In a 1-wire network with multiple DS18B20s, I can read 400 DS18B20 data with expected results when the cable is 30m long. After adding another 200 meters on the bus, the temperature read is much higher than the actual temperature while the ROM ID of DS18B20 still returns the expected values. If the extension cable is removed, the measured temperature returns to normal. How do I solve this?

It is recommended to measure the resistance of the extension cable. If the cable resistance is too high, the voltage on DS18B20 will drop during temperature conversion. If this is the reason, please
1. Increase the strong pull-up voltage.
2. Replace the cable with a low impedance cable.

It is also possible to power the DS18B20 with an external power supply instead of parasitic power.