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CHAPTER 5. ADVANCED
FUNCTIONS
5.1
ZoneGuard Advanced features
overview
The ZoneGuard microprocessor circuitry makes possible a
number of advanced features and capabilities. The four
pushbuttons located on the inside of the controller housing
door are used to program advanced ZoneGuard 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 unintended changes to the instrument
setup.
5.2
Re-setting the calibration gas
concentration
During auto calibration adjustment the ZoneGuard adjusts
the sensitivity of the sensor to match the concentration of the
gas used to calibrate the sensor. The value the instrument
uses to adjust the reading is the calibration gas
concentration stored in the instrument memory.
For instance, Biosystems normally supplies 50 ppm carbon
monoxide calibration gas for use in calibrating CO
ZoneGuard detectors. This is the default calibration gas
concentration stored in the instrument memory. When gas
is applied to the sensor during auto calibration, the
instrument automatically adjusts the calibration constants to
produce readings which match this 50 ppm concentration.
Sensor
Gas used
to calibrate
sensor
True cal
gas con-
centration
Value used by
ZoneGuard to
adjust readings
Oxygen
Zero Air
20.9%
20.9%
Combustible
gas
Propane
Equivalent
50% LEL
50% LEL
Carbon
monoxide
CO
50 ppm
50 ppm
Hydrogen
sulfide
H2S
25 ppm
25 ppm
Sulfur
dioxide
SO2
10 ppm
10 ppm
Chlorine
Cl2
5 ppm
5 ppm
Chlorine
dioxide
Cl2
5 ppm
1.7 ppm
Phosphine
PH3
5 ppm
5 ppm
Nitrogen
dioxide
NO2
5 ppm
5 ppm
Table 5.2. Default calibration gas concentrations used
during auto-calibration adjustment
It is necessary to re-set the calibration gas concentration
stored in instrument memory before making use of a
different calibration gas concentration.
Do not reset the calibration gas
concentration unless you are using a calibration gas
concentration which differs from that normally supplied
by Biosystems for use in calibrating your instrument.
Non-matching calibration gas and calibration gas value
settings will lead to inaccurate and potentially
dangerous readings.
Customers are strongly urged to use only Biosystems
calibration materials when calibrating their ZoneGuard
detector. Use of non-standard calibration gas and/or
calibration kit components can lead to dangerously
inaccurate readings and may void the standard
Biosystems warranty.
Use the following procedure to re-set the calibration gas
concentration:
1. Make sure gas readings are given in numbers. If the
display shows “OK”, then the ZoneGuard is currently
being operated in the “Text Only” mode. To change
over to Basic mode, simultaneously hold down the "+"
and"-" keys as discussed in section 2.9.3. 2.
Turn the
instrument off by pressing the Mode button until the
display blanks.
3. While holding down the “+” button, press the Mode
button to turn the ZoneGuard back on.
4. The ZoneGuard LCD will display alternating “CAL” and
“GAS” messages for 4 seconds. The display will then
alternate between the current concentration stored in
memory and the “GAS” message screens.
5. Use the “+” and “-” buttons to change the concentration.
6. Once the proper new concentration has been selected,
press and hold down the “Alarm” button for three
seconds. Do not release the “Alarm” button until the
LCD displays the message “DONE” to indicate that the
new value has been successfully entered.
7. Pressing the Mode button at any time cancels the
procedure. The LCD will show the message “NO
SAVE” to indicate that the calibration gas concentration
values have not been changed.
