misco refractometer

[rinconmike]

anyone have one of these? i just got one. pretty nice device. they said i never have to calibrate, just set zero with ro/di water. also, every once in a while clean the glass with rubbing alcohol.

just checking to see if anyone has different information

http://www.misco.com/products.php?productid=440


thanks,

mike

 

[disc1]

Trust them? I'd check it with a 35ppt solution just to be sure.

 

[bertoni]

I agree. I wouldn't trust any SG or conductivity device calibrated only at zero.

 

[rinconmike]

thanks guys. I did check with 35ppt solution and it reads 35.

They said using the RO/DI water is setting it to zero and not calibrating. Not sure if there is a difference, but they said it is and it can only be calibrated in the lab.

Mike

 

[Randy Holmes-Farley]

That's a semantic point that isn't important. If it reads the 35 ppt properly, you are good to go.

 

[rinconmike]

thanks. I just doubled checked with pinpoint solution (I used a different one the other day) and it reads 35 Practical Salinity Units (PSU) and 1.0264 (Specific Gravity D20/20 ).

It's accuracy is +/- .0005 for SG and +/- 1 for PSU so I guess it is reading correctly.

However, the Conductivity (mS/cm @ 20'C) reads around 47 (I forgot to write it down) and not 53 that I thought it should.

Also, anyone think there is an issue with cleaning with rubbing alcohol (70% isopropyl) every once in a while.

thanks,

Mike

 

[Randy Holmes-Farley]

The 53 mS/cm for the Pinpoint and 35 ppt seawater is normalized to 25 deg C, and your unit uses 20 deg C. I'd just ignore that unit of measure.

 

[rinconmike]

thanks,

Mike

 

[Randy Holmes-Farley]

:thumbsup:

Happy Reefing.