Throw-in Type Liquid Level Transmitter Spiking readings

I am experiencing some very unstable reading from the Throw-in Liquid level sensor, and have seen a few posts with similar problems, but no real resolution.

For the purpose of this post, I am reading the value from the Analog current to Voltage sensor using the ESP32 analogReadMilliVolts call. The code actually takes 60 readings 1 second apart and calculates the average on each loop (READER_SIZE == 60).

tank_value = 0;

for(u_int8_t count = 0; count < READER_SIZE; count++)

{

tank_read[count] = analogReadMilliVolts(A0);

tank_value += tank_read[count];

delay(1000);

}

uint32_t avg_value = tank_value / READER_SIZE;

During initial development I had a resistor and variable resistor connected instead of the Pressure sensor, set to give a range of current values equivalent to the Pressure sensor (1K to 2K Ohms with 24v). The readings I got were reasonable and fairly stable:

Once I connected the pressure sensor however, the readings became a lot more unstable (Same scale used here for comparison).

Looking a bit closer, the spikes seem to occur at fairly regular intervals of about 9-10 minutes apart.

Does anyone have any insight into this? I don't think it has anything to do with my code, or any RTOS background processing on the ESP32-C3 chip as I don't have any WiFi or Bluetooth etc enabled, and the previous runs of the code with the resistor network would rule out everything except the pressure sensor.

The fact that I am seeing a 15% difference on the readings even though I am taking 60 readings each time would also indicate that the pressure sensor is actually cycling through this range rather than just providing a single spike as this would be out of the range of the analog current to voltage sensor.

For reference, the sensor is sitting in a 4500l tank, which is about 80% full,. The water depth is about 1.5 meters, with the sensor near the bottom. If I move the sensor to just below the surface I get an adjusted reading as expected, but the spiking still persists.

This is my full loop() call:

void loop()

{

tank_value = 0;

for(u_int8_t count = 0; count < READER_SIZE; count++)

{

tank_read[count] = analogReadMilliVolts(A0);

tank_value += tank_read[count];

Serial.print("Analog Read: ");

Serial.println(tank_read[count]);

delay(1000);

}

uint32_t avg_value = tank_value / READER_SIZE;

Serial.print("Tank Level: ");

Serial.println(avg_value/41);

char cmd[13];

sprintf(cmd, "%02u%06u%03u%01u",

0x01,

avg_value,

avg_value / 41,

0x00);

lorawan->send(cmd, strlen(cmd));

}