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Re: CO2 regulators
> Date: Sat, 9 Sep 2000 03:09:42 -0400
> From: Ellen & William Beckerman <e_mail at bellsouth_net>
> Anyone else out there with anything info good, bad or indifferent on
> CO2/pH controllers???
I have an older '98 Pet Warehouse catalog at work and it lists a couple of pH
controllers. One in particular appears to be marketed by American Marine and is
a "Pinpoint pH Controller". This unit looks *exactly* like the original pH
controller sold by Sandpoint. IMHO, this unit is very poor, unless the design
has been updated.
The biggest problem we saw with it was it would oscillate between on and off at
it's tightest setting. You can adjust both the set point (i.e., "7.0") and the
hysteresis (i.e., "+/- 0.2"). If you chose the tightest hysteresis, you would
often wake up to a buzzing noise as it hunted for the right state. My analysis
was poor power supply bypassing. When the controller actuated the CO2 solenoid,
the circuit supply voltage jumped, altering the pH value read. The unit would
then see the pH being above the set point and would turn the solenoid off. Then
it would see the pH being below the set point. Repeat until whacked upside the
head by owner.
Another shortcoming was the ergonomics. It had knobs for doing the calibration.
It had recessed slotted screws for the set point and hysteresis. It was very
easy to bump the knobs and knock it out of calibration. Why on Earth did they
use knobs for cal?
George Booth in Ft. Collins, Colorado (booth at frii_com)