Hardware Description - Hach ORBISPHERE K1200 User Manual

Specifications
The oxygen partial pressure (pO
( to build the sensor calibration curve (shown right in
Stern-Volmer equation (shown left in
mbar
a constant and 
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
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 outputs are frozen for 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
-1
) representing the quenching efficiency of the oxygen and thus the sensor sensitivity, f
is the phase-shift at zero oxygen representing the unquenched fluorescence
0
Figure 3 Stern-Volmer equation and calibration curve
) is then linked to the corresponding phase-shift measurement
2
Figure
Figure 3) where K
sv
. The dissolved oxygen concentration is
sv
3). This curve is described by the
is the indicator quenching constant (in
is
0