I wonder, did anyone try this:
* Put your single dose low retention grinder on a scale. A big, sensitive one. Preferrably with a custom made "foot" the same size as the grinder base.
* Hook the scale up to the grinder so the grinder starts automatically on the desired weight and closes on 0.
* Tare the grinder (oops, that should not be necessary every time, the grinder could be tared once an then recalibrated). Pour coffee beans in.
* the grind cup or portafilter basket is suspended above the grinder on a separate stand so it and the beans don't affect the weight measurement.
* the grinder will start by itself whenever the correct weight is achieved, and stop exactly at 0, meaning you get exactly the desired weight in your cup, minus the grind retention, which in a low retention grinder should be pretty much the same every time, allowing you to dial in those extra 0.5g or whatever it might be.

This, in my mind, avoids the pre-grind measurement step and solves the problems with post-weighing the grinds dropping into the receptor with a scale hooked up to the motor: the impossible predictions of exactly how fast a particular bean/blend will grind, how much will stay in the grinding chamber or grinder chute. In "my" case, the grinder will not shut off until the scale is on 0, and that is when the entire weight has left the grinder, including the chute.

I know many sensitive scales appear very sluggish, which would mean they would react too slow to shut off in time - but isn't this a factor mostly of the extremely slow LCD displays employed on these scales? An LCD diaplay for showing weight in real-time wouldn't even be necessary in this case.

For me, something like this would be more interesting with a coffee roaster than a grinder.

aha, are you doing a lot of back to back roasting in small batches? Or are you suggesting that one could judge roast level by measuring weight loss during grind, and stop at the correct percentage?

The problem is in having a scale that can accurately weigh a 20-kilo grinder (or more) down to a 0.1 of a gram.

Much more realistic to accurately weigh the dose in a single-dose work flow, or to weight the portafilter and grind to weight, as with the 270w and some others.

The retention thing is really more about how much "stale" grinds have to come out before you get freshly ground material. If you have 20 grams of stale stuff in the chute and you push it out with 20 grams of fresh grind behind, you still have a basket full of stale coffee, albeit accurately weighed.

zix wrote:aha, are you doing a lot of back to back roasting in small batches? Or are you suggesting that one could judge roast level by measuring weight loss during grind, and stop at the correct percentage?

Basically as a way to log percentage weight lost through the roast as one more factor in determining the roast level.

Errm, am I mistaken or does that scale weigh post grinding? I am trying to describe pre-grind or inter-grind weighing. If the scale is indeed weighing the entire grinder except for the grinds receptacle can, then yes, it is more or less exactly what I am talking about.

The "problem" with post-grind weighing (I.e. weighing what drops down in the grind cup/can) is that many grinders have coffee coming down in clumps from the chute, or sometimes the last few bean grinds take a little longer to fall down. This could throw off the measurements with half a gram or more. Example: when the cut-off weight is reached, the grinder switches off and then another gram of coffee falls down through the chute. The user corrects by lowering the cut-off weight by one gram, and the next time, because of less static or something else, no extra gram of coffee falls down the chute after cut-off.

How does weighing the grinder prevent the problem you described.

yakster wrote:Basically as a way to log percentage weight lost through the roast as one more factor in determining the roast level.

Ah, I get it Sounds good to me.

nuketopia, yes you are right. If the grinder has a lot of retention, this method wouldn't work anyway. D'oh! Maybe I am just chasing windmills.

It would still be convenient not needing to weigh separately, and a weighing device coupled to the hopper or the grind cup/portafilter would suffice, in that case.