1

I'm trying to get a regular ph reading in an aquarium.

The sensor works well when the probe is in a small quantity of water(i.e. a glass) but has large variations in larger water quantities (i.e. aquarium).

The circuit uses an ads1115 and a node mcu.

I'm looking for suggestions on what i can do to reduce the interference. Here's what i've tried:

  • adding capacitors between gnd and vcc on the probe controller board.
  • different usb cables / power sources
  • unplugging all other electrical devices in the vecinity.
  • moving the cables around as to not intersect any power cables.
  • adding ferrite corea to both ends of the ph probe.
  • adding ground connection to the bnc connector.

Here's what it looks like and what values i get. The part where it stabilized is when i moved the probe to a glass of water in the same location.

enter image description here

enter image description here

enter image description here

gedorin
  • 21
  • 1
  • Show the pH graph of the glass of water and note that it is pH and Ph. Make sure the glass of water has the same temperature as the fish tank. – Andy aka Oct 12 '20 at 16:58
  • Does the sensor get adequate water flow ? Add a bubbler – Tony Stewart EE75 Oct 12 '20 at 17:02
  • Sorry for that spelling.. my bad. The graph is of both readings. Up to 19:12 the probe was in the aquarium. From 19:12, the probe was in a glass of the same aquarium water and same temperature. You can see the variation is much smaller and acceptable for my measuring needs. – gedorin Oct 12 '20 at 17:04
  • The sensor does get water flow while in the aquarium as oposed to the glass, but the unstable readings persist even with the aquarium pump unplugged. – gedorin Oct 12 '20 at 17:05
  • What is your SNR >10? Looks like <0. Search my answers for EMI solutions as this gets repetitive. For CM noise – Tony Stewart EE75 Oct 12 '20 at 17:10
  • Have you considered that different layers of water with different pH values are cyclically circulating? – Andy aka Oct 12 '20 at 17:36
  • Thanks for the input.. i'm in the process of looking through your answers but it will probably take a while as there are over 6k and no search feature. I appreciate the lead though. – gedorin Oct 12 '20 at 17:40
  • Andy, i have considered that. I did the test with the water pump off and for almost an hour (the water should have minimum movement at that point). I'm pretty sure it's interference and the large body of water acting like an antenna. I'm just not knowledgeable enough to fix it. – gedorin Oct 12 '20 at 17:42

0 Answers0