Pressure sensor values not consistent

Other Hardware Sensors
1

hi all, I have a pressur sensor as in the picture and I write the following code to read values with eps32 2432s028 shield.

#include "HX711.h"
const int DOUT_Pin = 27;   //sensor data pin
const int SCLK_Pin  = 22;   //sensor clock pin
HX711 pressure_sensor; 
void setup() {
	pressure_sensor.begin(DOUT_Pin, SCLK_Pin);
	pressure_sensor.set_scale(2280.f);
	pressure_sensor.tare();
}
void loop() {
  Serial.print("Pascal: ");
  pressure_sensor.power_up();
  Serial.println(pressure_sensor.get_units(),1);
}

unforunately I read always different value which encrease on its own from 830 to 840 Pa.
and then if I put tube inside a glass of water I don't obtain expected different pressure:

P = density * g * H = 1000Kg/m^3 * 0.1m * 9.81 m/s^2 = 981Pa
I obtain just 3Pa difference (passing from 830 to 833Pa and if I remove tube pressure the value remains to 833Pa and then encrease slowly on its own. Can someone help me to better use the pressure sensor?

sensor
sensor389×459 161 KB

2

How do you power the HX710.
It should be powered from VCC of the processor (3.3volt when used with an ESP).

This is a 40 KPa sensor, and might have a low resolution and drift a bit when used with those low pressures (<1KPa). A good airtight fitting hose is also important. And air slowly desolves in water...
Leo..

3

@sanga
What is the model of your sensor? Do you have a datasheet for it?

4

Hi, @sanga

What model is your sensor?

Is it an absolute pressure sensor or a gauge pressure sensor?

Thanks.. Tom.... :smiley: :+1: :coffee: :australia:

5

It's a 40KPa (0.4 Bar) gauge sensor, followed by a HX710, the stripped down version of the HX711.
No excitation voltage regulator, like a HX711 board has, so a bit more sensitive to supply noise.
I have helped another poster with a fuel tank sensor with this module, which seemed to work OK.
Leo..

6

Where did you get that number?

I see, it's from the example code and is totally meaningless for your sensor.

You need to do a calibration first.

7

many thanks for your reply

the article is ZkeeShop 3Pcs Barometric Pressure Sensor Module 3.3-5V Liquid Water Level Controller Board 0-40KPa

I took the scale value from a tutorial
many many thanks for your help

8

That number is for a particular weighing scale, totally meaningless for your pressure sensor.
To get meaningfull data from your sensor you need to do a calibration first.
Do you need help?

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