"Zero" tracking on the Acaia scale for coffee

[More photos and videos about the acaia lunar here]

Mr Rex Tseng from Acaia explained some details to me about the "zero tracking" mechanism in their scales.

Initially I had no idea what this was about. One assumes that a scale shows the weight, period. For coffee, one ideally wants a scale with 0.1g precision so the optional 0.01g resolution of the Lunar is especially pleasant.

If there is no weight on the scale and it displays 0.00g then a number of circumstances can give the scale the impression there's some minute weight on or off it. At this rate of sensitivity, even blowing your nose near to the scale can make the scale sense the air movement and translate this into a temporary "weight".

But even though one wants the scale to ignore such tiny differences at 0.00g it is still necessary to display all minute changes when one is actually weighing off something. For instance, when measuring off an exact 14.00g of dose into a filter basket, one does want to see the numbers reflect the tiniest pinch of extra grinds added or taken off the dose.


The video above shows my checking this out and below is a quote from the message by Rex Tseng:


The tracking option in the settings menu is a technology for acaia scales to remain stable at zero. 

Here are some backgrounds of the weighing definitions:

min = minimum starting weight
d = minimum increment of the scale
max = maximum weighing capacity
e = margin of error

for the acaia Pearl (1.74)
min = 0.3g
d = 0.1g
max = 2000g


For all the scales / balances, the weighing result will drift over time due to many different reasons. The ‘zero’ point (0.0g) will drift, especially over a span of time. It could be heating from the electronics, can be the ambient noise, can be the room temperature changes, or simply because of a cheap / poor load cell sensor.

The zero tracking mechanism in acaia is designed so that it will track the zero point within certain criteria to allow the zero point to remain stable over the time span. For example, 

When the zero tracking range is set at 2d (2*0.1g = 0.2g) in the option menu:

If the zero point drifts from 0.0g to 0.1g (it can be a drift or putting a weight of 0.1g on the Pearl), it will be ‘tracked’ and the scale will read 0.0g. 

If the zero point drifts from 0.0g to 0.3g (it can be a weight of 0.3g on the Pearl), it will not be tracked and deemed as an object on the Pearl. 

This zero tracking allow the Pearl to perform long time consistency for the starting zero point. 

The zero tracking mechanism will NOT operate if there is any weight on top of it, it only operates around 0.0g. So if you put a 10g weight on the Pearl, and add 0.2g on the Pearl, it will show 10.2g. 

If you try with other low-end scale in the market, you will notice that if you turn on the scale for period of time without weighing, it will read from 0.0g to any numbers like +- 0.5. That’s also one reason low-end scales need to have an auto off set at 1 minute, in order not to show its unstableness. Another reason for low-end scale to set the min = 2g  (even though d=0.1g), is also because they were not able track the zero point, so they will ignore anything below 2g at zero point. 

So if you want to see the most responsive weighing result, you can make the zero tracking to 1d or OFF, the trade off will be a less stable zero point.