I'm trying to connect an ACS712 current sensor to an ESP32 ADC pin. The ESP32 expects 3.3 V, but the ACS712 can reach 4.5 V.
When there's no current going through the ACS712, its signal is 2.5 V, so I made a test: I made a voltage divider using 330 Ω / 1 kΩ resistors and instead of the 2.5 V dropping to 1.88 V as expected, it dropped to something like 0.4 V.
As soon as I connect the 1 kΩ between signal and ground, the signal drops from 2.5 V to 0.4 V.
Using much bigger resistors (4.7 kΩ / 10 kΩ) it works as expected, but I'm left wondering why it doesn't with smaller resistors.