Model GDA 4508 -Multi Point Sampling System

The GD 4508/16 outputs relative gas level via the Modbus Slave Interface, allowing for BMS control of the air make up of each room relative to external fresh air. Each room is sampled approximately every 10 minutes (dependent on the number of lines and length of lines). The GDA 4508 is placed in an accessible location up to 50M from the filter head; this is the actual sampling point where the sample is being drawn from. The gas is drawn via 6mm ID tubing from the area that needs to be tested and is passed over the sensor element. The end of line filter prevents dust and mycological build up in the line. There is an inbuilt flow fail detector to ascertain that the vacuum pump is operational.

• Flow fail ( blockage ) signal per line (Modbus register)
• Sensor failure signal ( Modbus register)
• Long life dc brushless vacuum pump
• End of line filter to prevent build-up of dust in sample line
• All measurements relative to external fresh air
• Sensor auto-calibrates to fresh air input
• High level Interface to Modbus
• Modbus RTU address selectable
• Readings in Modbus buffers are relative to fresh air measurement not PPM
  • Example
  • external air measurement 500ppm
  • room measurement 1000ppm
  • buffer value (1000/500) x 100 = 200%
    •  if external air gas reading varies so will % in buffer
    • If sensor reading varies then both sides of components of the relative equation vary by the but the relative % will be the same