||PINPOINT® pH Controller
II. General Specifications
III. Displays & Adjustments
IV. pH Calibration
V. Important Note on Probe Placement
VI. Adjusting the Controller Setpoints
VII. pH Monitor Theory
This device consists of a pH Monitor and electronics,
which control external devices, based on the pH reading. Accordingly,
there are two adjustments that must be made to the controller before
putting into service. The calibration of the electronics which read the
pH and the adjustments of the controller setpoints. After the controller
is in service, it will be necessary to re-confirm and perhaps
re-calibrate the pH monitor.
It is important that you understand these instructions and it is
critical that you follow the cautions in this manual. Most users will be
controlling the addition of CO2 into their system with this instrument and there can be disastrous results if CO2,
another acid or a base is added to the system in an uncontrolled
fashion. It is critical that one pay special attention to the placement
of the pH probe in the system. You must frequently check the condition
and calibration of the pH probe. We strongly require that you build
sanity into your system. Needle valves, and similar devices, should be
designed to throttle-down the flow of gases into the system at a
reasonable rate. If a base is being added, the maximum rate of addition
should be slow enough so that there are not disastrous consequences over
a short period of time. Control electronics are not human, they are not
intelligent and they can not "know" when something has happened to make
their input or output invalid. If the probe is not immersed in the
system, it will no longer be reading the correct pH; either acid or base
might be added in a completely uncontrolled fashion. If the solenoid
valve sticks open, the controller will not be able to shut it off. So
you must be very certain that the pH probe will not become uncovered and
your needle valve settings should be chosen so that if the control
solenoid valve sticks open, you will have some reasonable period of time
to notice that there is a problem. Installing a pH Controller on your
system does not mean that you no longer have to pay attention to it. You
must still monitor the system so that you can note when a problem
exists and correct it in a timely fashion.
II. GENERAL SPECIFICATIONS
pH Measurement Range 1.00 – 14.00
pH Setpoint Range 4.00 – 10.00
3 1/2 Digit LCD Display
Resolution 00.00 pH Unit
2 Independent 5 Amp 110 VAC Relay Outputs
III. Displays and Adjustments
pH Monitor Adjustment & Instrument Status
Controller Set Point Block
Controller Status LEDs
110 VAC Outlets (#1 & 2)
UPPER LEFT (pH Display)
The 3 1/2 digit LCD (Fig. A) at the top left of the
controller displays a numeric value corresponding either to the pH as
measured through the probe, or the high or low controller setpoints.
LOWER LEFT (pH monitor Adjustment & Instrument Status)
Below the display are two adjustment screws, which are
used to calibrate the electronics to properly read the pH, and two LED’s
which report the status of the instrument.
The adjustment screw marked "CALIB" (Fig. B) is used to zero the
pH monitoring electronics, and the "SLOPE" (Fig. C) is used to adjust
the slope. Detailed information on how to make these adjustments is
The red POWER LED (Fig. D) is illuminated when the power is
turned on to the controller. The pH LED (Fig. E) is illuminated when the
display is indicating the pH as measured through the probe with the
slide switch in the “read” position. The pH LED is off when the display
is indicating either the high or low controller setpoints.
CENTER (Controller Setpoint Block)
There are two potentiometers that are used to adjust the
controller setpoints. They control the RANGE (Fig. F) and CENTER VALUE
(Fig. G) of the controller, respectively. Detailed information regarding
their adjustment is given later in the ADJUSTING THE CONTROLLER
LOWER RIGHT (Display Mode)
The position of the SLIDE SWITCH (Fig. H) determines what
the LED display will show. At the center position, the display indicates
the pH that the probe is measuring, and the red pH LED (Fig. E) at the
lower left of the instrument will be illuminated. Sliding the switch up
or down will cause the display to show the high and low controller
UPPER RIGHT (Controller Status LEDs)
There are a total of 4 LEDs here. The upper row (Fig. I)
shows the status of the 110 VAC outlets, which you will find, on the
back of the controller beneath the LCD pH display. The lower LED lights
(Fig. J) are activated when the slide switch is in either the HIGH or
110 VAC OUTLETS
There are two outlets, which will be energized when the pH
is above (outlet #1) or below (outlet #2) the controller setpoints. A
common application for the controller will be to control the addition of
CO2 to the system. Since the addition of carbon dioxide lowers the pH, a NORMALLY CLOSED solenoid valve controlling the flow of CO2
would be plugged into the HIGH control outlet (Outlet #1). If a basic
substance is being dispensed into the system (i.e. a lime water reactor
for a reef aquarium) the device(s) controlling the flow would be
attached to the LOW control outlet # 2.
NORMALLY CLOSED means that the valve will be closed when NOT energized.
A pH electrode is supplied with the controller. A plastic
fluid-filled cap will protect the end of the electrode. The fluid inside
the cap is a mixture of #4.0 calibration fluid + 3M KCL. This is
commonly known as storage fluid. There is a suction cup attached to the
electrode, which may be used to secure it, or a user-devised scheme of
holding the electrode may be employed.
