Sampling rates

Then, when the digitizer samples the signal, the phase to be used for signal demodulation is known exactly. The FIFO memory is added because the output sample rate of the digitizer is between 8 and 64 kHz (depending on the bandwidth) and the output sample rate of the DSP (of the demodulator) is 5 kHz maximum. So, during one demodulation cycle, many points are written in the FIFO by the digitizer. The DSP reads them and the demodulation is carried out. 

The ultrasound system should have more independent channels and allow the transmitter pulse to be individually adjustable in width and amplitude, and an increased frequency range for the logarithmic amplifier was desired. The digitization should be improved both with respect to sampling rate and resolution. 

The evaluation of the deconvolution results show that time resolution is better or equal to 1 with the chosen processing time unit of 0.08 microseconds (respectively a rate of 12.5 MHz). First signals processed conservatively have been acquired with a samplerate of 12.5 MHz. A Fourier analysis shows that the signals spectras do not have energy above 2.0 MHz. This means that a sampling rate of 4.0 MHz would have done the job as well. Due to the time base of the ADC an experimental check with a sample rate of 5.25 MHz has been carried out successfully. 

Injector The sample, typically 5-200 )J,L, is placed in the carrier stream by injection. Although syringe injections through a rubber septum are used, a more common means of injection is the rotary, or loop, injector used in ITPLC and shown in Figure 12.28 of Chapter 12. This type of injector provides reproducible injection volumes and is easily adaptable to automation, a feature that is particularly important when high sampling rates are desired. 

The carrier stream consists of an acidic solution of Hg(SCN)2 and Fe +. When a sample containing chloride is injected into the carrier stream, the chloride displaces the thiocyanate from Hg(SCN)2. The displaced thiocyanate then reacts with Fe + to form the reddish colored Fe(SCN) + complex, the absorbance of which is monitored at a wavelength of 480 nm. Sampling rates of approximately 120 samples/h have been achieved with this system. 

Finally, FIA is an attractive technique with respect to demands on time, cost, and equipment. When employed for automated analyses, FIA provides for very high sampling rates. Most analyses can be operated with sampling rates of 20-120 samples/h, but rates as high as 1700 samples/h have been realized. Because the volume of the flow injection manifold is small, typically less than 2 mb, consumption of reagents is substantially less than with conventional methods. This can lead to a significant decrease in the cost per analysis. Flow injection analysis requires additional equipment, beyond that used for similar conventional methods of analysis, which adds to the expense of the analysis. On the other hand, flow injection analyzers can be assembled from equipment already available in many laboratories. 

An optimum response was defined as the greatest sensitivity, as determined by the measured potential for a standard solution of penicillin, and the largest sampling rate. The results of the optimization studies are shown in the following... 

The field of view (FOV) is dependent on the quadrature sampling rate, T, during the appHcation of G and the magnitude of G ... 

A = sampling rate (e.g., number of samples per second) The Fourier transform and inverse transform are... 

The resolution of the analog I/O channels of the controller vaiy somewhat, with 12-bit and 14-bit conversions quite common. Sample rates for the majority of the constant sample rate controllers range from I to 10 samples/second. Hard-wired single-pole, low-pass filters are installed on the analog inputs to the controller to protect the sampler from aliasing errors. 

Measurements to determine volumetric flow rate usuaUy require approximately 30 min. Since sampling rates depend on stack-gas velocity, a preliminaiy velocity check is usuaUy made prior to testing for pollutants to aid in selecting the proper equipment and in determining the approximate sampling rate for the test. 

When the operating conditions are uniform and steady (there are no fluctuations in flow rate or in concentration of CO in the gas stream), the continuous sampling method can be used. A sampling probe is placed in the stack at any location, preferably near the center. The sample is extracted at a constant sampling rate. As the gas stream passes through the sampling apparatus, any moisture or carbon dioxide in the sample gas stream is removed. The CO concentration is then measured by a nondispersive infrared analyzer, which gives direct readouts of CO concentrations. 

Recently it has been shown that rotating coiled columns (RCC) can be successfully applied to the dynamic (flow-through) fractionation of HM in soils and sediments [1]. Since the flow rate of the extracting reagents in the RCC equipment is very similar to the sampling rate that is used in the pneumatic nebulization in inductively coupled plasma atomic emission spectrometer (ICP-AES), on-line coupling of these devices without any additional system seems to be possible. 

Contaminant Principle Apparatus Collecting agent Sampling rate (l/min) Collection efficiency (%) Remarks... 

Poisoning of Pellistor by, e.g., silicones, halocarbons, leaded petrol Too high a sampling rate (causing cooling of the elements)... 

The choice of absorbing solution, the strength (normality or pH) of the solution, the sampling rate (generally 1 to 3 liters per minute), and the size of the bottle (20 cc, 50 cc, or 125 cc), are some of the variables which must be considered in using bubblers. 

The sampling rate must be maintained at 1 liter per minute. Sampling at a higher rate may elutriate the solvent vapors from the first section, in which case they may be adsorbed in, or even elutriated from, the second section. 

Sampling duration The period of time that sampling takes place at a specified sampling rate. 

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