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MODEL FCL-1056 SECTION 5.0
PROGRAMMING THE ANALYZER
5.8 SETTING UP DIAGNOSTICS
5.8.1 Purpose
NOTE
Diagnostic setup applies only to pH sensors. It appears only if you are using the FCL-02.
This section describes how to do the following:
1. Turn pH sensor diagnostics on and off.
2. Set pH sensor diagnostic limits.
5.8.2 Definitions
1. DIAGNOSTICS. pH sensor diagnostics are useful in troubleshooting calibration problems and in predicting
when a pH sensor should be replaced. Diagnostics can also alert the user that the sensor is no longer
submerged in the process liquid.
2. REFERENCE OFFSET. pH sensors are designed to have a potential of 0 mV in pH 7 buffer. The reference
offset is the actual potential (in mV) in pH 7 buffer. A new sensor typically has a reference offset of a few mV.
Old sensors can have offsets of 60 mV or more.
3. GLASS AND REFERENCE IMPEDANCE. During operation, the analyzer continuously measures the imped-
ance of the pH glass membrane. If the pH sensor has a solution ground, the analyzer will also continuously
measure the impedance of the reference junction. The Model 3900VP pH sensor supplied with the FCL-02 has
a solution ground. The Model 399VP sensor, supplied with earlier versions of the FCL-02, did not have a solu-
tion ground. If you are using a 399VP sensor, reference impedance diagnostics will not be available. Glass
and reference impedance measurements provide useful information about sensor health and cleanliness.
4. GLASS IMPEDANCE TEMPERATURE CORRECTION. The impedance of a glass electrode is a strong
function of temperature. As temperature decreases, the impedance increases. For glass impedance to be a
useful indicator of sensor condition, the impedance must be corrected to a reference temperature.
5. GLASS FAULT HIGH. A typical glass electrode has an impedance of about 100 MΩ. As the sensor ages,
glass impedance increases. Extremely high impedance (greater than about 1000MΩ) implies the sensor
is nearing the end of its life. High impedance may also mean that the sensor is not submerged in the process
liquid.
3. The screen shows the existing security codes. To make a change, move
the cursor to the desired line and press ENTER. A screen will appear in
which the present setting can be edited. Press ENTER to store the
change. The security code takes effect two minutes after pressing
ENTER.
4. To return to the main display, press MENU then EXIT.
Security
Calibration/Hold 000
All 000
Calibration/Hold
5.7.2 Procedure – Configuring Security Settings
1. Press MENU. The main menu screen appears. Move the cursor to
Program and press ENTER.
2. Scroll to the bottom of the screen and continue scrolling unit Security is
highlighted. Press ENTER.
Program
Alarms
Measurement
Temperature
Security
Security