CH 100 pages

CH-10

The modulating frequency range of the CH-10 chopper is from 10 Hz to1 kHz, fixed at any one value within the range. The aperture is inversely proportional to the frequency, and is a function of the size of the vanes and the type (duty cycle). Operation at the natural resonant frequency is sustained by a feedback amplifier, the AGC driver or the ED driver, supplied separately. The driver controls the aperture and provides a reference signal. The PLD-1C driver will phase lock the device to an external stable source. The PLD-2C driver will lock two choppers in a master/slave mode. The most common type of aperture is the half open in the rest position, 90% duty cycle. It is used for a large beam diameter. When the modulator is operating in this configuration the maximum aperture is produced. The vanes are factory adjusted so that when fully illuminated the maximum excursion condition (controlled by the drive electronics) generates an almost complete sine wave as shown in figure 1.B. Typically, the light is transmitted for 90% of each cycle. The 50% duty cycle modulation is used for a small beam diameter, shown in figure 1.A. The vanes are factory adjusted to be just closed in the rest position. Full aperture for 50% duty cycle is one half of the 90% duty cycle. Balanced operation and high "Q" insure frequency stability, low electrical drive power and low reaction forces. High flexural stiffness provides good resistance to shock and vibration. The standard operating temperature is -40 ↑ CH-10 Tuning Fork Chopper >

Features

One fixed frequency from the range of 10 Hz to 1 kHz Aperture up to 10mm Small size/lightweight Withstands shock and vibration Low power drive electronics Rugged, no wearing parts Maintenance free High reliability High frequency stability (to 0.005%) High amplitude stability <.01% Vacuum operation (to 10- >
10 Torr) >
1 High/low temperature operation (Cryo to 200 >
o C) >
1 o C to +65 >
o C. Jitter free operation Tuning fork choppers are cryogenic and high temperature (200 No radiated electromagnetic interference (EMI) >
o C) capable. They can be constructed of low outgassing materials for ultra high vacuum (10 Reference signal available >
-10 torr) applications. Metal vanes are standard, mirrors, prisms or lenses optional >
1 Tuning fork choppers are especially suitable for long life, dedicated applications, OEM, built into an instrument/system, and for portable systems. Single vane for alternate beam chopping >
1 1 Available as a special order Applications include: test equipment, noise detection (with a lock-in amplifier), pollution and gas detection, radiometry, radiation pyrometry, military, scientific, environmental and aerospace and atmospheric research, non-invasive medical research and laboratory research. Scitec Instruments FIXED FREQUENCY resonant optical modulator is an electromagnetically driven tuning fork device, which uses vanes of different shapes and surface characteristics, attached to moving tines, to chop a light beam with a sinusoidal motion. A range of factory set fixed frequency modulation waveforms (sine, half sine and pulse) is available. >
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