Carbon Monoxide Alarm User Manual

Page 24
Chapter 5 PhD2 Advanced
Functions
5.1 PhD
2
Advanced features overview
The PhD
2
microprocessor circuitry makes a number of
advanced features and capabilities possible. Although
this chapter has been designed primarily to be of benefit
to "experts" there are several sections that may be of
interest to other PhD
2
users.
The four push buttons located under the keypad cover on
the top of the detector are used to program advanced
PhD
2
functions. The technique for using these buttons
requires several buttons to be pressed and held at the
same time.
CAUTION: Do not use this technique with any other
combination of buttons than those listed below.
Doing so may result in loss of information stored in
memory.
The major advanced functions and set-up routines
available through this method are Diagnostics, and
Sensor Configuration. The sensor configuration routine
in particular controls a number of potentially useful
alternative set-up configurations.
5.2 Diagnostics Test
The "Diagnostics Test" mode is used to identify
problems with various PhD
2
components. It is most
useful in helping identify whether a sensor needs to be
replaced.
Accuracy of the PhD
2
must be checked with known
concentration calibration gas before each day's use.
Unstable or erratic readings, or inability to calibrate may
indicate a sensor is approaching the end of life or has
been contaminated.
Sensors that cannot be calibrated
should be replaced immediately.
5.2.1 Entering the Diagnostics Test mode
The Diagnostics Test routine is entered by using the
MODE button to turn the detector on while simultaneously
holding the "+" and
"-" buttons down. The message "Diagnostic Test" will
briefly appear on the screen. The screen will also
indicate the version of the PhD
2
microprocessor software
currently installed.
This screen will be followed by another which briefly
shows the release date of the software version currently
installed in the PhD
2
, and the instrument identification
number.
The next screen shows the raw output of the combustible
gas (LEL) and oxygen sensors. Please note that LEL
values (250 counts in the example screen below) are
listed to the left, oxygen values (755 counts) to the right
hand side of the screen.
By pressing the MODE button, you can advance to the
next screen which shows the raw output for the toxic
sensors. The values for the sensor installed in Toxic
sensor channel #1 are listed to the left, Toxic sensor
channel #2 to the right.
5.2.2 Diagnostic counts
Diagnostic counts represent the raw electrical output of
the sensors installed in the PhD
2
. A "healthy" sensor will
generally have an output within an expected optimum
performance range.
Note: Optimal sensor performance ranges are
approximate! PhD
2
diagnostic counts should only be
used as a gross indication of the health of the
sensor.
Significant differences in diagnostic counts may be seen
from one sensor to another. Diagnostic counts may also
be affected by the age of the sensor and the battery
voltage.
Make sure that the battery is fully charged before
entering the diagnostic mode with the intent of
checking sensor performance!
Optimal ranges vary for different PhD
2
microprocessor
versions.
Make sure you have the correct optimal values for
the instrument being checked!
The following ranges only apply to PhD
2
detectors with
version 4.7 microprocessor software installed. Please
contact the factory for the correct ranges for other
software versions.
The most appropriate use of the diagnostic counts is to
verify an existing suspicion that a sensor requires
replacement. In the event that a sensor is incapable of
calibration, diagnostic counts may help to determine that
it is the sensor that is truly at fault, and a replacement is
required. Using the diagnostic counts may also help to
determine whether it is time to change an "old" out of
warranty sensor that is still functional, but that may
approaching the end of its life.