9
8
• Switch the meter on and press the RANGE
key to enter the mV mode.
• Submerge the ORP electrode tip (4 cm /
1½") into the sample. Allow a few minutes
for the reading to stabilize.
• The meter displays the mV reading on the primary LCD.
• If reading is out of range, "---" will appear on the LCD.
TAKING TEMPERATURE MEASUREMENTS
Connect the
HI 7669/2W
temperature probe
to the proper socket on the rear panel and
turn the instrument on. Dip the temperature
probe
in the sample and allow the reading to
stabilize.
HOLD FUNCTION
Press and hold the MEM key. The last reading will be frozen on the
display until MEM is released. During this operation, the MEM
indicator is also shown on the LCD.
Press MR to recall the previously memorized
reading. The value will be displayed with the
MEM indicator on the LCD.
4 cm
(1½")
OUTPUT RECORDER FUNCTION
Connect the recorder to the analog output socket and turn the
instrument ON. The value on the analog output will be related with
the pH or mV value displayed on the LCD as follows:
pH:
0
7
14
mV:
-2000
0
2000
analog output:
0 V
2.5 V
5 V
RESET
The RESET button (#14 on page 4) should only be used when the
instrument displays erroneous messages due to strong electrical inter-
ference or when the power supply was disconnected before switching
the meter off.
After pressing RESET, always recelibrate the unit before proceeding.
pH CALIBRATION
Frequent calibration is recommended. Moreover, the instrument should
be re-calibrated for pH:
a) whenever the pH electrode is replaced
b) at least once a week
c) after testing aggressive chemicals
d) if higher accuracy is required
e) after the RESET button has been pressed
PREPARATION
Pour small quantities of the buffer solutions into clean beakers. If
possible use plastic beakers to minimize any EMC interferences.
For accurate calibration and to minimize cross contamination use two
beakers for each buffer solution. One for rinsing the electrode and the
second for calibration.
If you are measuring in the acid range, use pH 4.01 as second
buffer; if you are measuring in the alkaline range, use pH 10.01 or
pH 9.18 as second buffer.
PROCEDURE
Five memorized buffer values are available for calibration: pH 4.01,
6.86, 7.01, 9.18 and 10.01.
Calibration can be performed at 1 or 2 points. For best accuracy, a 2
point calibration is recommended.
