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i) If you wish to change the measuring unit to ppm, press CALL a number of times
to return to “%sat/ppm” and change ppm with the down button.
j) Press RUN to return to on line measurement.
NOTE: If a major change is necessary to make the display read 100% the display
will flash when you press ENTER. This is to warn that you may have made
a mistake such as using “stale” water. If you are confident your procedure
was correct, press ENTER a second time. Otherwise, repeat the calibration
procedure by pressing CALL a sufficient number of times to go through the
menu and return to CALIBRATION.
5.4 Analog Output Range Expand
5.4.1 The 4-20 mA isolated analog output may be spread over any section of the scale as
long as that section is at least 10% of full scale. The best way to describe this
setup is by example. Suppose you wish the 4-20mA output to span 5 ppm to 10
ppm. Proceed as follows:
a) Press CALL as many times as required until OUTPUT HIGH is indicated. Now
use the arrows to make the meter read 10 ppm. Press ENTER. The display
will flash until ENTER is pressed again to confirm entry.
b) Press CALL once to indicate OUTPUT LOW. Now use the arrow buttons to
make the meter read 5 ppm. Press ENTER twice as above.
c) The analog output will now be at 4 mA when the D.O. of the solution is 5 ppm
and will increase to 20 mA when the D.O. of the solution is 10 ppm.
d) Press RUN to place the instrument on line or press CALL for another menu
selection.
e) To invert the output (i.e. decreasing output for increasing process value) simply
adjust for 4 mA on OUTPUT HIGH and for 20 mA on OUTPUT LOW.
NOTE: A range expand of less than 10% of full scale is an invalid entry which will
be indicated by the LED flashing when you return to RUN. To correct,
return to the menu and correct the output settings.
5.5 Test
5.5.1 To test your setup press CALL the number of times required to indicate TEST. Now
by using the arrow buttons you can “sweep” through the digital display.
5.5.2 With the instrument in TEST you can check the analog output at any desired
reading with a meter connected to the appropriate output terminals.
5.5.3 Another use of this feature is to check the stability of the system. When in TEST,
use the arrow buttons to select any value, say 10 ppm. Now return online by
pressing RUN. Return to the meter some hours or days later. Press CALL to
indicate TEST. If the instrument is still in calibration and if no one has interfered the
meter should read 10 ppm.