Refractometer calibration

[j-bert]

Hello all, I have been noticing that when I calibrate my refractometer with my 35ppt solutions when I test tank water, then double check calibration with 35ppt solution, the numbers are NEVER the same. Why is my refractometer not staying calibrated.

Thank you!

 

[rayadog]

Silly question. Do you rinse with RO DI water after each read?

 

[j-bert]

Silly question. Do you rinse with RO DI water after each read?

Honestly no, I wipe with a clean cloth and that’s it. Do you think this could affect it that much?

 

[orangestorm]

I’ve faced this same issue and gathered a couple tips.

1. Calibrate using refracto juice once before a water change and don’t try recalibrating it. Just trust that it’s calibrated correctly.

2. Use the same light for each reading.

3. Rinse with water and dry off with microfiber cloth before use again.

4. Ensure you’re not in a cold room or running cold water when rinsing the tool if you’re going to run another reading.

5. Dedicate one dropper for measuring salinity and don’t use it for anything else.

Hope these help!

 

[slingfox]

If you got one of those cheopo refractometers online or from an LFS it is doubtful it can be trusted, particularly if it didn’t even hold calibration after one salinity check.

Note also that most of the store bought calibration solutions can’t be trusted. You can check the calibration using a cheap DIY solution:

https://www.reef2reef.com/ams/reef-aquarium-salinity-diy-calibration-standards.956/
Also, yes, after each test you should rinse your refractometer either RODI and wipe dry.

 

[j-bert]

If you got one of those cheopo refractometers online or from an LFS it is doubtful it can be trusted, particularly if it didn’t even hold calibration after one salinity check.

Note also that most of the store bought calibration solutions can’t be trusted. You can check the calibration using a cheap DIY solution:

https://www.reef2reef.com/ams/reef-aquarium-salinity-diy-calibration-standards.956/
Also, yes, after each test you should rinse your refractometer either RODI and wipe dry.

Thank you for the input, I’ve honestly just went out and got myself the tropic marin hydrometer to avoid the refractos

 

[mh0ward]

Honestly no, I wipe with a clean cloth and that’s it. Do you think this could affect it that much?

100%. Not sure what you use, but I use the Milwaukee MA887 and the amount of sample you put on the glass is small enough that any leftover salt residue can contribute fairly significantly. I wipe any saltwater off the refractometer with a clean paper towel and then use a wash bottle of RODI to clean the lens again, and dry that up with a different towel.

I also usually use a new plastic syringe to take a sample from the tank or water that I’m mixing up. I used a new one to pull maybe 2 ml of saltwater to test then emptied the syringe of what was left over, needed to re-measure maybe 30 minutes later and hadn’t cleaned the syringe, and the leftover salt residue on the syringe was enough to read 1.033…. Pulled out another new syringe to double check and it was 1.025.

 

[slingfox]

Thank you for the input, I’ve honestly just went out and got myself the tropic marin hydrometer to avoid the refractos

When you get the TM Hydrometer, please post your results so we can see if the refractometer was right or not

 

[GSPClown94]

Honestly no, I wipe with a clean cloth and that’s it. Do you think this could affect it that much?

Sounds like your refractometer doesn't have automatic temperature control or it is broken. Depends on how much you are wiping the prism between readings. Friction from wiping the prism clean can definitely generate enough heat to change the reading when ATC is broken or nonexistent.

 

[TheReefAbides]

I was having a similar issue. not so much inconsistency but a different SG compared to my LFS.

I originally calibrated my Refractometer using the refracto juice form BRS. Followed all instructions. Set refractometer to 35PPT 1.026 SG. Had been mixing salt water to this calibration. all is holding fine at this number.

took a water sample to my LFS for peace of mind before getting new tank mates.

He uses the milwaukee digital refrac. his reading was 1.024.... head scratcher for me. I like consistency...

I went back home double checked with juice and temps and tank etc. reading 1.026.. hmmm

ordered a TM Hydrometer and a 500ml graduated cylinder.. Just received tonight, tested and low and behold the reading was 1.0242!

so either there is an error in my methods or the juice is not accurate, and from what I've read.. this may be the case.

I tried Randys home made solution last week, but I should have waited.. will retest with this and the hydrometer in the near future.

my only question is, if I am going to calibrate my refrac to the hydrometer, how do I account for the temp difference??

EDIT: recent research reading stated"1.0266 at 20°C, which changes to 1.0264 at 25°C"

 

[larrysaltisfun]

If you got one of those cheopo refractometers online or from an LFS it is doubtful it can be trusted, particularly if it didn’t even hold calibration after one salinity check.

Note also that most of the store bought calibration solutions can’t be trusted. You can check the calibration using a cheap DIY solution:

https://www.reef2reef.com/ams/reef-aquarium-salinity-diy-calibration-standards.956/
Also, yes, after each test you should rinse your refractometer either RODI and wipe dry.

Thank you for the input, I’ve honestly just went out and got myself the tropic marin hydrometer to avoid the refractos

That’s exactly what I did. I just handle it like it’s made out of 24 karat gold. I also have a cheap instant ocean hydrometer, which is consistently off by the same amount than what my tropic Marin hydrometer yields so I use that most of the time and just adjust a little bit.

 

[TheReefAbides]

That’s exactly what I did. I just handle it like it’s made out of 24 karat gold. I also have a cheap instant ocean hydrometer, which is consistently off by the same amount than what my tropic Marin hydrometer yields so I use that most of the time and just adjust a little bit.

funny you say that, I opened the case to it.. stopped breathing and told my self not to sneeze

 

[redfishbluefish]

Hello all, I have been noticing that when I calibrate my refractometer with my 35ppt solutions when I test tank water, then double check calibration with 35ppt solution, the numbers are NEVER the same. Why is my refractometer not staying calibrated.

Thank you!

How is your little flapping door swinging on your Refractometer. A stiff door will result in funny numbers. Check out this post:

Lubricate Your Refractometer

 

[BeanAnimal]

He uses the milwaukee digital refrac. his reading was 1.024.... head scratcher for me. I like consistency...

The device is a toy, not precision instrument. Just read the specs.

I e is an error in my methods or the juice is not accurate, and from what I've read.. this may be the case.

Most of the hobby grade standards are garbage. Use Randy’s DIY.

my only question is, if I am going to calibrate my refrac to the hydrometer, how do I account for the temp difference??

Here ya go.

https://beananimal.com/tools/tropic-marin-precision-hydrometer-correction-calculator/

 

[TheReefAbides]

He uses the milwaukee digital refrac. his reading was 1.024.... head scratcher for me. I like consistency...

The device is a toy, not precision instrument. Just read the specs.

I e is an error in my methods or the juice is not accurate, and from what I've read.. this may be the case.

Most of the hobby grade standards are garbage. Use Randy’s DIY.

my only question is, if I am going to calibrate my refrac to the hydrometer, how do I account for the temp difference??

Here ya go.

https://beananimal.com/tools/tropic-marin-precision-hydrometer-correction-calculator/

Thank you