We have a strange behavior with different ADT7420-Sensors. We had 4 Sensors on a i2c-bus and everything works fine at roomtemperature. We can make good measurements. We can switch off and on the powersupply and everything works as expected.
If we increase the temperature to 115°C, everything works fine again.
But if we switch off the powersupply at 115°C and then switch on again, some sensors measure 0°C. We can switch off/on repeatedly, but 1 of 4 sensors measure allways 0°C. The i2c-communication with this sensor is ok, but the temperature-data is 0. We have this behavior with 2 of totally 7 sensors.
The only thing we can do is: cool down to ca. 70°C, switch off/on and then the sensor works again. Or we can send a software-reset over i2c, after this, the sensor works again.
We plan to use 1500 of this sensors in a testing-machine at temperatures from -40°C to 115°C. So we need to know what is wrong with our circuit or with the sensor. Can you please help us?