Rapt Pill tilt error

[aussiewasp]

Hi,

I have been using the Rapt Pill for a few batches and monitoring against a hydrometer whilst I get proficient at using it.

My latest batch, a heavy Coopers Smooth Bockinator the FG has gone kaput. At around day 7 and for the next 5 days the gravity remained steady at 1.017. This was telling me alcohol was at just under 4%....wrong or had the yeast died.

I have just used the hydrometer and it comes in with correct alcohol of 7.7%

I bottled and think I found the issue, see attached photo. Maybe not the most accurate measure for brews with a significant scum level? 

[Shamus O'Sean]

@jpd1009, you could scrape it off mid-ferment with a sanitised/sterilised stainless steel spoon.  I use iSpindels that have a flat top cap.  They capture even more crud.

[Cheap Charlie]

I have one and it has a ring around it most ferments. The graphs seem ok, but I guess I wouldn't know. I figure it has minimal effect, it would be less than 1 point. As I'm not performing rocket surgery I don't care, I'm just happy I don't have to take gravity samples all of the time and can leave the ferment do its thing. I've given up on trying to calculate abv, as these brews always seem stronger than commercial brews at the so called same abv. These days I judge them on how many bottles to get rockin' - 2 bottles and she's 5% and under, 1 bottle and she's 6%+. It does seem strange though that there is such a huge difference in your results. For what it's worth, where my pill measures 1.013 my hydrometer measures 1.012, but the thing is how do I believe either of them?

[aussiewasp]

I am going to calibrate the pill again and see how we go.

[Cheap Charlie]

1 minute ago, jpd1009 said:

I am going to calibrate the pill again and see how we go.

that was my next suggestion, it seems fairly bulletproof for me anyway, cheers

[kmar92]

16 minutes ago, jpd1009 said:

I am going to calibrate the pill again and see how we go.

I would suggest that you use the 2 point calibration for better accuracy. I have been using RAPT pills extensively, every brew, and I haven't had the problem that you have encountered. There has always been a ring of krausen on the pill in each brew I do but it does not seem to affect the accuracy unduly. Keep in mind that the RAPT pill will never be super accurate with the SG readings that it gives, it is meant to be a guide to how fermentation is going rather than being a completely accurate SG reading. I still use a hydrometer to take an OG reading of a brew and then when the RAPT pill is indicating a stable SG over a few days I then take a reading again with a hydrometer to get an accurate FG. The hydrometer and RAPT pill readings do vary a few points but remain within a stable ratio of difference over the ferment.

I have just converted 1 of my RAPT pills to wireless charging in order to eliminate the need to calibrate the RAPT pill everytime it is opened to charge or to enter the AP captive portal. I did a 2 point calibration after installing the wireless charging kit and I am interested to see how accurate it is with the next ferment.

[ozdevil]

24 minutes ago, kmar92 said:

I have just converted 1 of my RAPT pills to wireless charging in order to eliminate the need to calibrate the RAPT pill everytime it is opened to charge or to enter the AP captive portal. I did a 2 point calibration after installing the wireless charging kit and I am interested to see how accurate it is with the next ferment.

i will definitely be interested  in how you go with this,  i have only did the 1 point calibration  however this weekend i plan to make a sugar mix up to do the 2 point calibration   like you i do not want to be calibrating each time until the battery goes dead.

@jpd1009  the wireless charging unit will be a great addition for your pill   and will prolong the life of the O-rings as well as the calibration that has been mentiond by kmar

 

 

[kmar92]

42 minutes ago, ozdevil said:

i will definitely be interested  in how you go with this,  i have only did the 1 point calibration  however this weekend i plan to make a sugar mix up to do the 2 point calibration   like you i do not want to be calibrating each time until the battery goes dead.

Yep that is what I did. 1st calibration was done in water and the 2nd calibration I mixed up a sugar solution which read 1.049 with my calibrated hydrometer and that is the reading that I used in the calibration. I have previously played around with the temperature calibration of the RAPT pill, but I found that I was just chasing my tail with that so I have left the temp calibration offset at 0.

See what happens with the next ferment!

[kmar92]

On 3/6/2023 at 9:16 PM, kmar92 said:

Yep that is what I did. 1st calibration was done in water and the 2nd calibration I mixed up a sugar solution which read 1.049 with my calibrated hydrometer and that is the reading that I used in the calibration. I have previously played around with the temperature calibration of the RAPT pill, but I found that I was just chasing my tail with that so I have left the temp calibration offset at 0.

See what happens with the next ferment!

So first try of the RAPT pill with the wireless charging conversion and the 2 point gravity calibration was a bust. Put it into the FV with the AG brew that I did yesterday and it reported the SG as 1.034, when in fact it was 1.049. I must have done something wrong with the 2 point calibration. Oh well I will try the calibration again, I have put my other RAPT pill into the FV and it is reporting the SG correctly.

I want to put another batch in the ferment fridge tomorrow so I would like to have the pill reporting correctly for that batch.

[kmar92]

I re-calibrated my wireless charging converted pill and it now seems to be reading well. I left it in a bucket of water overnight and it was reporting consistently 0.999 - 1.001 and that sort of reflected some minor temperature changes in the bucket of water over 12 hours. It is now in a FV with my latest batch and it was within a couple of points of my hydrometer reading of the wort and really that is as close as you will ever get due to the errors in reading a hydrometer anyway (parallax error, cloudy wort making it hard to read, trying to read the bottom of the meniscus through the wort, etc). I will see how it goes during the ferment but I am confident that it is reading as accurately as I can get it to.

I must have buggered up the initial 2 point calibration. The RAPT pills are extremely sensitive as the accelerometer used will register the slightest change of angle. Anyway pretty happy so far.