biosystems PhD Lite User Manual

39
4.4 Automatic calibration
Biosystems one-button auto-calibration procedure may
be used to calibrate the PhD Lite at any time during
normal operation in all modes except Text-Only Mode.
Auto-calibration is a two-step procedure. In the first
step the PhD Lite is taken to an area where the
atmosphere is known to be fresh and a fresh air
adjustment is made as detailed below.
The second step is the sensor response or "span"
calibration adjustment. In this step the accuracy of the
PhD Lite sensors is established by exposing them to
known concentration calibration gas(es). The sensitivity
or “span” is automatically adjusted by the instrument.
Note: If the Passcode and Span Lock functions are
enabled, the PhD Lite will prompt the user for the
passcode prior to entering the span calibration
subroutine. See section 3.4.4.3 for further details.
4.4.1 Automatic fresh air/zero calibration
sequence
The automatic fresh air calibration procedure may only
be performed while the instrument is being operated in
Technician, Basic/Peak or Basic operating modes.
1. Turn the instrument on and make sure gas readings
are given in numbers. (This is an indication that the
PhD Lite is currently in Basic, Basic/Peak or
Technician Mode).
If sensor readings are displayed in the form of “OK”
text messages, the instrument is currently in Text-
Only mode. It will be necessary to change the
operating mode to Basic, Basic/Peak or Technician
mode as explained in section 2.3.5 before
proceeding with the calibration.
2. Wait at least three minutes after turning the
instrument on to allow sensor readings to stabilize
fully before initiating any calibration procedures. If
a sensor has just been replaced, follow the sensor
stabilization schedule in section 6.1.1.
3. Make sure the instrument is located in an area
where the air is known to be fresh.
4. Press the MODE button three times within two
seconds. This will "wake up" the instrument from
normal operation, and initiate the auto-calibration
sequence. A screen will briefly display the
message “One Button Auto-Calibration”.
One Button Auto
Calibration
The instrument will then proceed to the following screen
and begin a 5-second countdown.
Zero Calibration
Mode = Adjust 5
5. To initiate the fresh air/zero calibration, press the
MODE button before the unit finishes the
countdown.
Zero Calibration
Please Wait
Zero Calibration
Completed
Upon successful completion of the fresh air/zero
calibration, the instrument will automatically proceed to
the automatic span calibration sequence.
4.4.1.1 Reading “Too High” or “Too Low” for zero
adjust
To reduce the chances of the PhD Lite being
inadvertently fresh air/zero calibrated in contaminated
air, only small adjustments are allowed in the automatic
fresh air/zero calibration sequence. If the necessary
adjustments are too large, the display will indicate the
sensor (or sensors) affected, and a message screen will
indicate that the reading is “Too Low” or “Too High” for
zero adjustment. In this case the instrument must be
fresh air calibrated using the manual calibration
procedures as discussed in section 4.5.1 of this manual.
Oxygen Too Low
for Zero Cal
Once the instrument has been successfully fresh air
calibrated using the manual fresh air calibration
procedure, subsequent calibration adjustments may be
made using the MODE button and automatic calibration
logic discussed in this section.
4.4.2 Automatic span calibration sequence
Following the completion of the automatic fresh air
calibration, the PhD Lite will display the countdown for
the automatic span calibration:
Note: If the Passcode and Span Lock functions are
enabled, the PhD Lite will prompt the user for the
passcode prior to entering the span calibration
subroutine. See section 3.4.4.3 for further details.
Span Calibration
Mode = Adjust 5
If span calibration is not required, allow the unit to
complete the 5-second countdown without pressing any
buttons.
Press MODE before the before the end of the 5-second
countdown to initiate the automatic span calibration
sequence. The PhD Lite will then display:
Apply Gas
MODE = Cancel
Attach the cylinder of calibration gas to the PhD Lite
through the regulator, tubing and calibration adapter as
shown below in figure 4.4.2. Continue to flow gas
throughout the span calibration procedure.
Note: The PhD Lite requires a fixed flow rate of 1.0
liter/minute for all calibration procedures.

biosystems PhD Lite Specifications

General

Brand	biosystems
Model	PhD Lite
Category	Security Sensors
Language	English