[APD] odd Pinpoint controller

[Cavan <millsman7 at yahoo_com>]

Hi all.  

I seem to be having a few problems with my Pinpoint pH
controller.  It seemed to be working fine for the
first two months or so, but...  

When I look at the display, the reading will jump
suddenly from say, 6.65 to 6.70 instantly (bigger
jumps than the first two months).  And back down.  It
switches the solenoid on and off a bit too much.  I
came back from vacation to an algae farm.  The pH is
supposed to range from 6.6 to 6.7.  Looking at the
tank, it sure doesn't look like there's really enough
co2 in there, even though the controller says there
is.  I suspect that the tank didn't get very good care
during my absence, but that's another story...    

When I tested the pH with my Lamotte low range kit
(6-7.4), it looked more like 6.9 (KH is 4) and not the
6.7 on the LCD.  The controller is off by .2?  Later
on I got the same 6.9 reading with the kit when it
said 6.6.      

Here's the weird part.  I just calibrated it last week
after about two months and it was right on the money. 
I used to have a monitor only that wouldn't work when
the lights were on (PC and T8).  The reading would
jump all over the place.  I put in a grounding probe
and it worked fine.  For a while.  Then it started
acting funny too and just kind of seemed a bit "off" (
I think the probe died prematurely).    

The PC is grounded and a believe the T8 is as well
(maybe not, but I can just turn that fixture off and
get the same results).  

Though the monitor did not work at all without the
probe, it doesn't seem to make any difference with the
controller (I will probably use it for a reef in the
future) for some reason.  Touching the grounding probe
to the PC reflector doesn't produce any change.  I
can't see how electrical interference could be a
problem.  Then again, I'm not an electrician.  Am I
missing something?  I recently put the heater back in,
but the controller had been acting funny before that. 
No other electrical equipment in the tank!  

The American Marine guy said that bubbles collecting
on the little bulb part of the pH probe can throw
things off a bit, but there was just as much pearling
when I put in in as now (if not more).  I'm assuming
that's where the bubbles come from.  

Even if that's the case, how can the controller and
the kit be so different?  I'm thinking of just taking
the thing out and saving it for the reef (I don't care
for kalk) if it's really any good.      

Stumped in Pittsburgh, Cavan    

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