Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Voltage feedback, instrumentation

Fig. 4. Impedance converters for measuring e.m.f. of a cell, (A) using a voltage follower (the effective input resistance, equals the common mode resistance of an FET-type operational amplifier), (B) using voltage feedback (Reff R-Ao, where R is the input resistance, Aq is the OA gain without feedback), (C) by means of an instrumentation amplifier (typical differential gain A = 1 + lO /Re t)- Abbreviations OA, operational amplifier AZ OA, automatically zeroed OA lA, instrumentation amplifier S, shielding. Fig. 4. Impedance converters for measuring e.m.f. of a cell, (A) using a voltage follower (the effective input resistance, equals the common mode resistance of an FET-type operational amplifier), (B) using voltage feedback (Reff R-Ao, where R is the input resistance, Aq is the OA gain without feedback), (C) by means of an instrumentation amplifier (typical differential gain A = 1 + lO /Re t)- Abbreviations OA, operational amplifier AZ OA, automatically zeroed OA lA, instrumentation amplifier S, shielding.
In fact, we don t monitor two variables through the same electrode. Instrumentally, we employ a feedback loop within the voltage source... [Pg.135]

Fig. 1.36. The topografiner. An instrument developed by Young, Ward, and Scire in the late 1960s, which is the closest ancestor of the STM. (a) The tip is driven by the x and y piezos, and the sample is mounted on the z piezo. By applying a high voltage between the tip and the sample, a field-emission current is induced. Using the field-emission current as the feedback signal, topography of the sample surface is obtained, (b) Close-up of the tip and the sample. The end of the tip has a small radius, typically a few hundred A. The typical tip-sample distance is a few thousand A. (After Young, 1971.)... Fig. 1.36. The topografiner. An instrument developed by Young, Ward, and Scire in the late 1960s, which is the closest ancestor of the STM. (a) The tip is driven by the x and y piezos, and the sample is mounted on the z piezo. By applying a high voltage between the tip and the sample, a field-emission current is induced. Using the field-emission current as the feedback signal, topography of the sample surface is obtained, (b) Close-up of the tip and the sample. The end of the tip has a small radius, typically a few hundred A. The typical tip-sample distance is a few thousand A. (After Young, 1971.)...
One source of noise of this type is the slow drift in the radiant output of the source. This type of noise can be called source flicker noise (Section 5B-2). The effects of fluctuations in the intensity of a source can be minimized by the use of a constant-voltage power supply or a feedback system in which the source intensity is maintained at a constant level. Modern doublebeam spectrophotometers (Sections 13D-2 and 13D-3) can also help cancel the effect of flicker noise. With many instruments, source flicker noise does not limit performance. [Pg.181]

See other pages where Voltage feedback, instrumentation is mentioned: [Pg.233]    [Pg.322]    [Pg.304]    [Pg.182]    [Pg.176]    [Pg.203]    [Pg.924]    [Pg.641]    [Pg.376]    [Pg.167]    [Pg.322]    [Pg.148]    [Pg.76]    [Pg.86]    [Pg.2972]    [Pg.344]    [Pg.44]    [Pg.131]    [Pg.156]    [Pg.305]    [Pg.652]    [Pg.317]    [Pg.87]    [Pg.96]    [Pg.282]    [Pg.484]    [Pg.167]    [Pg.104]    [Pg.18]    [Pg.285]    [Pg.69]    [Pg.354]    [Pg.24]    [Pg.631]    [Pg.376]    [Pg.381]    [Pg.352]    [Pg.86]    [Pg.48]    [Pg.97]    [Pg.44]    [Pg.457]    [Pg.87]    [Pg.94]    [Pg.102]    [Pg.119]    [Pg.243]   
See also in sourсe #XX -- [ Pg.639 ]



SEARCH



Feedback voltage

© 2024 chempedia.info