Setting Up Diagnostics - Emerson Rosemount FCL-01 Reference Manual

Reference Manual
00809-0100-3412
4.8

Setting up diagnostics

4.8.1 Purpose of diagnostic setup
Note
Diagnostic setup applies only to pH sensors. It appears only if you are using the
Rosemount FCL-02.
This section describes how to do the following:
1. Turn pH sensor diagnostics on and off.
2. Set pH sensor diagnostic limits.
4.8.2 Diagnostics definitions
Diagnostics
Reference offset
Glass and
reference
impedance
Glass impedance
temperature
correction
Glass fault high
4.8.3 Set up diagnostics
Complete the following steps to set up diagnostics on your Rosemount FCL-02 pH sensor.
Procedure
1. Press MENU.
2. Move the cursor to
3. Scroll to the bottom of the screen and continue scrolling until
Rosemount FCL 1056
pH sensor diagnostics are useful in troubleshooting calibration
problems and in predicting when a pH sensor should be replaced.
Diagnostics can also alert you that the sensor is no longer submerged in
the process liquid.
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.
During operation, the transmitter continuously measures the
impedance of the pH glass membrane. If the pH sensor has a solution
ground, the transmitter also continuously measures the impedance
of the reference junction. The Rosemount 3900VP pH sensor supplied
with the FCL-02 has a solution ground. Glass and reference impedance
measurements provide useful information about sensor health and
cleanliness.
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.
A typical glass electrode has an impedance of about 100 MΩ. As the
sensor ages, glass impedance increases. Extremely high impedance
(greater than about 1000 MΩ) 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.
The main Menu screen appears.
Program
is highlighted. Press ENTER.
and press ENTER.
Programming the transmitter
October 2023
Diagnostic Setup
53