Dumb iSpindel Question(s)

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Oct 24, 2018
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Netley Abbey, Southampton
Hello, I purchased a replacement battery from CPC Farnell for my iSpindel (I gave up on my previous order after all my attempts at communication disappeared into a black hole) - I now have a couple of questions.

First dumb question: How do I change the battery? I take the top off the iSpindel but it seems thoropughly wedged in to the tube. There's a bit of the PCB protruding on the opposite side from the two calibration points, and I can just get a pair of needle-nosed pliers onto it, but I hesitate to pull too hard in case I break it. I've owned the iSpindel for two and a bit years, it hasn't leaked to my knowledge - could the PCB have jammed?
[ Update: I got it out. I was able to just nip the PCB with my pliers and then lever them using the edge of the tube as a fulcrum to ease the PCB up a millimeter at a time.]

Second half-dumb question: assuming I manage to get the PCB out and the battery swapped, I assume I will have to recalibrate it - is that correct? I purchased it ready-calibrated from a vendor on this forum, so I've never done the process. Is there an idiot-proof step by step guide I can follow (preferably a written one, not a YouTube video) to get it giving accurate readings?

The iSpindel does already have my home WiFi and a connection to a BrewSpy account set up so hopefully I won't need to re-configure those.
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Battery should be pretty standard weight so may not need calibrating. If you stick it in water and it reads 1.000 then you're good.

Otherwise, first you'll need to note the angle of the iSpindel in plain water. Then you'll need to put it in a sugar solution at the higher end of what you brew at (e.g. 1.060 or 1.080), measure the gravity with an actual hydrometer/refractometer and note the angle of the iSpindel in the UI. Dilute the sugar solution by a third and repeat, and then again.

You can put that into the Excel sheet here to get your polynomial: https://www.ispindel.de/docs/Calibration_en.html

Another way to calibrate it is to stick it in a fermenting beer and take hydrometer samples every few hours alongside the iSpindel angles.
In the mode where you connect to the ispindel you could float the ispindel in water and make a note of the angle, then when you set the PCB back in check it again. If the PCB is a tight fit in the pestle then you can slide it out a bit to make are the angle after the battery change is the same as the angle before.

Ultimately no matter how well you calibrate it its irrelevant as you cant get an accurate reading so best to just monitor the trend rather than the actual number so then calibration doesn't matter.
Well, I put the new battery in, turned it on and left it in a pan of plain water and it's givern reads of 0.996-0.998 overnight so I'm good with that for now. I've dropped it in a recent brew and will compare what it says with the measured FG when it stops changing. If that's close enough then that will do me.
That sounds close enough. I did a similar thing with mine recently. As Scotty says, it'll never be completely accurate so just use it as a guide for when fermentation is over (slope of graph rather than actual figures).

Over the course of the next few brews, keep a note of the tilt angle at start and end of fermentation, along with your hydrometer reading. After 2-3 brews, you should have enough readings to use to calibrate it again (by plugging the numbers into the online tool).
Thanks for the caution @RoomWithABrew, I'll check when I get the iSpindel out of the brew. It is waking up and sending every 3 hours at present so I presume it's not got flooded but I'll confirm the tube integrity.

Something odd, though. Friday night I changed the battery, put the iSpindel in plain water overnight. Got 12 hours of readings ~0.997, transferred unit into a brew that was ongoing (Bulldog Premium IPA kit, started Monday 8th) - this brew looks close to done, is just glugging pretty slowly. The reading values are almost exactly the same! I have to assume that either (a) the IPA FG is truly 0.997 (seems highly unlikely) or (b) the float mechanism is stuck and producing a 0.997 reading regardless.
I'll leave it in the brew until I bottle in about a week, and do some more tests then.

2024-04-14 10:55 22.44°C 0.9971 IPA just now
2024-04-14 07:57 22.56°C 0.9971
2024-04-14 05:00 22.69°C 0.9973
2024-04-14 02:03 22.88°C 0.9974
2024-04-13 23:06 23.00°C 0.9973
2024-04-13 20:09 23.00°C 0.9975
2024-04-13 17:11 23.00°C 0.9978
2024-04-13 14:14 23.12°C 0.9979 IPA
2024-04-13 11:17 23.12°C 0.9984 IPA
2024-04-13 08:19 19.88°C 0.9956 water
2024-04-13 05:22 20.94°C 0.9967 water
2024-04-13 02:24 22.56°C 0.9977 water
2024-04-12 23:28 25.75°C 0.9984 water
2024-04-12 20:31 32.12°C 0.9984 into plain water
Can you see the angle on your software? Is that changing?
If the new battery is heavier then ispindel floats more vertical. Might not be able to float towards horizontal in denser wort.
However normally you'd find your reading would go lower and lower as gravity fell.
When it comes out check edge for damage then set horizontal ( 90 degrees ) in calibration. Then test in water angle should be 20 to 25 degrees.
Then try a denser fluid ie sugar and water and compare to hydrometer reading.
I don't get the angle in the 'raw data' table (on BrewSpy) but I can see the tilt angle in the popup data for each point on its chart. That is only available from 2024-04-13 11:17 onwards - it seems to show that we are getting a tilt variation consistent with the gravity numbers. I'll have to try some test reads with water as you say. I did do the horizontal calibration step after fitting the battery.

2024-04-14 10:55 22.44°C 0.9971 21.97
2024-04-14 07:57 22.56°C 0.9971 21.97
2024-04-14 05:00 22.69°C 0.9973 22.02
2024-04-14 02:03 22.88°C 0.9974 22.09
2024-04-13 23:06 23.00°C 0.9973 22.05
2024-04-13 20:09 23.00°C 0.9975 22.13
2024-04-13 17:11 23.00°C 0.9978 22.3
2024-04-13 14:14 23.12°C 0.9979 22.33
2024-04-13 11:17 23.12°C 0.9984 22.56
Touch the raw data field you see the angle.

