PH reading low

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Sebyte

PH reading low

Post by Sebyte »

I have been out of the country for the past month and have used the portal to monitor the tank. I noticed around three weeks ago the the PH was dropping every day. I got my son to go over and check the PH using an API kit and the PH was within the normal range for the tank.

Over the next three weeks it dropped to 5.3. I have now taken a look at the problem, and have found that if I remove the ATO connection from ATO1 then the reading goes up to 6.13, but no higher.

I have cleaned the probe without effect, but I cannot get any calibration fluid until the weekend, I am not sure it is a calibration issue anyway.

The questions are, is it an interference or connection issue with the ATO circuit, or is my probe faulty?

And how do I resolve it?
rimai
Posts: 12881
Joined: Fri Mar 18, 2011 6:47 pm

Re: PH reading low

Post by rimai »

It could be stray voltage from the float switch.
It definitely has some interference by what you just described.
So, the first thing would be to replace the float switch.
It could also be stray voltage from one of your pumps.
What ph value do you get when you place the probe in a cup of tank water?
Roberto.
Sebyte

Re: PH reading low

Post by Sebyte »

I disconnected the extension lead to the probe and plugged it direct into the RA head unit. Placed the probe in a glass of tank water and after one hour the reading was 6.4.

It looks like the probe to me.
Sebyte

Re: PH reading low

Post by Sebyte »

The reading is the same in tap water.
rimai
Posts: 12881
Joined: Fri Mar 18, 2011 6:47 pm

Re: PH reading low

Post by rimai »

What numbers do you get when you load this code:

Code: Select all

#include <Salinity.h>
#include <ReefAngel_Features.h>
#include <Globals.h>
#include <RA_Wifi.h>
#include <Wire.h>
#include <OneWire.h>
#include <Time.h>
#include <DS1307RTC.h>
#include <InternalEEPROM.h>
#include <RA_NokiaLCD.h>
#include <RA_ATO.h>
#include <RA_Joystick.h>
#include <LED.h>
#include <RA_TempSensor.h>
#include <Relay.h>
#include <RA_PWM.h>
#include <Timer.h>
#include <Memory.h>
#include <InternalEEPROM.h>
#include <RA_Colors.h>
#include <RA_CustomColors.h>
#include <RF.h>
#include <IO.h>
#include <PH.h>
#include <ORP.h>
#include <AI.h>
#include <ReefAngel.h>

void setup()
{
  ReefAngel.Init();  
}

void loop()
{
  ReefAngel.LCD.DrawText(0,255,10,10,ReefAngel.PHMin);
  ReefAngel.LCD.DrawText(0,255,10,20,ReefAngel.PHMax);
  ReefAngel.LCD.DrawText(0,255,10,30,ReefAngel.Params.PH);
  ReefAngel.LCD.DrawText(0,255,10,40,analogRead(PHPin));
  ReefAngel.Refresh();
}
Roberto.
Sebyte

Re: PH reading low

Post by Sebyte »

Roberto here are the results from your test code.

Probe in cup of tank water

540
830
628
470

Probe in tank

540
830
648
490

Probe in cop of RODI water

548
830
695
539

PH tested at 8.1 using API kit
rimai
Posts: 12881
Joined: Fri Mar 18, 2011 6:47 pm

Re: PH reading low

Post by rimai »

Looks like the probe is no good anymore.
You can't really measure pH on RODI, both tap and tank look too low.
Did you leave in vinegar for a couple days when you said you cleaned??
Roberto.
Sebyte

Re: PH reading low

Post by Sebyte »

No I did not do a long soak, but I will give it a try now, and give it a good two days.

If that does not work I will order a new one, there are a few other bits I want as well.

Many thanks
Sebyte

Re: PH reading low

Post by Sebyte »

I replaced the probe and after several attempts to get it calibrated it worked OK for about three weeks.

It has once again started to gibe bad readings. My test shows a PH of 8.2 and the new probe 6.3.

I am beginning to thing it is due to stray voltages from the ATO switches. So I have just order the new water level expansion unit to see if that helps.
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