Rapt pill OG reading accuracy

[Jean-Raphael Lavoie]

I calibrated my RAPT pill twice with the simple methode and still it's reading 0.007 lower than my hydrometer and my refractometer in wort. My hydrometer is calibrated at 68F and I do compensate for the temperature of the wort. My refractometer gives me a pretty close reading (within 0.002) of my hydrometer in wort.

It's the second batch in a row that the OG reading of the RAPR T pill is off by 0.007.

Question: Does anyone else have found a difference between the RAPT pill OG reading and their hydrometer?

My next move will be the verify the calibration of my hydrometer in distilled water at 68F. If my hydrometer is off, I,ll update this post.

I include graphic of the RAPT pill left in tap water over a periode of 24 hours just to show that the reading will change event in tap water.

 

[hotbeer]

Well you did have a big temperature excursion at the time you are showing on the graph. But that only accounts for 0.001 of hydrometer error.

I wouldn't be too fiddly about it and worry about getting it less than 0.002. If it happens to be less great. If not, just remember the correction.

The sharp change in SG and temp seem to suggest something happened. Maybe it was just hung up on the side of the container. Though I'm not sure what explains the temp changing so fast.

I use my RaptPill as a relative measure so I can see what's going on in the FV. I don't really care how accurate the SG it reports is. Just so long as it's consistent.

I use the hydrometer to get more exact measures. Usually just the OG and FG.

 

[Jean-Raphael Lavoie]

Well you did have a big temperature excursion at the time you are showing on the graph. But that only accounts for 0.001 of hydrometer error.

I wouldn't be too fiddly about it and worry about getting it less than 0.002. If it happens to be less great. If not, just remember the correction.

The sharp change in SG and temp seem to suggest something happened. Maybe it was just hung up on the side of the container. Though I'm not sure what explains the temp changing so fast.

The graph was made in tap water and the temperature change is just due to temperature fluctuation in my house over a hot summer day. I ferment in the basment dont worry. But I was supprise to see a change of gravity in water.

Do you experience a difference between your hydrometer and the Raprt pill reading?

 

[hotbeer]

I calibrated it when I got it 9 or so months ago. I use it quite a bit, but like I said, I'm only interested in relative things that are going on in the FV. It's doesn't matter if they are the actual SG reading since I use a hydrometer to measure the actual OG and FG. The last time I noted a difference, the RaptPill was about 0.002 higher reading for SG than the real hydrometer. That was about two months ago when I noticed.

My RaptPill could be off by any amount, but if it's consistently the same error, it still would tell me quite a few things. Whether or not fermentation is happening, when the ferment ended, what the relative change of SG is so I can estimate my ABV. And probably some other stuff too. Which is the stuff I really care about when it's in the FV.

 

[jwill911]

I agree with using the Pill for relative changes in gravity, and I compare to EasyDens, it is very accurate IMO. Current batch EasyDens = 1.025, Pill = 1.024, that’s close enough for me. My big complaint with the Pill is temperature. My temp controller thermowell will show steady 68 degrees (f) and Pill shows 64 degrees. I’ve played with temp offset and not made progress.

 

[advaitbanga]

Hi,
I also had exact same issue. Off by 0.007.
I was so confident on rapt pill all this time. Its 3rd brew with rapt pill but this it seemed it was way off that i was depressed that i missed 10 points off the calculated one although i used a new cooler mash tun but i had problems reaching mash temp. Dont know why.. but it showed 1.041 and I just pulled out the fermenter and thought of checking with my hydrometer. He made my day. Its around 1.049-.1048...
Dont know why?

 

[Simon0x]

My first batch with the pill worked great and the values seemed to match my hydrometer reading.

My second batch however is showing 1.020 SG while my Hydrometer reads 1.011 SG. Thats a 0.009 SG difference! Fermentation seems to be done and it's off by only 0.001 my estimated value. I tried to give my fermenter a little shake to see if the value adjusts but it didn't. I don't have much Kräusen and the pill looks happily floating without much residue on it. I calibrated the pill before using.

I will opt in for the EasyDense and keep using the Pill just to check the progress of fermentation.

I will update once I keg the beer. I will check if the pill still shows 1 SG in Water.

 

[VTMongoose]

I do advanced calibrations with mine periodically on brew days. I immerse it in starsan, calibrate at 1.000, then throw it in the fermentor with my yeast and punch in whatever my hydrometer/refractometer tells me the OG is. Pills are honestly really good out of the box even with the simple (water) calibration, unlike my two TILTs which were off by 0.020 or more. Either way you can't practically use floating hydrometers for true accurate readings of original and final gravity IMO.

 

[Brewer Mike]

FYI - you can mix up a salt water solution for the high end of the advanced calibration. I forget the ratio I used, but it wasn't a whole lot of salt, which is really cheap anyway.
I keep the house pretty cool at night - 60 in the winter. I had 2 pitchers, one with 1/2 gallon of distilled water & one at 1.070 salt water. Leave them overnight so both are at 60 degrees. Verified the 1.070 against my hydrometer which is calibrated at 60. Then calibrate.

Also, for temp adjustment, remember that the tube acts like a thermos. It'll take a while for the temp to equalize.

 

[BongoYodeler]

My personal experience - I have two of them, and bought the wireless charging setup for both. This mostly eliminates having to open the Pill.

I calibrate them for SG occasionally, but I find it stays quite close to actual through several brews. For instance for the past 3 or 4 brews I haven't even calibrated it. Strangely enough though my Pill's OG reading seems to consistently be around .007 below my hydrometer reading, but it always ends up matching FG exactly. The temperature is always very close to actual when compared to an instant read thermometer.
Bottom line regardless of the actual SG the Pill reports I can always tell when fermentation finishes, which negates the need to open the fermenter to take hydrometer readings to verify FG.

 

[Simon0x]

I just figured out something while cleaning the pill. It seems like I did not close the pill properly enough which caused the electronics inside to move up and down as well as to the sides. This could have cause the off reading for me. At the end of my fermentation, I gave my fermenter a little shake and it seems like the pill reported the correct values again. I will give it another try.