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PART THREE - OPERATION
SECTION 5 - TEMPERATURE CALIBRATION
Model 692P
Rev. 9-898
-30-
4.3 Selecting Temperature
Display Units (
°°
C or
°°
F)
4.4 Understanding
Calibration
4.5 Selecting Default State
for Out-of-Range
Condition
2. Indirect Hookup with Model 714 Preamp (distances more
than 10 feet)
A. Locate the group of four switches on back of display
module assembly (Figure 3-2) and place
SWITCH 3
in
COMB
. (on/left) position.
B. Set
TEMP. COMP.
switch to
THERM
position.
Locate the group of four switches on back of display module
assembly (Figure 3-2) and place
SWITCH 4
in
°°
F
(on/left)
position for temperature values to be displayed in
°
F. Place
in opposite
°°
C
(off/right) position for
°
C readout.
Before initially calibrating the instrument, read Section 5.1
“Temperature Effects on pH Reading” and Section 6.1
“Summary of Methods”. Then calibrate the instrument using
the desired method.
When an out-of-range condition occurs due to a defective
pH sensor or shorted sensor cable, the instrument will re-
spond according to the default state selected with
SWITCH
2
(Figure 3-2). Refer to Section 1.2 - item 10 for details
about this switch and its settings.
SECTION 5 - TEMPERATURE CALIBRATION
5.1 Temperature Effects
on pH Reading
300 Ohm
Thermistor
Compensation
1000 Ohm RTD
Compensation
The instrument automatically compensates the pH reading
for changes in temperature and has temperature calibration
capabilities. For best accuracy, it is recommended to ini-
tially calibrate the instrument for temperature before
calibrating for pH measurement.
When using a GLI Differential Technique pH sensor or a pH
combination electrode with a 300 ohm thermistor, you can
disregard temperature calibration. (The 692 is factory-
calibrated for this temperature sensor.) If, however, you
require extremely accurate temperature measurement, per-
form a single or two-point temperature calibration (Section
5.2 or 5.3) before calibrating the 692 for pH measurement.
When using a pH combination electrode with a 1000 ohm
RTD, always perform a two-point temperature calibration
before calibrating for pH to obtain the most accurate pH
readings.