Myron L 729II - Manual (Page 50)

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C. SETUP PROCEDURES
These Setup procedures cover (1) converting the alarm circuit to
trigger on a decreasing or increasing reading, (2) checking out
your new Monitor/controller, (3) setting the alarm circuit set
point(s), and (4) adjusting the hysteresis.
The following require that the front panel be removed. While doing
so be careful not to strain the cable(s).
NOTE: A small screwdriver or tweaker will be required for several
of the following operations.
1. SET POINT CONVERSION (SPC) /
REVERSING SET POINT
The alarm/control circuit(s) on all 720 Series II pH/ORP
Monitor/controllers are configured to trigger the alarm relay as the
reading increases.
If the user’s application requires it, the alarm circuit may be easily
reconfigured to trigger the alarm relay as the reading decreases.
Refer to figure V.A.1. for the locations of the jumpers referred to
in this section.
NOTE: These instructions describe the general procedures for
converting the Monitor/controller without reference to jumper
numbers or orientation.
1. Ensure power is OFF.
2. Locate the jumper block for the alarm to be configured.
3. Make a note of the current orientation of the jumpers.
4. Remove both jumpers. This is easily done by hand. Take
care not to crush the jumpers if using pliers.
5. Rotate the jumpers 1/4 turn and reinstall them on their
posts as shown in figure IV.C.1.
2. CHECK-OUT PROCEDURES
The following check-out procedures are used to verify that the
720 Series II Monitor/controller is operating properly. It is
assumed that the Monitor/controller is powered ON, that it is
connected to an appropriate Sensor, and that the Sensor is
immersed in water within the range that the Monitor/controller will
be required to read. Refer to figure V.A.1. for the locations of the
components referred to in this section.
a. Make a note of the reading on the display.
b. Being careful not to strain the connecting cable(s),
unfasten and remove the front panel.
c. While pressing the ZERO Test Switch (ZERO), verify that
the front panel display is indicating 7pH or 0 mV reading.
If not, see Calibration, section V.C.
d. Press and hold the “SET POINT” switch on the front
panel. Using the tweaker or a small screwdriver, adjust
the Set Point trimmer adjustment screw on the circuit
board to sweep the display left and right 1pH unit or 60mV
on both sides of water reading. Listen for the alarm relay
to click ‘ON and OFF’ as the alarm set point moves past
the water reading.
e. Adjust the alarm to the desired set point value. Release
the “SET POINT” switch.
NOTE: For Models with SC/SCO module, repeat STEPS 4 & 5 to
check out Set Point #2.
3. SET POINT ADJUSTMENT
The set point setting is based upon the user’s particular water
purity specifications or requirements.
NOTE: The optional second relay/alarm is “stacked” on the first
relay/alarm, therefore, when setting the optional second
relay/alarm Set Point, the #1 Set Point must be ‘set’ first.
a. Being careful not to strain the cable, unfasten and
remove the Monitor’s front panel.
b. While depressing the “SET POINT” switch, turn
the Set Point #1 adjustment screw (See figure V.A.1)
until the desired set point value is indicated on the
display.
c. If Hysteresis adjustment is required see below. If not,
reinstall the front panel and tightly secure both retaining
screws.
4. HYSTERESIS (DEAD BAND) ADJUSTMENT
The hysteresis or dead band is approximately ±3% of the set point
at full scale as it leaves the factory. Under normal (most)
conditions it will not be necessary to adjust.
However, if you desire to make an adjustment please keep the
following in mind.
The adjustment is very simple and is based on set point location.
If the set point* is in the upper 75-100% of the scale, the
hysteresis control pot should be turned fully to the right.
If the set point is in the lower portion of the scale, i.e. 5-25 % of
scale, the control pot may be turned fully to the left.
If you are operating in the center, 25-75% of scale, the control
pot may be adjusted in the center.
Or the hysteresis or dead band may be adjusted to tighten the
control of a particular process.
CAUTION: adjusting the hysteresis too tight may cause the
alarm to fluctuate (on-off) due to flow, chemical mixing or bubbles
causing the relay to chatter. This condition is to be avoided, it
could damage your valves, pumps, etc. and will eventually
damage the relay.
* Applies to both set points if so installed.
The following is assuming the front panel is already removed and
the set points have been set, if not see above,
1. Locate the hysteresis control adjustment located next to
the Set Point #1 (SP1) adjustment - it is a single turn pot.
See figure V.A.1.
2. Adjust as described above or as desired.
3. Reassemble per below.
!
CAUTION - READ FOLLOWING CAREFULLY
JUMPER CONVERSION
Figure C.1
INCREASING DECREASING