Who wants to build and sell varios for a french company?

[Erni]

It is my understanding that it is stable for each chip, which also are explained in the article I mentioned.
Also it has been discussed numeros times on the Arduino forum, but I could make a test (put a Arduino in the fridge )
So just calibrate once pr chip and you are done.

[mstrens]

It is my understanding that it is stable for each chip, which also are explained in the article I mentioned.
Also it has been discussed numeros times on the Arduino forum, but I could make a test (put a Arduino in the fridge )
So just calibrate once pr chip and you are done.

Erni,
If you make the test with the fridge, could you also make a test to see if it remains stable when the voltage on raw pin varies from 6 volt down to about 4 volt. Some people are using the arduino with a Nimh 4.8 nominal and when the voltage drop below 5.x volt, the voltage regulator can not regulate anymore and Vcc on the chip goes down.

There are even people using it with a lipo cell (so with perhaps 3.5 volt and out of tolerance)

[Erni]

So the result of my fridge test.
I calibrated at room temp. whish is 28 degree C and the voltage was 5.03V.
In the fridge at 5 degree 5.05 V and in the freezer at -18 degree 5.07.

I then tried to lower the voltage from 5V to 3.3 V om the Vcc pin, and the reading was 3.26V, my voltmeter showed 3.27V

[MikeB]

But you still need to do a calibration on every unit. An accurate, external reference avoids this.
This calibration might not matter when only a very small number are produced, but if a sizeable production run is done it is very time consuming.

Always better to be "accurate by design" then to need "select on test"/"calibrate".

Mike.

[mstrens]

But you still need to do a calibration on every unit. An accurate, external reference avoids this.
This calibration might not matter when only a very small number are produced, but if a sizeable production run is done it is very time consuming.

Always better to be "accurate by design" then to need "select on test"/"calibrate".

Mike.

You are right for a production unit but I do not think that the idea is to produce large quantities of OXS.
Calibration also allows to take care of tolerances (e.g. on resistors, non linearity effect, ...).

It seems me acceptable for a project like OXS in order to keep user complexity (soldering, ...) as low as possible.