Hardware Description - Hach ORBISPHERE G1100 User Manual

Specifications
The oxygen partial pressure (pO
( to build the sensor calibration curve (shown right in
by the Stern-Volmer equation (shown left in
quenching constant (in mbar
sensor sensitivity, f
unquenched fluorescence decay time of the dye. The calibration curve thus relies on two
parameters: the phase-shift at zero oxygen and the luminescent spot sensitivity, K
dissolved oxygen concentration is then calculated with Henry's law using the water solubility
curve as a function of the temperature.

2.3 Hardware description

The instrument hardware is made of one main board, and one measurement board for the
measurement channel (= the sensor).
The main board includes the controls for power, display, the touch screen, the barometric
sensor, the alarms, and communication ports. The measurement board performs measurements
and executes commands from the main board. It holds the "Analog output" and "Relays" that
send information to external systems.
A hardware watchdog is activated at program start up, to check that the system is not frozen
(i.e. infinite loop, system crash, etc.). If the watchdog is not refreshed by the software every
minute, the measurement display, the relays and the analog output are frozen up to 2 minutes.
Then the reset shuts down the instrument for 10 seconds and the start-up procedure is
performed. At the same time all the hardware (sensor, measurement board) are reset.
16
) is then linked to the corresponding phase-shift measurement
2
-1
) representing the quenching efficiency of the oxygen and thus the
is a constant and 
is the phase-shift at zero oxygen representing the
0 0
Figure 3 Stern-Volmer equation and calibration curve
Figure 3 below). This curve is described
Figure 3 below) where K is the indicator
sv
. The
sv