Hanna Instruments HI 8614N - Manual (Page 6)

10 11
• Adjust the slope trimmer until the ammeter reads 8.58 mA for
HI 8614 and HI 8614L or the display shows "4.01" at 25°C. For
other buffer temperatures, refer to page 12 for the appropriate
mA / pH reading.
If you are using pH 10.01 buffer
solution adjust the slope trimmer
until the ammeter read 15.43 mA at
25°C (77°F) or the value indicated at
page 12.
FOR HI 8614L ONLY
The Display Module is factory calibrated, so that the LCD display
results are referred to the 4-20 mA loop current (e.g. LCD displays
0.00 pH when the loop current is 4.00 mA and displays 14.00 pH
when the current is 20.00 mA).
Under normal application, adjustment on this module may not be
necessary.
If routine check is required, the following procedures shall be performed.
• Follow the procedure at page 10 to perform calibration on the
transmitter module (using a ammeter).
• Simulate a 4.00 mA loop current for the transmitter (i.e. 0.00 pH
as Electrode input) and check for display reading.
• Simulate a 20.00 mA loop current for the transmitter (i.e.
14.00 pH as Electrode input) and check for display reading.
Note: When HI 8614 or HI 8614L instruments are used in
conjunction with the new Hanna indicator HI 8510 or
controllers HI 8710 and HI 8711, the calibration can also
be performed on the indicator/controller. In this case slight
calibration adjustment can be made on the indicator/
controller even if the whole system calibration is advised,
always starting from the transmitter.
PROCEDURE
• Disconnect the +ve supply cable from "+VE LOOP" terminal and
connect a 20mA f.s. ammeter between the +ve cable and "+VE
LOOP" terminal.
• Remove the protective cap from the electrode,
rinse it with some pH 7.01 solution or immerse it
in the pH 7 rinse solution, then immerse the pH
electrode and temperature probe into pH7.01
calibration buffer solution; shake briefly and wait
for the reading to stabilize.
Note: The tip of the electrode should be
submerged approximately 4 cm (1½")
into the solution. The temperature probe
should be located as close to the pH
electrode as possible.
• Adjust the offset trimmer until the ammeter reads 12 mA or the
display shows "7.01" if the temperature of the buffer is at 25°C.
For other buffer temperatures, refer
to page 12 for the appropriate
mA / pH reading.
• Rinse the electrode with tap water or distilled
water and a small amount of pH 4.01 or 10.01
buffer solution or immerse it in the pH 4 rinse
solution (2nd calibration point). Dip the electrode
and the temperature probe into pH 4.01 (or
10.01) calibration buffer solution, shake briefly
and wait for a few minutes for reading to stabilize.