ADS1115 unstable measurements

connecting all 4 inputs to 3.3v i get these charts.

I don’t know why these measures are unstable.
i really need this a/d for connecting ec-ph modules and hall effect current sensor.
3.3v supply is stable, 5v fluctuates to 4.55 from 4.62.
I used both supply voltage for test.

Can you show me a graph of several measurements when connected to a battery?

I connected an old 5v usb battery
to raspberry but nothing changed.
Output from battery 4.98V - 5.03V
Output from raspberry (4.42V - 4.63V) and 3.28V stable.
Trying to supply ADS1115 with 3.3v, measures remains unstable.

There are a lot of things that can cause what you’re observing. It appears to be operating normally after seeing the accuracy when connected to a battery, so it is likely your power supply that is the issue. 4.6 V is also an insufficient voltage to power a Pi. Additionally, the circuit you’re using the ADS1115 in can have a significant effect on noise (e.g. does the circuit have ferrites?). Last, the number of measurements you have set to average also affects the ability of the software to smooth outlier measurements.

I have 3A 5V power supply and voltage is stable.
4.6V is the voltage in gpio pin for supply the ADS1115.
Stabilizer inside Raspberry lowers the voltage.
I found the problem right now.
i need two input modules for using your new PH/EC read function and at the same time use the remains two input for other purposes.
But clearly that’s not possible.
So, deactivating one of two modules, measurements become stable.
Do i need to buy another ADS1115?

You can create a new Input with pH/EC measurements and voltage from the other 2 channels. Open each Input to learn how they both work and take the relevant parts from each. Import your new Input and you’re good to go.

The problem is exactly this.
I am already using two inputs for the same ADS1115 and this cause conflicts.
If you integrate all 4 ADS inputs in PH/EC would be better, i think.
But i can solve it by using another ADS.
it also not possible set the number of measurements to average in PH/EC inputs.
I have another big problem, i don’t know if i should open a new post for this.
Using PH/EC input i can’t calibrate the probes.
Here is the voltages…
I don’t know, is it normal?

SKU SEN0244 EC sensor module

200 - 0.4V
1400 - 2V
4300 - 2.3V

PH4502C PH sensor module

7 - 3.0V
6 - 3.1V
4 - 3.5V

All the more reason to create a custom Input like I suggested.

Why not?

maybe i didn’t understand what you said to me.

after calibrating PH4 and PH7, if i measure PH6, this is totally out of range.
Same thing for EC
i think this is another reason to create the custom inputs that i didn’t understand.
Could you explain to me?
Do you talking about rescale method with equation?

As far as I know, the calibration works. This module was created recently and I know of no issue with it. Perhaps you’re not calibrating properly.

You would create a custom Input to be able to do all the things you mentioned (measure pH, EC, and the remaining 2 voltages).

Here’s the thread where the ADS1115 pH/EC Input was created:

Just jumping in here. This part number appears to be for a TDS probe, not an EC probe. I know the working principles are similar, but without knowing exactly how this TDS sensor board is designed it’s hard to know what is going on. In the EC probe that I used to prototype the pH/EC custom input, the EC sensor board perturbs the pH measurement and must be modified to filter out the galvanic offset. I made a post about it on the old forum here.

Not sure what this means. Are you trying to power ADS1115 from the Raspberry Pi GPIO pin?

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Now i understand.
I tried to import ads1115_analog_ph_ec.
I was hoping for this feature, but ther’s too much to learn.
I need time.

working principles is the same, diference is just a conversion.

I will try to use your script, but before i need to understand what you have done, because, as i said, python is new to me.
And i need to learn more about mycodo.
So, i’m sorry to proceed slowly.

Sorry, 5v pins, no gpio

You can do an experiment without bothering with Custom Inputs. Just set it up as a regular ADS1115 as you have done.

  1. Connect both pH and TDS probes to their sensor boards, and connect each sensor board output to two channels on the ADS1115.
  2. Make a voltage measurement of the pH sensor output with the pH probe only inserted into the solution. Do not insert the TDS probe into the solution. Note this voltage.
  3. Now insert the TDS probe into the solution, and see if the pH sensor voltage changes.

If the pH sensor voltage changes when the TDS probe is inserted, then you are seeing galvanic effects from the TDS probe. You will need to solve this first.