Teledyne BDS 3000, Operating Instructions Manual

Page: 29 / 100

Oxygen Analyzer Operational Theory
Teledyne Analytical Instruments
15
2.4 Electronics and Signal Processing
T he Model BDS 3000 Oxygen Analyzer uses an 8031
m icrocontr ol l er wi th 32 kB of RAM and 128 kB of ROM to cont rol all
signal processi ng, i nput / output, and di splay functi ons f or the analyzer .
S ystem power is suppli ed fr om a universal power suppl y module desi gned
t o be compat i bl e wi t h any i nt er nat ional power source. F i gure 2- 7 shows
t he l ocati on of t he power suppl y and the mai n el ect roni c P C boards.
The signal processing electronics including the microprocessor,
analog to digital, and digital to analog converters are located on the
motherboard at the bottom of the case. The preamplifier board is
mounted on top of the motherboard as shown in the figure. These boards
are accessible after removing the back panel. Figure 2-8 is a block
diagram of the Analyzer electronics.
In the presence of oxygen the sensor generates a current. A current
to voltage amplifier converts this current to a voltage, which is further
amplified in the second stage amplifier.
The output from the second stage amplifier is sent to an 18 bit
analog to digital converter controlled by the microprocessor.
The digital concentration signal along with input from the control
panel is processed by the microprocessor, and appropriate control
signals are directed to the display, alarms and communications port. The
same digital information is also sent to a 12 bit digital to analog
converter that produces the 4-20 mA DC and the 0-1 VDC analog
concentration signal outputs, and the analog range ID outputs.
Signals from the power supply are also monitored, and through the
microprocessor, the system failure alarm is activated if a malfunction is
detected.