Conversion Gain

The number of discrete parts (channels) into which the input pulse range (0 to -I-10 V) is divided is called the conversion gain. The conversion gain is set by a stepwise control knob located on the front of the instrument. As an example, if the conversion gain is set at 2048 channels, it means that the maximum pulse height (10 V) is divided into that many parts. Therefore, the resolution of the MCA at this setting is... 

The conversion gain may be changed. In the example discussed here, if a peak is recorded in channel 300 with conversion gain of 1024, that same peak will be recorded in channel 150 if the conversion gain is switched to 512. 

There are analyzer models that do not allow change of conversion gain. For such an MCA, if C is greater than the total memory of the instrument, one should return to step 2 and decrease by reducing the gain of the amplifier. 

The number of channels and the range of time intervals analyzed may be changed over a wide range by simply changing the conversion gain of the MCA. 

The resolution of an ADC is expressed in terms of channels. It represents the maximum number of discrete voltage increments into which the maximum input pulse can be subdivided. ADC resolutions range from 4096 to 16,384 channels. Since commercial amplifiers can provide a maximum 10-V pulse, an ADC with a resolution of 4096 channels may subdivide 10 V into 4096 increments. Another quantity used is the conversion gain of the ADC. The conversion gain may be considered as a subset of the resolution. An ADC with a resolution of 16,384 channels may be used, depending on the application, with a conversion gain of 4096, or 8192, or 16,384 channels. 

Eq. 17.2 theoretically stipulates that the more hydrogen is removed the higher conversion of ethane could be achieved. Assuming that the partial pressure of H2 was somehow reduced by 40% in a conventional reactor and using the thermodynamic equilibrium constants for 555°C and 600°C given in Table 17.2, the calculated equilibrium ethane conversions were 23.9% and 37.8% giving respectively about 5% and 7% conversion gains. 

Pulse height spectra for alpha bombardment were collected by affixing an alpha source to the end of the detector retention tube, facing the detector, at approximately 1 cm distance. The source used was a 1.0 pCi Am disk source mounted in the end of a ThorLabs optics tube. Counts were accumulated for a live time of250 s. The MCA conversion gain was set at 256 channels. 

For a parametric sonar receiver in water, the insertion of a polydimethyl-siloxane cylinder in front of the receiver improved the parametric conversion gain by 20 dB and reduced the beam width by a factor of 2-3 (37). 

ADC conversion gain is simply the number of channels actually used in a particular application - in everyday parlance, the spectrum size. It is possible, of course, for an MCA to have a 16k ADC but the user opts to use only 8k or 4k. With a conversion gain of 4k, pulses... 

Choose an ADC conversion gain such that the FWHM is spread over about four channels. For many purposes, 4096 channels will be appropriate. 

It is first necessary to decide on the energy range required and from that the appropriate conversion gain (i.e. spectrum size). In Chapter 4, Section 4.6.8, it was explained that the optimum spectrum size is a balance between sufficient channels within the peaks of interest to aid computer deconvolution of peaks, bnt not so many that the statistical uncertainty on each channel snffers. The relationship in Equation (11.1) was snggested ... 

CONVERSION GAIN of an ADC is the number of channels used in a particular spectrum acquisition. Usually a binary multiple of two. 

REACTOR OUTLET TEMPERATURE — the higher the value, the higher the conversion. Table 2 shows a 5 Wt % FF conversion gain for a 43 F increase in riser outlet temperature. 

At the termination of the riser it is important to have quick separation of reaction mix from spent catalyst. After the riser, the reaction mix can remain in the reactor vessel for over 20 seconds before it enters the reactor cyclones and is separated from the spent catalyst. Typically, catalyst densities between riser outlet and cyclone inlet average only 1 to 3 Lb/Ft. During that 20+ seconds additional conversion can occur, but since the catalyst is spent the conversion is thermal in nature and not selective to gasoline. Ross (1990) reports commercial information (Figure 15) for a simple riser turndown that shows a 4 LV % FF conversion gain between riser outlet and cyclone inlet. Even though conversion increased, gasoline yield went down. 

In the digital domain, these conversion gains can be reported as quantization step equivalents (QSE) these have units (for example) of counts per photon, counts per irradiance unit, or counts per ampere. A single count (a.k.a least significant bit or LSB) is called the step size and is usually reported as microvolts or millivolts per count. 

One or two microseconds later the discharge process starts. The slope of the linear approach to zero depends on Che conversion gain. A few hundred mlllvolCs below zero,... 

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