why your first test is abnormally high, yet the second one works (since excess salt is gone).

 

[Thespammailaccount]

The Hanna salinity is good for checking newly mixed saltwater I will is it on occasion to check the temp. The Milwaukee digital salinity is the instrument I trust

 

[madweazl]

There are a couple easy ways to get a sanity check. First, what salt are you using? When you mix it up to what you believe is 1.026 (or whatever your target is), what are your alkalinity, calcium, and magnesium levels? If they're lower than what the salt manufacturers suggests, your salinity is probably low (you need to look at all three).

A sure fire method is to use Randy's calibration standard. I'd trust my dog testing the aquarium more than the LFS.

Also, calibrate every single time you use the device.

 

[Uncle99]

It is more important to provide a stable salinity than whether it’s a point, up or down.
My swing arm says 1.024
My calibrated refractometer says 1.025
Lab testing confirms, it’s actually 1.027
Look like it’s been 1.027 for three years instead of 1.025

no losses and everyone happy