My Sanken Solar Water Heater Controller is faulty, so I am trying to design a new, improved controller using Arduino, ESP32, or Raspberry Pi. However, I need help understanding how the sensor transmits two different types of data — water level (indicated at 25%, 50%, 75%, and 100%) and temperature (in the 0–100 °C integer range) — using only two wires (i.e., a 2-core cable).

I have already tested the sensor using my oscilloscope to analyze the waveform. The sensor outputs a square wave with a pulse count of 25–28 at a temperature of 25 °C. The peak-to-peak voltage (Vpp) varies with water level: Vpp = 8 V at 0% and Vpp = 3.92 V at 100%. Unfortunately, I cannot get valid readings at 50% and 75% due to a fault, but I am confident that the 0% and 100% readings are accurate.

Here are the sensor: https://www.google.com/url?sa=i&url...ved=0CBQQjRxqFwoTCNDK882zno0DFQAAAAAdAAAAABBU

 

The scope photos show a burst of pulses for about 550ms.
How often do these bursts occur?

It would appear the number of pulses in a burst indicates the temperature in degrees C, and the amplitude indicates the water level.

So what about doing an A/D conversion of the pulses with a micro, and then analyze that in software to get the pulse height and pulse count?

 

i tried that, but the sensor literally just a probe without internal ADC, it seems the original controller somehow generate the pulse count automatically. So the original sensor only change indutance, capacitance, or resistance based on temperature and water level (the water level detected by the iron beads with black silicon jacked). Can you give me any idea how it probably coded it

 

So the original sensor only change indutance, capacitance, or resistance based on temperature and water level

Can't help you without knowing what the sensor output change is for the variation of temperature and water level.