I need help setting up the Qwiic scale. I use the Qwiic scale NAU7802 together with a Arduino MKR 1310 and in principle everything works. However, I have one problem: Every time I restart the scale, the zero offset changes. I don’t mean just a little, but in the 50-60 gram range. For example, if it is 213500, the next time it is started it will be 130345, without I have changed anything. I’ve already tried a second Qwiic scale module, but it works the same way.
Once the scale has started, the offset remains constant over time, but is changing at the next start. That would mean that I have to calibrate the scale every time I start it. I think this is not the normal way this module works?
Can anyone help me, how can I stabilize the zero offset?
I checked the cables in the connector, they are stripped and tinned long enough, they should have good contact.
Not certain, but I’m pretty sure sparkfun’s example code stores the offset in EEPROM and then pulls that value back up at reboot. I’m not familiar with the MKR 1310 but it looks like it’s using a SAMD21 processor and those don’t have an EEPROM in them. What’s probably happening is the example code is attempting to retrieve the offset from memory but it’s not there and random numbers are coming back.
Many thanks for your response. You are right, the MKR has not the EEPROM but a 2 MB Flash memory.
But that’s not my problem right now. Example 1 which is the “Basic Readings” example , does not use the EEPROM and is just reading the zero offset. Based on this zero offset you can later calculate the calibration factor and store it in the memory.
Example 1 is also working well, but the problem is, that the zero offset is changing, when I turn it off and on again, or when I reset the Arduino. Sometimes it is relatively similar after restart, but an other time the value is complete different.
This would mean I have to tare the scale every time I switch it on, I think that shouldn’t be the case?
5-6% does seem a little high. Is there a time aspect? Does it seem to get worse when powered down for a while? Is the temperature reasonably stable? Given the zero shift, is the calibration otherwise maintained?
The room temperature is very stable at 23°C, I did not notice a time effect when powered down for a while, it seems to be randomly. However the readings are relativ stable, they change only slightly. Just the zero point is channged after every restart.