AssafL wrote:Do you flush before the first pull? It may be that there is some extra volume in the pipe that fill up?
If it sometimes happens in reverse (first being 45 and the second being 39) then obviously this isn't it. But if it always goes up - it may be that.
BTW. This is a >10% error. It should be within a gram (even less). So there is something wrong.
You can connect to the flow meter with a scope or an Arduino and count the pulses. See if during the pull pulses are missing and at what point in the pull.
You can also pull the cap off the flowmeter (if it is a gicar) and see if the is debris or something clogging the nozzle. If you do don't bend the tabs - if they break it is an expensive part.
So this morning it actually happened the opposite. I woke up to a warm machine, did not flush. First pull was 40g. Second pull was 45g.....very annoying. But yes to answer your question, I have tried different flush cycles to try narrow things down.
One thing I have noticed is that if I flush inbetween shots (to rinse coffee from the shower screen) at a low pressure, my next volumetric shot can be out as much as 15g under weight. It almost seems like air is passing the flow meter and giving it inaccurate readings. I can tell when a shot will do this instantly. Depending on my dose and basket used, it usually takes about 24ml to fill my portafilter. So essentially my flow meter on the screen will quickly fill to 24ml, after a few seconds I'll get some coffee dripping and slowly the ml will climb up to my desired volume and my shot will finish pretty close to my desired weight. If I flush with a low pressure and repeat my profiled shot, the basket with fill with upwards of 50ml of water and my resulting shot will be 10-20 under my desired weight. To alleviate this I've been making sure to flush with a higher pressure. Doing that gets me around +/- 5g of my desired weight.
My last response from Rocket was that this is the same flow meter set up used in several different brands of espresso machines and that my error is consistency is "industry standard" and not isolated to the R Nine One. Can any GS3 AV owners chime in on this?
I have replied to Rocket and they are currently looking into things...