question about refractometer

[pontius]

got a refractometer today. it says it adjusts for temp, I don't know. I tested regular RO water to calibrate. the RO water was room temp (approx 70-72 degrees F), and the salinity is 1.000. I then tested the water in my tank. the temp there is 82 degrees F, and it says the salinity is 1.023. Is this the correct salinity, or does it have to be adjusted for Temp? my hydrometer says the salinity in my tank is closer to 1. 025.

 

[birdy]

From my experience the refractometer is usually always right. As long as you calibrate your refractometer to room temp water then it will automatically adjust to the temp of the water.
I would trust the refractometer, it is very common for hydrometers to be off.

 

[92protruck]

I think you calibrate using distilled or RO/DI water (0 TDS - pure water). RO is not normally pure and would not be the best choice for calibration. IMO.

 

[beth]

Originally Posted by 92ProTruck
I think you calibrate using distilled or RO/DI water (0 TDS - pure water). RO is not normally pure and would not be the best choice for calibration. IMO.

That is correct. You calibrate using DI water at room temperature [there should be directions with the refract to help you]. Then use the refract on your salt water. Occasionally, recalibrate using DI water.
Take care when you clean the refract lens because the salt in the water could scratch the refract lens. So be gentle.

 

[pontius]

Beth, the directions with my refractometer are awful, many mispelled words and many sentences that don't make any sense at all. they do say though, that the refractometer is calibrated before it leaves the company, so I guess for now, it is right. so the salinity does NOT have to be adjusted for temp, right? when I tested with the RO water, it came out at 0, which is what plain water SHOULD test at, so I should be ok right? the biggest question is if I should be concerned that the RO was room temp and the tank water is 82F?

 

[bang guy]

Originally Posted by Pontius
I then tested the water in my tank. the temp there is 82 degrees F, and it says the salinity is 1.023.
1.023 is not a salinity reading. You're reading the specific gravity scale. Look over to the right side at the salinity scale and keep your salinity above 35ppt. When you put a drop of water on the lens and wait 30 seconds you're reading the salinity at room temp and it will be accurate.
Now that you have a refractometer you no longer need to bother with Specific Gravity and adjusting for temperature to derive salinity. You can read the salinity directly so use the salinity scale.... 35ppt....

 

[pontius]

ok, thanks Bang, I get it now. so how will have to occasionally test regular water to see if it needs to be recalibrated, right?

 

[bang guy]

Originally Posted by Pontius
ok, thanks Bang, I get it now. so how will have to occasionally test regular water to see if it needs to be recalibrated, right?
Calibration fluid will make it more accurate but adjusting it to read RO/DI water as 0ppt is accurate enough.