IV. CALIBRATING THE pH METER SUBSYSTEM
This is a two-point calibration instrument therefore TWO
different calibrations must always be used. A pH 7.00 fluid must be used
to set the CALIB and a pH 10.00 or 4.00 fluid is used to set the slope.
you begin the calibration, you should disconnect the pumps or valves
that you are controlling, because the pH electrode will be put into
solutions with a pH that is probably far outside the controller limits
you have established.
Before you begin, make sure that you have the pH calibration
fluids, and some room temperature tap water to rinse the electrode
between calibration solutions. You must have a #7.00 calibration
solution, and another solution with either be higher or lower pH
(typically 4 or 10). If you are doing this for the first time, read
through these instructions once to determine what is required before you
- Set the display mode switch (far right) to the central position (read). The pH LED (lower left) should be illuminated.
the plastic cap protecting the end of the electrode if you are doing
this for the first time. If the electrode has already been in service
you should note the condition of the electrode and clean it if required.
the electrode with room temperature tap water taking cares to remove
any accumulated salt. Rinsing the electrode prevents you from carrying
over contaminating substances into the calibration solutions. Gently
shake the electrode to remove any clinging drops of water.
the tip (bottom 1 inch) of the electrode into the pH 7 calibration
fluid. It is important to use the pH 7 solution first. Be sure that the
tip of the probe is fully immersed in the calibration fluid for a stable
and reliable result.
the glass bulb immersed, gently swirl the ends if the electrode in the
calibration fluid until the pH reading stabilizes. If the electrode is
in good condition, the reading should stabilize in a few seconds. If the
electrode does not easily stabilize; this may be a sign that the
electrode is in need of cleaning or should soon be replaced.
- Adjust the CALIB screw to bring the displayed pH to about 7.00
the electrode from the pH 7.0 calibration solution and rinse it with
room temperature tap water. Gently shake the electrode to remove
clinging drops of water.
the end of the electrode into either the low or high calibration fluid.
Usually pH 4 or pH 10 is the most common. Swirl the end of the
electrode in the fluid until you obtain a stable reading, then adjust
the SLOPE screw until the display shows the value of your calibration
fluid (typically 4.00 or 10.00).
- Again, rinse the electrode with room temperature tap water and shake of any clinging drops.
the electrode in the pH 7 calibration solution and now repeat steps
6–7–8 until the display shows 7.00 in the pH 7 fluid and 4.00 or 10.00
in the other calibration fluid that you have selected.
the electrode and return it to service in your system. Remember that
the sensitive glass bulb of the electrode must not be allowed to dry
out. Use the clear plastic cap filled with storage fluid or pH 4
calibration fluid when not in use.
The pH calibration process is now complete.
V. PROPER PLACEMENT OF THE pH ELECTRODE
When the controller is operational, it is critical that
the tip (bottom 1-inch) of the electrode be immersed in the system at
all times. If the water level falls below the sensing tip of the
electrode, the pH probe will not read properly. If the erroneously
measured pH is higher than the controller setpoint, devices connected to
that outlet will remain permanently ON, irrespective of the actual pH.
Take some time to determine how much the fluid level around the
probe will fluctuate. Adjust the position of the probe accordingly.
Consider the final placement of the probe and attach it securely
so that it remains in position. Be sure to check the probe position
occasionally. Complacency usually sets in when you feel that "Everything
is running fine."
VI. ADJUSTING THE CONTROLLER SETPOINTS
The PINPOINT® pH Controller is
capable of controlling pH within the range of pH 4 through pH 10. After
the selection of the pH setpoint you will find that the controller can
create a span around this setpoint, both above and below, from about +/-
0.1 pH unit to +/- 1.0 pH unit.
Two adjustment screws on the front panel determine the
controller pH setpoints. The right adjustment screw determines the
"center value" or the point halfway between the high and low setpoints.
The left adjustment screw controls the range both above and below the
selected pH setpoint.
As an illustration of how the two adjustments are related, consider the following:
When the measured pH moves from the center of the acceptable pH
range to above the high setpoint, the device attached to the HI outlet
is activated and will remain ON until the pH is brought to the center
Adjusting the Controller Setpoints
Determine the "Center Value" that you wish to establish
and the range around this center value you feel is acceptable (between
+/- 0.1 and 1.0 pH units). Remember, if you are only adding CO2, you
will have pH control in only one direction.
For example, if the acceptable range is a total of .4 pH
units from a LOW of 6.8 to a HIGH of 7.2 this means that the center
value is 7.0 since it is equidistant from 7.2 and 6.8 When the pH rises
to 7.2 the CO2 will be activated (Outlet #1) until the pH reaches 7.0
(Center Value) at which time it will be turned off.
