Reference voltage

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... 

In the first case we have the ideal situation, with no intervening trace resistances considered. So since the reference voltage is 1.25V, we have chosen lkQ and 3kQ resistors to get an output of 5V. Note that the classical equation of a divider is... 

A microcontroller board for sensor read-out was developed in collaboration with AppliedSensor (Reutlingen, Germany). This board provides the power supply and the necessary reference voltages and currents to the sensor chip. The sensor chip is mounted on a socket and connected to the microcontroller. The microcontroller provides a set of commands for programming and reading the on-chip registers, controller parameters and sensor values. The microcontroller also manages the data transfer between the f C interface of the microchip and a serial RS-232 interface for external read-out via a PC. The data stream is continuously read out in the measurement mode. Each data set contains the temperature of the microhotplate, the chip... 

Fig. 5.9. Membrane temperature, Tm, vs. reference voltage, Vr. The reference voltage is given in digital code. The full range of digital values from 1 to 1023 corresponds to a temperature range ofl70°Cto 310 °C...

The features of the monoHthic integrated sensor systems have not yet been fully exploited. The almost linear relationship between input reference voltage and microhotplate temperature renders the systems suitable for applying any temperature modulation protocol. Due their compatibility with other CMOS-based chemical sensors the microhotplates can be also combined with, e.g., polymer-based mass sensitive, calorimetric or capacitive sensors. The co-integration with such sensors can help to alleviate problems resulting from cross-sensitivities of tin-oxide based sensors to, e.g., volatile compounds such as hydrocarbons. A well-known problem is the crosssensitivity of tin oxide to humidity or ethanol. The co-integration of a capacitive sensor, which does not show any sensitivity to CO, could help to independently assess humidity changes. 

We have already anticipated that in a power supply of the type represented by Fig. 12, the current and the field B t) are linearly related to the reference voltage V et only when the device operates in the linear region, clear of saturation. The power supply attains the saturation limit when ... 

Voltage window estimated from cyclic voltammograms contained in the reference. Voltage window may be limited by impurities. 

Three measurements of the breadboard were taken in order to correlate to the SPICE results. Figure 5.4a is a plot of the current regulator s turn-on, Fig. 5.5a is a plot of the load current response to a stepped reference voltage, and Fig. 5.6a is a plot of the current regulator loop. The IsSpice results of these measurements are shown in Figs. 5.4b, 5.5b, and 5.6b, respectively. 

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