strange iSpindel readings

[Blinky]

Im wondering if this is the result of either or both as its the first time Ive added Lactose and also the first time fermenting under pressure..... My wort from the refractometer was reading 1059 (although now I think of it, its also brand new, could it be faulty?) but the iSpindel read 1070 - never thought anything of it, as its not been fully calibrated and I just use it to give an idea of when fermentation is over, but today, its reading a steady 1006, I cant see how it can be reading too high at the start and too low at the end?
This is the recipe: Grainfather Community Tools

 

[Blinky]

Dont know why I didnt think of this! Just checked with the hydrometer and its at 1012 which is spot on what the recipe predicted! Sneaky sip, its warm and filled with hops and yeast but its got oodles of flavour and a good bitterness on it. Amazing body but thats probably due to how much suspended material there is in the sample!

 

[peebee]

Calibration of these floating hydrometer gizmos is always a "two point" (at least) thing. One "point" will be to have it read 1.000 in 20°C water, the second should be at, say, 1.050 in a 20°C calibrated sugar solution. I skip the second point and always calibrate a second point at the starting gravity of each beer brewed (measured by a decent hydrometer or like). That way these hydrometers are always calibrated for the beer wort it is in.

Because it is a "two point" (at least) calibration its perfectly normal for any mis-calibration to be worse, or better, at either end of its range.

 

[Blinky]

Ah ok, cheers, that makes sense.

 

[phildo79]

You need to calibrate both devices. The refractometer is easy, the ispindel not so much. It's quite time consuming an fiddly. I bought mine to let me know if I had a stuck fermentation or not. I wasn't overly concerned about accurate readings but I now wish I had of calibrated it properly the first time out. It still works but I will be recalibrating it again soon.

I ferment in a 23L corny and once the lid is on and blow off tube attached, it doesn't get opened again (except for dry hopping) to minimise oxygen contact. So the ispindel seemed perfect and at a much more reasonable price.