Perfectly Calibrating Decent Flow Measurements
The DE1 firmware has a physics model of the pump we use, which allow it very closely estimate the flow rate. It's much more accurate than a standard flow meter, which typically can't handle flow rates under 2 ml/s. And the latency is much better, being able to notice very quick transitions, such as a channel opening and closing in a coffee puck.
But our approach has one big weakness. The pumps we use behave very differently if the electrical voltage and frequency is not what we expected. That's why, in the de1app, there's a settings->machine->calibration setting for “Flow”.
If you own a bluetooth scale, you can use that to perfectly calibrate your DE1, and many people have done that.
However, I've been really not happy with a few extreme cases, where our default calibration is way off:
- South Korea and USA when running 240V, with its unusual electrical frequency of 60hz in the 220/240 range.
- Japan, with 100V and two different frequencies, of East vs West Japan
- customers have to be told to recalibrate their machines, or else the flow measurements are really wrong.
I've not been happy with that, but hadn't seen a obvious solution.
Last week, it occured to me that we could calibrate our machines for the two most common cases: USA and EU, and for all other countries, we could recalibrate that person's machine to the country where that machine is being shipped.
The downside is that this can delay shipping their DE1 by up to a day, but I think it's worth it so that customers who don't recalibrate (in the current system) don't have a less-perfect experience.
It also occured to me that I could find a table of combination of voltage and frequency in the world, we could build a calibration table for all those countries, and this would massively speed up our work.
I also decided that when a machine is going to a country that isn't the default voltage/frequency, that I'd print on the invoice itself, in yellow type, the suggested flow calibration. We'll do it for you, but you've got it in writing too.
More importantly, my boxing team can see the bright yellow print, and knows to hand that machine back to an engineer, to recalibrate for that person's country.
I'm a bit embarrassed that it's taken me so long to figure out how to solve this calibration question. Sometimes a problem just has to percolate in our brains for a long time, before an obvious solution surfaces.
I've also posted an updated page in the Decent manual “Voltages, Frequency and Default Calibration for every country” so that if you don't own a bluetooth scale, and you already own a Decent, you can enter the newly calculated optimum default calibration for your country.
-john
#calibration #firmware #factory
Updated 2021/12/23