Refractometers

[mojomoo]

Yes, sorry meant test block. Although reading still tends to differ depending on position of test block on surface.

 

[psafloyd]

And a big THANK YOU to Rosti for posting up a fantastic *****'s guide video for using a refractometer on YouTube. To watch it, click HERE.

Thanks very much, Rosti. It covered EVERY single question or lack or surety I had about using the kit, even down to the cleaning of it.



Apparently 1d10t is a rood word...

 

[circe]

excellent video Rosti !!

 

[Dusty Rhodes]

We need more videos like this.

What a resource it would be!

Dusty

 

[Blue Spinnaker]

Excellent video - thank you Rosti.

 

[The Cumbrian]

Excellent video - thank you Rosti.

 

[keith pierce]

is there not one that you can buy that is already calibrated for honey

 

[oliver90owner]

They should be calibrated when new, but may not be, and can need recalibrating.

They are simply looking for the point where total internal reflection takes over from refraction ie where the Sine of the refracted ray becomes 1.00 (= 90 degrees) so the light goes along the boundry of the medium; any further increase in incident angle is reflected away from the scale - hence a light and dark boundary. Think of a fish's view from beneath the water looking out of the pond.

 

[alanf]

is there not one that you can buy that is already calibrated for honey

They are calibrated for honey. Or rather, in the ones sold for honey, the prisms are chosen and the scales set up for the refraction angle range that you might expect from honey. There are alternatives for the range useful when brewing for instance. The fine calibration is for when the optics are disturbed, for instance a hard knock or being dropped.

 

[Moggs]

Calibration is a means of adjusting the actual reading back to the manufactured state of accuracy. Instruments invariably lose their accuracy over time (environmental influence, mechanical shock, physical degradation, electrical instability, etc).

Some means of calibration is generally incorporated to trim out these inaccuracies (in the case of a honey refractometer, a calibration screw that acts on the scale - it is a purely optical device). Hence the need for a reference standard that is used to 'set' the reading to.

Some refractometers (e.g. salinity) are adjusted at 'zero' (using pure water) but our honey refractometer's scale does not extend down to the zero point (it couldn't cope with water and a saturated sugar solution within the same unit, the scale would be too wide for it to work) hence our need for a known reference that falls within our measurement range (and ideally, very close to our point of interest around 20% moisture - Rosti uses olive oil).

More sophisticated instruments may include a 'zero' and 'span' or 'range' adjustment to correct for zero and full scale errors respectively (useful if the calibration inaccuracy is not linear throughout its range).

 

[YorkshireBees]

A very informative video, I bought a refractometer last year and used it the first time this year.