Teledyne 3000ZA2G - Zirconium oxide analyzer - Manual (Page 24)

Operational Theory 3000ZA2G
Teledyne Analytical Instruments 12
These boards are accessible after removing the enclosure cover. Figure
2-5 is a block diagram of the analyzer electronics.
In the presence of oxygen the zirconia sensor generates a
logarithmic response in the mV range and is passed to an amplifier. The
output from the amplifier is sent to an 18 bit analog to digital converter
controlled by the microprocessor.
The high operating temperature of the ZrO
2
sensor is required for
proper operation of the sensor. The amplifier PCB contains a circuit that
drives the heater embedded in the sensor. The voltage across the heater
rises slowly to avoid damaging the heater/sensor assembly. After a few
minutes, the sensor will be at the proper operating temperature.
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
digital information representing the output from the sensor is linearized
by the Model 3000ZA2G software and passed to a 12 bit digital to
analog converter that produces the 4-20 mADC 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.