Vasthi Instruments Back Scattered Dust Monitor for Ideal monitoring opacity and smoke levels in the exhaust gas of industrial combustion or air filtration processes. The instrument’s Back scatter technology means that the ‘telescopic’ detector field of view is controlled to eliminate stray scattering from the far inside stack wall. The back scattered dust monitor is conveniently mounted on one side of the stack and usually requires no light absorber or beam dump on the opposite side of the stack. The optical parts include laser source,power control,photoelectric sensor and scattered light receiving. The 650nm laser beam sent by the laser at a tiny angle into the emission source,where it acts with the dust particles to produce scattered light. The back scattered light will be processed in the sensor into electrical signals. The circuit part will realize the photoelectric conversion,laser beam modulation,signal amplification,demodulation,light source power control, V/I conversion and HMI display. Calibrator is used to generate stable optical signals to zeroing and span calibration of the device. The Back Scattered Dust Monitor design has been implementing the thinking of “no tool” on-side installation , to minimize the complexity of field installation.