Refractometers

[Truck]

ok im planning on buying a refractometer as ive heard hydrometers arent accurate.

so what can they be used for? testing temperature and SG.

how do they work or how do I use it?

ive posted it here because you can measure Sg in marine, brackish and temperature needs measuring in all aspects of the hobby.

 

[barker_23]

Refractometers only measure salinity, not temp

 

[Truck]

oh right ive seen one advertised that does

 

[barker_23]

Oh right, not seen them before, sorry

 

[saz326]

Refractometers measure the angle at which light refracts through a sample of water. Whether salted, or fresh. Any fluid to be honest.

It will not give readings of temperature in the same way. It probably has a temperature probe hidde away somewhere - or maybe a plug in one.

Bear in mind that if it measured the temperature of water in the same way as measuring the refraction, then the sample would have time to cool down in the instrument and so give a false reading.

 

[Straydum]

haven't heard of any that tell temperatures but i guess its possible, just that it would probably cost quite a bit. i'm trying to get my hands on one (for just sg) but if you're using it only for freshwater, spending the money on a good thermometer would be better

 

[Truck]

its for marine ive used a hydrometer before, and i hate calibrating it all the time

 

[andywg]

Refractometers meaure the refractive index of the liquid sampled. The refractometer you buy will have a scale to convert this reading into something more useful (usually salinity and SG at 25 degrees on salinity refractometers).

At the levels we purchase hydrometers are more accurate than refractometers (especially if you calibrate the refractometer to zero) but many people do not know how to use them accurately.

 

[Truck]

i know i have to calibrate my hydrometer in RO water is there anything else im missing? i only dip it in the water to test salinity every morning for about 30 seconds, and the wipe it clean.