The Experimental Study on Detection of Dust Concentration by Back Scattering Method

The result of the experiment using Labview real-time data acquisition and analysis, and considered the backward scattering Angle, detection range, chopper modulation frequency and test factors, thus draws the dust concentration and the relationship between the voltage detection. The results show that the modulation frequency up to 145 HZ, backward scattering Angle as close to ,the detection range as far as possible close to the flue, dust concentration and detection voltage can better meet the linear relationship for the future, it improves industrial smoke concentration on-line measurement provides a basis for the application.

HIGH LINEARITY 8-BIT VCO-BASED CASCADED ΣΔADC FOR DIGITAL DC-DC CONVERTERS

This paper presents the design and implementation of a high resolution voltage-controlled oscillator (VCO)-based ΣΔADC for digital DC-DC converters. The proposed ADC adopts a robust VCO and a sixth-order delta-sigma modulation to attenuate the phase noise and output ripples. The delta-sigma modulation is realized using a cascade of a second-order high-pass filter and a fourth-order band-stop noise shaping filter. Chopper modulation is further employed to reduce the effect of 1/f noise. These have significantly increased the signal-to-noise+distortion ratio (SNDR) and lead to high linearity. The proposed ADC was designed and fabricated using CMOS 0.18 μm process. From measurement, the differential and integral nonlinearities of the ADC are determined to be ±0.5 LSB and ±0.65 LSB, respectively. The SNDR of the ADC is 49 dB up to 500 kHz, which gives an ENOB of 8 bits and quantization step of 2 mV. The ADC also features a low power consumption of 120 μA and a small IC area of 0.18 mm2.

Step Scan Interferometry in the Mid-Infrared with Photothermal Detection

A medium resolution mid-infrared FT-IR instrument (IBM Instruments IR 44) has been modified to do step scanning; this has been done with the use of concepts previously applied to both near- and far-infrared instruments. In this paper we illustrate the method used for driving the mirror in the step scan mode and present some preliminary results from using the instrument with photothermal detection. At the current state of development, results obtained with the use of phase modulation indicate that this method produces significantly higher signal-to-noise ratios than does the use of amplitude (chopper) modulation to generate the photothermal signal.