Scanning voltage

D/A converters to generate raster. scan voltages. An important point to be noted is that D/A converters have finite step sizes. A typical D/A converter has a full range of 10 V, with 12-bit accuracy. Each step is 20 V/4096=4.88 mV. By using it directly to drive the x, y piezo with a typical piezo constant of 60 A/V, each step is about 0.3 A. If amplification is installed, the step size becomes larger. 

Optical Multichannel Analyzer System (OMA 2). The OMA 2 system consisted of a PARC Model 1215 console, two PARC Model 1254 SIT detectors, two PARC Model 1216 detector controllers, and a PARC Model 1217 flexible disc drive. The SIT detector is controlled by the 1216 detector controller, which provides both power and scanning voltages and processes the signal for transmission to the OMA 2 console. The OMA 2 console performs all necessary control functions, data acquisitions, data processing and storage of spectra. The system can store 250 (500 points) spectral curves when equipped with the Model 1217 flexible disc drive. 

In operation, the linear-scan voltage generator sweeps the potential between the reference and working electrodes, and the current in the cell is monitored by op amp C. The output voltage of op amp B, which is proportional to the current I in the cell, is recorded or acquired by a computer for data analysis and presentation. ... 

X-scan voltage is then ramped, causing the tip to move in the x-direction but not in the -direction. 

The signal source is a linear-scan voltage generator similar to the integration circuit shown in Figure 3-16c. The output from this type of source is described by Equation 3-22. Thus, for a constant dc input potential of E-i, the output potential given by... 

Fig. 5.16a,b. Field emission scanning electron microscopy of APS-150. a Inside surface and outside surface (scanning voltage 15 kV). b Distribution of pore diameter determined by FE-SEM. Reprinted from [28]. Copyright 2002, with kind permission from Elsevier... 

Scan rates typically vary from 10 mV/s to 1 V/s. The lower limit is due to thermal convection, which is always present in an electrolyte. To record faster responses, an oscilloscope or fast transient recorder used to be required all modern potentiostats operate at fast scan voltages. The limit is determined by the sampling rate and the rise time of the op-amps. The currents in successive scans differ from those recorded in the first scan. For quantitation purposes, the first scan should always be used. 

SVM Scanning Voltage Microscopy Force Microscopy. Springer, Berlin... 

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