You can share the brewspy ferment use the share icon in red top right or in the row of green icons above graph.

Can you see yeast all over the lid of iSpindel ? That can skew the reading, but not by much and won't affect a trend.

I used this video to calibrate and took notes as I watched it before trying the process.

I took a sample of the current ferment around day 4 when ispindel said 1.018 and it was really 1.020 with my corrected refractometer reading. Beer was at 12 psi and then I raised temp and pressure rise to 25 psi before cold crashing and it's stable now. I'm unable to check the FG as in UK.
Did your ispindel go in at the beginning of ferment?


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Touch the raw data field you see the angle.
View attachment 98282
Brilliant!! I never knew that! Thanks!
You can share the brewspy ferment use the share icon in red top right or in the row of green icons above graph.
View attachment 98283
Sure can! This link is valid for 6 hours only, till just before 1a.m. Thursday. PM me and I can generate another as required -

Can you see yeast all over the lid of iSpindel ? That can skew the reading, but not by much and won't affect a trend.

Dunno. I have not opened the FV ( it's in a low level corner cupboard, and a narrow 4-inch screw-top vessel)
I used this video to calibrate and took notes as I watched it before trying the process.

I watched the same one, but did not go through the full procedure. I was a bit put off by the fact he used a refractometer which I am not very familiar with how to do the correction for. (Poor grammar. Stay behind and see me!) Also felt that as it had read 0.997 overnight in water it was close enough to use as is for the first trial.

I took a sample of the current ferment around day 4 when ispindel said 1.018 and it was really 1.020 with my corrected refractometer reading. Beer was at 12 psi and then I raised temp and pressure rise to 25 psi before cold crashing and it's stable now. I'm unable to check the FG as in UK.
Did your ispindel go in at the beginning of ferment?

No, the brew was already under way for 4 days so quite advanced (only glugging very slowly) so I imagine pretty near done and I would expect ~1012 maybe. I plan to take a reading when I bottle in a few days time.
@hoppyscotty speaks the truth of course. These devices are never bang on and you can go mad trying to get them that way. I have found they are right on the OG or the FG, but never both! I have used the online tool to tweak the calibration from actual readings which improved it somewhat. My advice is to take the OG with a conventional hydrometer and overwrite the iSpindel's OG if necessary in Brewspy. Then follow the downward trend and take the second conventional reading when the iSpindel's curve has been flat as a pancake for at least two days. You will then a) be confident that fermentation has finished and b) will be able to calculate the true ABV and c) enjoy drinking beer.
Agreed with above, i have one ispindel I use for wine ferments. It's bang on with OG and final.
But wine ferment is so different to beer, no krausen, no pressure.
My Other iSpindels in beer show trend perfectly and if I'm really needing a reading I take a sample closed and use the refractometer.
@Victor Churchill
I use my hydrometer when calibrating, do remember to rinse and wipe it between readings as high gravity syrup clings onto it.
I decanted some syrup and diluted each time rather than making gallons of dilute sugar solution during calibration. i could do all the calibration readings in a large jug that way.
Use the sugar solution in a beer afterwards or make some invert.
My first ispindel I calibrated iaw the YouTube video above. It was a bit of a messy PITA, but I soldiered on and completed the calibration. However since I've used it in real life it has never ever agreed with the actual gravity of my fermenting beer. Occasionally the error will narrow such that at final gravity it'll only be a point or so out or sometimes bob on vs. the hydrometer. However when I test it in a sugar solution it always measures bob on to the hydrometer and refractometer readings, so my initial calibration still seems to be valid, so its not the calibration that is causing the error.

The problem clearly is the accumulation of krausen on the iSpindle pestle and lid...this is a very sensitive instrument so a small amount of Krause stuck to the lid or the rim around the lid will affect the reading. It seems impossible to me to prevent this from happening with this style of floating hydrometer. Other devices such as the Kegland pill and the Tilt look to be slightly better designs as they are smooth sided and probably don't accumulate Krausen as readily, but I'd be surprised if they are completely immune from this issue. And they come with other disadvantages like cost and limitation of connection features etc. so pound for pound the iSpindels are the best option and pretty unbeatable from a cost/performance/quality point of view, so better to embrace the limitations of such a device and just accommodate it.

Therefore since I have always bought ready calibrated iSpindels and just monitored the trend. It seem a waste of time to try to get it in some way to read accurately. I've sometimes pondered grinding off the protruding lip at the base of the lid which is good at accumulating Krausen and maybe even smoothing off the sides of the lid...but all seems like too much faff to still end up with an imprecise instrument.

Maybe if it could float a couple of inches below the surface of the beer under the Krausen, then it might work better, but not sure how you'd tune it to achieve neutral bouyancy just below the surface. Would probably end up with an extremely complex and expensive device.

I like the look of the Plaato device but it's expensive and, last time I looked at least, seemed to attract alot of disappointed and disgruntled customer feedback, so not sure how well it actually worked. And they went bust, but I've recently been bombarded with adverts for them on social media so maybe they're back in business?
I've had the same experience. Bang on with sugar water, but it's rarely accurate in wort. It's a shame, but I can rectify that with start/end hydrometer readings. I'm more interested in it to understand fermentation activity.
You'll never stop yeast sticking to a spindle/tilt/pill.

Even the smooth sides under the surface have yeast build up on them (you can see this when you pull out out)
The floating gravity monitors all have the same problems.
The ispindel shows the trend and temp well.
An ispindel that had buoyancy below the surface would be challenging to design, especially with the changing density.
Plus getting a WiFi signal out from below liquid would be tricky.
If you want to count bubbles

But this is no good for pressure fermentation.

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