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MODEL 54e pH/ORP SECTION 8.0
TROUBLESHOOTING
8.1 DISPLAYING DIAGNOSTIC VARIABLES
This section explains how these helpful diagnostics can be viewed:
1. Electrode input in mV: Used to check if the signal produced by the
sensor is within acceptable limits (see Figure 8-1 for typical sensor
mV response at 25°C).
2. Glass impedance in M
ΩΩ
: Used to check integrity of glass electrode.
Broken glass membranes will have low impedance.
3. Reference impedance in k
ΩΩ
: Used to indicate how coated the ref-
erence electrode has become. Coated or plugged sensors will have
high values of reference impedance.
4. Zero offset in mV: Indicates the deviation from the typical sensor
response (Figure 8-1) as of the last buffer calibration. The controller
compares the value at 7 pH with the ideal value of zero mV at 7 pH.
5. Slope in mV/pH: Indicates the sensitivity of the glass electrode. This
number tends to drop as a sensor ages. Values below 47 are con-
sidered too low for calibration.
6. Software version
Use the following procedure :
1. From the main display, press any key.
2. With the down arrow key, move the cursor down to "Diagnostic
Variables" and then press Enter (F4).
3. Diagnostic variables are displayed three at a time. More variables are
viewable until the cursor (showing highlighted text) is brought down
to the bottom line.
Use the down arrow key to view the items on the lower screen.
The up arrow key can be used to return to a previously viewed item .
Press the Exit (F1) key to return to the main menu above.
NOTE
Many diagnostic variables can be read directly on the main dis-
play in the lower left or lower right positions. For details, see
Section 5.5.
Calibrate
Diagnostic Variables
Program
Exit
Zero offset: 0 mV
pH slope: 59.02 mV/pH
Version: pH1.01
Exit
Input: 120 mV
Glass imped: 300 MΩ
Ref imped: 8 kΩ
Exit
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