Hi,

I purchased a DFRobot Gravity: Throw-in Type Liquid Level Transmitter in Australia from Core-electronics.

I am using a Wemos D1 Mini but have also tried using an Arduino Uno with the same results. The depth reported back is never stable. The water tank I am measuring is 1600mm tall and the sensor is at the bottom.

I have wired the Wemos and UNO the same as the example from DFROBOT's Wiki page at.

https://wiki.dfrobot.com/Throw-in_Type_Liquid_Level_Transmitter_SKU_KIT0139

The exception is the Wemos only has 1 analogue input at A0.

I have tried several power supplies from 12VDC switch mode plug packs to a 12VDC battery and then also building a 15vDC and 5VDC regulated power supply to power both the sensor and current to voltage converter and the Wemos or UNO boards. I have attached a schematic of this PSU.

I have also made sure that the sensor has been powered for at least 30 mins as I have read it needs to stablise. Also note if I pull the sensor slowly up out of the water the depth readings do change but 1. The level is no where near accurate and its still bounces all over the place.

Below is just a short list of the data read by the sensor to the Wemos. These are the depths in mm. You will see that they range from 573.75mm to 594.84mm. The water is still and not moving. The level has not changed at all. The tank is actually full at the moment so I would expect to see a level of around 1500 - 1600 mm.

581.34
587.25
592.31
581.34
592.31
589.78
576.28
576.28
576.28
592.31
581.34
565.31
592.31
573.75
567.84
587.25
594.84
581.34
576.28
578.81
589.78
587.25
560.25
587.25
578.81
584.72
584.72
567.84
567.84
467.44

What can I check. the code I am using for the UNO is below.

#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27,20,4); // set the LCD address to 0x27 for a 16 chars and 2 line display

//Definitions

#define ANALOG_PIN A2

#define RANGE 5000 // Depth measuring range 5000mm (for water)

#define VREF 5000 // ADC's reference voltage on your Arduino,typical value:5000mV

#define CURRENT_INIT 4.00 // Current @ 0mm (uint: mA)

#define DENSITY_WATER 1 // Pure water density normalized to 1

#define DENSITY_GASOLINE 0.74 // Gasoline density

#define PRINT_INTERVAL 1000

//Variables

int16_t dataVoltage;

float dataCurrent, depth; //unit:mA

unsigned long timepoint_measure;

unsigned long delayTime;

void setup()

{

Serial.begin(9600); //Start serial port

delay(2000);

Serial.println("Started App");

delay(100);

delayTime = 30000; //get depth readings every 30 seconds

lcd.init(); // initialize the lcd

// Print a message to the LCD.

}

void loop()

{

GetDepth();

lcd.backlight();

lcd.setCursor(0,0);

lcd.print("Depth:");

lcd.setCursor(10,0);

lcd.print(depth);

lcd.setCursor(0,1);

lcd.print("Voltage:");

lcd.setCursor(10,1);

lcd.print(dataVoltage);

lcd.setCursor(0,2);

lcd.print("Current:");

lcd.setCursor(10,2);

lcd.print(dataCurrent);

delay(delayTime);

}

void GetDepth(){

if (millis() - timepoint_measure > PRINT_INTERVAL) {

timepoint_measure = millis();

dataVoltage = analogRead(ANALOG_PIN)/ 1024.0 * VREF;

dataCurrent = dataVoltage / 120.0; //Sense Resistor:120ohm

depth = (dataCurrent - CURRENT_INIT) * (RANGE/ DENSITY_WATER / 16.0); //Calculate depth from current readings

if (depth < 0)

{

depth = 0.0;

}

}

}

This is just sending the data every 30 seconds to a LCD display and it is bouncing all over the place.

I am 100% positive the power is very stable.

What else can I try.

I have tried using ultra sonic sensor for getting the tank water level and also using TOF laser sensors. The problem with both these is that they tend to get false readings from the sides of the tank. I was hoping that this pressure sensor would be accurate but alas I think I have wasted $90.

Regards

Richard.