GAS ANALYSER

FEATURES

• Analyses petrochemical gases
  
• Serial communication to PC
  
• 4 X 4 Matrix Keyboard
  
• Anunciation and management of 4 alarms conditions w/ hysteresis
  
• 1 microampere probe resolution
  
• 3 SSR outputs for soleniod operation
  
• 4 - 20 mA output for Strip Chart recorder
  
• Real time clock and calender
  
• On line UPS
  
• Buzzer for audio alarm
  
• Digital PI Filter for analog data from probe
  
• 16 seg X 8 alpha numeric LED Display
  
• Display Features : Edit, scroll,Blinking
  
• Display Fields :Date, Time, Gas analysis, Upper and Lower thresholds,serial communication status and control, alarm management and status,memory usage.
  

Pipelines in petrochemical plants transport organic and inorganic gases such as ammonia, sulphur dioxide, nitrogen dioxide, phosgene, isopropyl alcohol etc. Concentration of these gases needs to be measured in order to control and monitor the process.

The gas is sensed using a probe which gives a 0-100 uA output. This output is then converted to a voltage in the 0-2.5 V range, using single supply opamps and is compensated for temperature variations using a thermistor.This compensated output is then converted to an 8 bit digital value using an AD 670 converter and is also used to generate a 4 – 20 mA output for a strip chart recorder.

Once the temperature compensated probe data is digitized and read into the SOPC it is filtered in a low pass software filter using the floating point instructions of the CPU core. This filtered value is displayed along with date, time and the units it represents e.g. PPM(parts/million), PCT(percentage), DEG(degrees centigrade),etc. When the value crosses the upper or lower threshold limits, recording of the analog value, along with the units, date and time of occurrence takes place in the internal memory. Simultaneously a buzzer alarm is triggered with a different tone for upper and lower thresholds. Solid state relays turn on which in turn switch ON/OFF pumps, solenoid valves, blowers, reaction vessels, furnaces etc at the plant. When the probe is disconnected a message is displayed and this too turns ON a solid state relay and a buzzer alarm. When the analog value crosses the maximum limit of the analyzer again a solid state relay and a buzzer alarm are triggered.

All alarms are disabled at power ON and during editing of any field. Alarms have to be enabled using the keyboard. Date and time fields are displayed in realtime and can be edited via the keyboard as are settings of threshold (upper/lower) and units of measurement.

The number of records written in the internal memory are displayed along with a message when the memory is full. Data can be transmitted to a desktop computer on which a user program converts the data to tabular and graphic format for archival and printing.

The instrument contains a backup battery and the charging circuitry associated with it.

The Gas Analyzer is implemented as an SOPC on a 30,000 gate count Altera FPGA. It contains the following IP cores – FPU (IP10), RTCC (IP5), Keyboard controller (IP1), ADC interface (IP12), LED display controller (IP20), Serial port (IP4), Bus controller, Wait state generator, internal ROM and RAM, Clock generator, Address decoder, Counters, Ports, Address latch, Control logic and Embedded software.

IP CORES