Myron L 767 - Manual (Page 12)

3.3.1 DECREASING SET POINT CONVERSION
The alarm circuit(s) on all 750/760 Series Conductivity Monitors
are configured to trigger the alarm relay as the conductivity (or
ppm) reading increases. If the user’s application requires it, the
alarm circuit may be easily reconfigured to trigger the alarm
relay as the conductivity (or ppm) reading decreases. Refer to
Fig. 4-1 for the locations of the jumpers referred to in this
section.
NOTE:
These instructions describe the general procedures for
converting the Monitor without reference to jumper numbers or
orientation. Refer to Fig. 3-2 or 3-3 for the specifics on your
Monitor.
STEP 1 Turn OFF or disconnect the Monitor’s main AC power.
STEP 2 Locate the jumper block for the alarm to be configured.
STEP 3 Make a note of the current orientation of the jumpers.
STEP 4 Remove both jumpers. This is easily done by hand.
Take care not to crush the jumpers if using pliers.
STEP 5 Rotate the jumpers and reinstall them on their
posts.
Operating Procedures
3.4.1 MODEL 755 (Only)
STEP 1 Turn the front panel adjustment knob to its full scale
setting. The green “BELOW SET POINT” light should
be ON indicating that the water being monitored is
BELOW the controller’s monitoring set point.
STEP 2 Turn the front panel adjustment knob to its zero scale
setting. The red “ABOVE SET POINT” light should be
ON indicating that the water being monitored is ABOVE
the controller’s monitoring set point.
STEP 3 Turn the adjustment knob back and forth and note the
reading where the ABOVE and BELOW LED indicator
lights switch. Also note an audible click as the relay
picks up and drops out. This reading corresponds to
the actual water purity.
STEP 4 Reset the Set Point trimmer adjustment knob to the
desired set point.
3.4.2 MODELS 756, 757, 758, & 767
NOTE:
A small screwdriver will be required.
STEP 1 Make a note of the reading on the Monitor’s display.
STEP 2 Being careful not to strain the connecting cable(s),
unfasten and remove the Monitor’s front panel.
STEP 3 (For the Model 767 only!) Place the “RANGE” select
switch to its “X1” setting.
STEP 4 While holding the Calibration Test switch (SW1) to its
TEST position, verify that the front panel meter is
indicating a full scale reading.
STEP 5 Press and hold the “SET POINT CHECK” switch on the
front panel. Using the small screwdriver, adjust the Set
Point trimmer adjustment screw on the circuit board to
sweep the display from zero to full scale. (A digital
display may be blank at the full scale end. This is
normal.) Listen for the alarm relay to click on and off as
the alarm set point moves past the water reading.
STEP 6 Adjust the alarm to the desired set point. Release the
“SET POINT CHECK” switch.
NOTE:
For Model 767-DP, repeat STEPS 5 & 6 to check out Alarm B.
3.3.2 SET POINT ADJUSTMENT
NOTE:
Because the Model 755 is equipped with a standard front panel
Set Point trimmer adjustment knob, it does not have an internal
set point adjustment setting. Refer to Section 3.4.1 for
procedures to adjust the 755’s set point.
STEP 1 Being careful not to strain the cable, unfasten and
remove the Monitor’s front panel.
STEP 2 While depressing the “SET POINT CHECK” switch,
turn the Monitor’s Set Point trimmer adjustment screw
(See Fig. 4-1) until the desired set point value is
indicated on the meter display.
NOTE:
The Monitor’s set point setting is based upon the user’s
particular water purity specifications.
STEP 3 After successfully completing STEP 2, remount the
front panel and tightly secure both retaining screws.
3 .4 CHECK-OUT PROCEDURES
The following check-out procedures are used to verify that a
750/760 Series Conductivity Monitor is operating properly. It is
assumed that the Monitor is powered ON, that it is connected to
a CS51 or CS52 Cell, and that the Cell is immersed in water
within the range that the Monitor will be required to read. Refer
to Fig. 4-1 for the locations of the components referred to in this
section.
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