Voltage function generator

Mossbauer spectra are usually recorded in transmission geometry, whereby the sample, representing the absorber, contains the stable Mossbauer isotope, i.e., it is not radioactive. A scheme of a typical spectrometer setup is depicted in Fig. 3.1. The radioactive Mossbauer source is attached to the electro-mechanical velocity transducer, or Mossbauer drive, which is moved in a controlled manner for the modulation of the emitted y-radiation by the Doppler effect. The Mossbauer drive is powered by the electronic drive control unit according to a reference voltage (Fr), provided by the digital function generator. Most Mossbauer spectrometers are operated in constant-acceleration mode, in which the drive velocity is linearly swept up and down, either in a saw-tooth or in a triangular mode. In either case. 

A memory sweep is initialized when the MCA receives a start pulse from the function generator at the trigger input (7). The start pulse is synchronized with the sweep of the reference voltage (Vr) for the Mossbauer drive. It opens the first MCA channel when the source velocity passes through the minimum (cf. Fig. 3.3). After this start trigger, a train of 512 channel advance pulses follows with exact delay times of about 100 ps each. On receiving such a channel advance pulse, the... 

The Mossbauer transmission spectra were recorded in the constant acceleration mode with an Elscint Mossbauer drive unit and a model MFG 3A Elscint function generator, an MVT-3 linear velocity transducer and an MD-3 transducer driving unit, y-ray detection was done with a Reuter-Stokes Kv-CH4 proportional counter driven by an Ortec 401A/456 high voltage power supply. Voltage pulses were introduced into an Ortec 142 PC preamplifier and an Ortec 571 spectroscopy amplifier. Data were collected on a Tracor-Northern NS-701A multichannel analyzer. The data were later analyzed on an IBM 360/370 computer. 

This equation suggests that the real electrode potential Ereai can be determined only under conditions where the last term vanishes. Thus, the problem is to correct Emeasured for the Contribution of iRu- This is normally accomplished by a positive feedback circuit incorporated in the potentiostat, which adds a fraction of the current follower output to the voltage provided by the function generator. If the feedback resistance Rf is exactly equal to R , the iRu term in Eq. (56) is compensated for and Emeasured is equal to Ereai- The problem then is the selection of the value of Rf. Although this can be accomplished by direct measurement of Ru and other procedures [2,144], a simpler procedure is desirable for the level of sophistication of most electrochemical studies. Such a simple and convenient method is to adjust the feedback circuit until... 

Testing procedure. The magnetic permeability measurement is performed on the samples formed to the shape of toroids wrapped uniformly with two sets of wire windings. The primary coil is excited with a sine wave from a function generator. The voltage induced in the secondary coil is measured with a lock amplifier at a frequency range of 0.5 Hz to 120 kHz. ... 

Figure 15.7.2 Alternative configuration for use with an ultramicroelectrode. The function generator produces the desired waveform and controls vs. ground, which is — wk the reference electrode. The current at the working electrode is transduced to a voltage using a current follower in the usual manner.

Figure 3, Schematic of the experimental arrangement used to obtain cyclic pressures. Air from the compressor flowed through the reducing valves through the voltage to pressure transducer, then through an adjustable ratio relay to the actuators. The air pressure out of the voltage-pressure transducer was controlled by the voltage input regulated by the function generator. The loads on the tissue and the tissue s displacement were monitored by a strip chart recorder.

With evaporated molecular films, one observes a similar situation [38]. Figure 8.58 gives the characteristic of the unipolar electron current in an Alq3 film at room temperature. The contacts are Ca as electron injector and aluminium as counter electrode. The difference in their work functions generates a built-in voltage Vbi 1V. Only when V> -Vbi does current begin to flow. In the pass direction, at V 4 V, it is already a factor of 10 larger than in the inhibited direction. 

For simple measurements a potentiostat and possibly separate multimeters for voltage and current measurements are adequate. For complicate experiments a function generator, an oscilloscope and a frequency response analyzer should be added to the system. When choosing an instrument one should check its capacity (operating rate, accuracy etc), n aintenance, compatibility with other devices and price. 

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