Chopper window

The Transport Controls (see Figure 1.6) operate like standard media file playback or VCR controls. These buttons are used to move the timeline cursor around on the timeline and to control playback and recording in a project. A few transport controls are also available in the Explorer and Chopper windows (defined later). 

The Chopper window (see Figure 1.16) is almost a miniature audio editing tool that allows you to trim audio files. It is completely non-destructive, meaning that changes you make in the Chopper do not change the original source file in any way. The Chopper allows you to quickly and accurately select shorter sections of a media file and then insert these sections into a track as events. 

A waveform is a visual representation of a sound file. Waveforms are visible in ACID in events, in the Chopper window, and in the Track Properties window, among other places. Ultimately, editing in ACID is done by ear, but you can make very precise cuts, splits, and trims simply by looking at the peaks and valleys of the waveform picture of a media file or event... 

The Chopper window is a special tool that is used to perform precise trims of media files and insert the trimmed portion into the timeline. The advantage to using the Chopper to trim events is that you can trim an event in more detail in the Chopper window without zooming in on the project timeline. There are also a number of other tools in the Chopper window that make trimming easier. 

To view the Chopper window, from the View menu, select Chopper or press Alt+2. The Chopper window displays the entire media file of the selected track. Click on a different track to load a different media file into the Chopper. To trim and insert events into the timeline using the Chopper ... 

Drag the mouse on the waveform in the Chopper window. A selection region is created and highlighted. 

You can see in Figure 2.18 that the selection area in the Chopper window is also highlighted on the main timeline, representing the location of the event to be inserted. 

The selected area in the Chopper window is inserted into the timeline at the timeline cursor s position. 

The Chopper window has a short timeline that covers the dnration of the media file. 

Position the main UI timeline cursor where you want the insert to occur. The selection area and arrow from the Chopper window are represented on the main UI timeline at the timeline cursor position. 

The media file is broken up into individual regions, however, and these can be accessed from the Chopper window. 

The various regions can thus be inserted into the loop region using the Chopper window ... 

The Chopper window can be used to insert regions (takes) into the timeline. 

Many Keyboard Navigation and Selection shortcuts also work in the Chopper window, in addition to some playback (transport) controls and zoom shortcuts. 

Fig. 10. LS photometer60 for use at = 1086 nm A - laser, B - lens, C - shutter, D -rotating chopper, E - shutter, F - entrance window, G - thermostat vessel, H - metal shield, I - shutter, J - thermostat liquid, K - cylindrical LS cuvette, L - light trap, M - shutter,...

Figure 3 shows one of our photoacoustic cell for X-ray spectroscopy of solid samples The cylindrical cell has a sample chamber at the center with volume of 0.16 cm which has two windows of beryllium (18 mm x 0.5 mm thickness). A microphone cartridge is commercially available electret type (10 mm ) and the electronics of preamplifier for this microphone is detailed elsewhere Figure 4 shows the typical experimental setup for spectroscopic study X-ray was monochromated by channel cut silicon double crystal (111) and ion chamber was set to monitor the beam intensity. Photoacoustic signal intensity was always divided by the ion chamber current for the normalization against the photon flux. X-ray was modulated by a rotating lead plate (1 mm thick) chopper with two blades. 

In this system the optical filters are combined to form the optical window through which the IR light enters the cell. Passing the chopper wheel modulates the light, but this chopper wheel is perforated at different distances from the center. When rotating the chopper wheel at constant velocity, three different modulation frequencies are obtained-corresponding to the three optical filters. A microphone picks up the photo-acoustic signal downstream. 

A remarkable adaptation of technology borrowed from another analytical method was demonstrated for an electrospray ionization (ESI) IMS instrument ion injection to a drift tube was achieved through modulation with a mechanical chopper as found in atomic absorption spectrometry. The chopper was a disk with a small hole that would align with the source and drift tube and would operate as an ion injector. The disk had a second window that was used with optical sensors to synchronize ion injection and drift time, and ion injections were made at pulse rates of 5 to 200 Hz with pulse widths of 200 to 500 ps. 

The drift tube dimensions or characteristics were as follows length of 45.0 cm, a voltage divider with 3.34-Mft resistors, electric field of about 400 V/cm, and 78 drift rings (0.12 cm thick, 4.90 cm outside diameter, 2.55 cm inside diameter). The front flange of the drift tube was placed at ground potential, and the detector, and housing of the drift tube, was floated to -20.0 kV. Thus, the capillary of the ESI source was operated only at +5.0 kV with +500 V applied to the chopper wheel. The distance between the ESI source and inlet window of the chopper was 2 mm, and that between the inlet window and inlet flange of the drift tube was 5 mm. 

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