Mettler Toledo Gas Analytics launches its cross-pipe GPro 500 TDL gas analyzer. Most TDLs consist of two parts, a laser source and separate receiver with a photodiode that analyzes the laser light after it has passed through the gas sample. An issue with TDL sensors is the requirement for maintaining very accurate alignment between the two parts. TDL designs with laser and sensor elements placed across the stack are appreciated when wider stacks cause differences in concentration across the diameter. 

Mettler Toledo’s GPro 500 series of TDLs combines both parts into a single unit. A probe attached to the sensor features a corner cube at its end that redirects the laser beam back to the sensor; therefore, loss of alignment is not possible, according to the company. Mettler Toledo’s Cross-Pipe GPro 500 is designed for wider stacks where gas concentration is not constant. A newly developed, two-dimensional corner cube array is positioned in the pipe, opposite the analyzer head. Exact alignment is not required. As long as there is a straight path between the two parts, the laser will hit the array and the beam will be directed back to the photodiode in the analyzer.