Unstable ph value

Hi guys
I have a problem with my ph module diymore hc4502
When i test the output of the module with a multimeter i get a stable value
For exmple ( ph 7 = 2.5 volt)
But when i use analog read of arduino iget unstable reading .The value changes between 2.4 and 2.6
Any solution to fix this problem ?
Thanx for replaying

What does the specification, the data sheet, promise?
Schematcics please. Decoupling caps used?

My guess is that there is noise on top of the required signal. When you measure with a multimeter there is some averaging done by the meter, which gives you a steady reading. When you take a reading from the Arduino it is more of an instantaneous measurement so it will vary depending on the noise.

What happens if you take multiple readings, and calculate the average?

Only when you supply the circuit, the code, and some perfectly focused photos. :roll_eyes:

When an ADC takes a reading, there is often a bobble of 1 LSD because of the timing of the conversion. When you convert that reading to a voltage, there may be round off error of 1 LSD.

We don't know which Arduino you have, how you have connected things, how you have powered it, and if you use default Aref (bad idea) for those voltage measurements.
If you want help, then give us all the details.
Read the "how to post" guidelines first.
Leo..