3-3
MODEL 2700 SECTION 3.0
CALIBRATION
glass containers. This solution (ferric-ferrous ammonium
sulfate) will produce a nominal ORP of 476 ±20 mV at
25°C. Some tolerance in mV values is to be expected
due to the rather large liquid reference junction poten-
tials which can arise when measuring this strongly
acidic and concentrated solution. However, if the mea-
suring electrodes are kept clean and in good operating
condition, consistently repeatable calibrations can be
carried out using this standard solution.
NOTES
The analyzer does not use the new
calibration values unless the START
CALIBRATION prompt has been
highlighted and ENTER ( ↵ ) has been
pressed.
The Conductivity, pH, or Temperature
readings are the last sensor values read
before entering the Calibrate menu
mode.
If the value displayed is ok, the next
field to be changed can be accessed
by either pressing ENTER ( ↵ ) or NEXT
(F3).
If a new pH, ORP, or Conductivity value
cannot be entered (pressing the
scrolling keypads has no effect), verify
that the new conductivity value does
not exceed the new value by more than
± 5%.
If a new Temperature value cannot be
entered (pressing the scrolling keypads
has no effect), verify that the new
temperature value does not exceed the
raw value by more than ± 2 Deg C.
If the pH reading is unstable, run a wire
from pH preamp (P/N 23054-03)
terminal block 2, terminal 2 into the
buffer cup. This wire acts as a solution
ground for those sensors without one.
ORP of Saturated Quinhydrone Solutions (in Millivolts)
pH 4 pH 7
Temp. °C 20 25 30 20 25 30
Millivolt Potential 268 264 260 94 87 80
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