If you would like to use a different center value, 8.0 for
example, then adjust the center value screw until the HIGH setpoint is
8.2 This will make the LOW setpoint 7.8 If you would like the range to
be a total of .2 pH units then adjust the range screw accordingly. If
you would like to have a larger range of .8 pH units then adjust the
range screw accordingly.
Remember to slide the switch between the HIGH and LOW positions
to determine the center value as well as the range that you have
selected. Keep in mind that the Center Value is not displayed and must
be calculated as the average of the HIGH and the LOW setting.
VII. pH Monitor Theory
To make the above adjustment of the pH meter portion of
the controller more comprehensible, this is a brief discussion of how pH
There is a special glass bulb that is in contact with the
solution. There are also special solutions inside the body of the
electrode, and a liquid junction that allows minute amounts of ions to
exchange between the electrode body and the solution. This junction
completes the electrical circuit. The pH Electrode acts like an
extremely weak battery, whose voltage is dependent upon the amount of H+
ions present in solution. Because the electrical properties of this
special glass are dependent on the H+ ion concentration of the solution
in contact with the glass bulb. Because this current is very small, the
signal must be handled very carefully, and the electronics in this
monitor have been specially designed to handle very weak voltage,
measure it accurately, translate it from a voltage to pH units, display
that quantity and pass it to the controller subsystem.
The voltage output from this very weak battery happens to be 0 mV
at pH 7. This is why a pH 7 solution is always used to "zero" the
meter. The zero happens to be marked CALIB on the instrument case. A
second standard solution, with either a pH higher or lower than 7
(usually 4 or 10) is used to adjust the slope for the response of the
electronics. Since the pH scale is linear in nature you may be
interested to know that this instrument will adjust 59mV per pH unit
Copyright / Warranty
PINPOINT® pH Controller
by American Marine inc. is warranted to be free of defects in Material
and workmanship for a period of 2 years from date of sale. Positive
proof of purchase is required for warranty claim.
American Marine Inc. will not be liable for any costs of removal,
installation, transportation charges, or any other charges, which may
result in connection with a warranty claim.
American Marine Inc. will not be liable for any damage or wear to
products or livestock caused by abnormal operating conditions, water
damage, abuse, misuse, unauthorized alteration or repair or if the
product was not installed in accordance with the printed operating
Any defective product must be sent freight prepaid with
appropriate documentation supporting the warranty claim. Replacement or
repair will be at the discretion of American Marine Inc. Typical
turnaround time within 48 hours. Overnight delivery available.
54 Danbury Road Suite 172
Ridgefield, CT 06877 USA
FAX/Phone 914 763 5367
PINPOINT pH Controller
***This example is for a CO2 dosing system. When CO2 is added to water; it will lower the pH of the water.
You must first select an acceptable range of pH like 6.6 to 6.4
At any pH value over 6.6 Outlet #1 will be energized and the CO2 will bubble into the water until the pH reaches the level of 6.4 At the 6.4 level the CO2 will shut off and stay off until the pH rises above the 6.6 level.
To achieve these setpoints, the selector switch should read 6.60
when placed in the HI position and 6.20 when put in the LO position. The
Center Value is the number that is exactly between the HI and the LO.
The Center Value in this example is 6.40 This Center Value must be
calculated; it is not displayed.
To arrange these settings (HI=6.60, LO=6.20, Center Value=6.40)
into the controller you must do the following 2 part adjustments.
- Put the selector switch to the HI position and
note the number. Then put the switch to the LO position and note the
number. By adjusting the RANGE screw in the center of the controller you
must create a difference of 0.40 between the HI and the LO. It is NOT
important at all which numbers are used, it is important that there the
difference of 0.40 between HI to LO. The numbers may be HI-6.40 and
LO-6.00 or perhaps HI-8.98 and LO-8.58. The only thing is that the
difference from HI to LO is 0.40 pH units.
- With the selector switch in the HI position, adjust the Center Value screw until it reads 6.60
That is all!
What you have done is to put the HI setting to 6.60 and the LO setting is 6.20 therefore the Center value is 6.40
PINPOINT pH Controller
Has control ability in both directions
In our example the setpoints are as follows:
The controller is set up to control CO2. There is a solenoid attached to Outlet #1 in the back of the controller.
When the pH of the water is above 6.60 the Outlet #1 will energize the solenoid and CO2
will bubble into the water until the pH of the water reaches the Center
Value of 6.40. When the pH value reaches the Center Value of 6.40 the
CO2 will shut off.
After the CO2 is shut down if the
water still has a falling pH then the LO setting is important. If the pH
of the water is below the LO setting of 6.20 then outlet #2 will
energize. Outlet #2 should have a regular air pump connected to it and
the air should disperse in the water by an airstone. The air will drive
off the extra CO2 and return the water to the Center value pH of 6.40 at that time the air pump will shut off.
***The American Marine line of pH and ORP Controllers are unique
because they can give control at both directions around the center
value. The user can determine the range of acceptable pH around the
Calcium Reactor Theory and Setup