The electronic instrumentation

In electroanalytical measurements, it is necessary to control the potential of the working electrode, which is usually accomplished by a so-called potentiostat. The potentiostat 

---

In order to keep the book to a manageable size, we did not insert an analogous chapter dealing with electronics. Nevertheless, a chapter about the electronic instrumentation was included in the fourth part. 

The same can be said for the sections concerning the instrumental techniques of GC, IR, NMR, and HPLC. The chromatographic techniques of GC and HPLC are presented as they relate to thin-layer and column chromatography. The spectroscopic techniques depend less on laboratory manipulation and so are presented in terms of similarities to the electronic instrumentation of GC and HPLC techniques (dual detectors, UV detection in HPLC, etc.). For all techniques, the emphasis is on correct sample preparation and correct instrument operation. 

Lubricants. Tellurides of titanium, zirconium, molybdenum, tungsten, and other refractory metals are heat- and vacuum-stable. This property makes them useful in solid self-lubricating composites in the electronics, instrumentation, and aerospace fields (see Lubrication and lubricants). Organic tellurides are antioxidants in lubricating oils and greases. 

Apparatus Design Arising from the Needs of the Electronic Instrumentation... 

The electronic instrumentation necessary for the operation of the proportional counter is shown in Figure 18.6. Pulses from the detector pass through a preamplifier and amplifier, where they are shaped and amplified. Emerging from the amplifier, the pulses go to a discriminator. The discriminator is set so as not to trip on noise pulses but rather to trip on radiation pulses of any larger size. The number of discriminator pulses produced is recorded by the scaler. 

Figure 4.8 shows the differential nonlinearity (left) and the electronic instrument response function (right) of an SPC-134 TCSPC module (Becker Flickl, Berlin) for a different number of DAC bits, Ndac. The nonlinearity curves were recorded by detecting a continuous, unmodulated light signal. The instrument response functions were measured by using 1 ns pulses from a pulse generator at the photon pulse and reference inputs. 

Instrument shop. This shop is primarily for iriaintenance and repair of the electronic instruments used for reactor operations. Tho shop size is such that it also permits some maintenance of electronic instruments used for experiments. Construction of new instruments is beyond the intent or facili--ties of this shop. As with the other shopsi equipment and its layout are placed,within the operating contractor s jurisdiction. 

Cables, wires, and connectors. Remedies light and flexible wires, carefully prepared wire tracks, and wire fixation with small wire loops allowing patient to move without wire pulling the electrode. Each electrode wire before leaving the body could be terminated in a small box, with common cable further from the body up to the electronic instrument. Tiny box with preamplifiers near the patient. Prewired electrodes are without the weight of local connector and plug. 

The fourth source of background noise is the electronic instrumentation. The noise density of the I-U converter is proportional to the square root of its feedback resistance. Therefore, a careful optimization of Rf, in such a way that the high gain and low noise is achieved, must be done when designing the I-U converter [6]. The current noise density of the electronic instrumentation is inversely proportional to the input impedance of the converter. With this respect, the pipette capacity plays an important role in defining input impedance of the I-U converter, and consequently, its noise characteristics. Some practical considerations of... 

Clyde F. Coombs, Jr. recently retired from Hewlett-Packard, where he had worked as an electronics engineer and manager. One of the most successful editors in professional publishing today, he developed and edited all five previous editions of the Printed Circuits Handbook, and also edited the Electronic Instrument Handbook and the Communications Network Test and Measurement Handbook, three of McGraw-Hill s best-selhng technical handbooks. 

An important source of undesired noise is the electronic instrumentation. Measurements are often performed at open circuit. If measurements at a fixed current are desired, the preferred method is to use batteries and wire resistors. Potentiostatic control is more difficult to achieve without injecting noise into the system. A careful discussion of the sources of noise in potentio-stat-ic measurements and the ways of minimizing them was published by Gabrielli and coworkers (Gabrielli et al., 1986). 

At small values of voltage sweep rate, typically below 1 mV/s, the capacity effects are small and in most cases can be ignored. At greater values of sweep rate, a correction needs to be applied to interpretations of ip, as described by Nicholson and Shain. With regard to the correction for ohmic drop in solution, typically this can he handled adequately by careful cell design and positive feedback compensation circuitry in the electronic instrumentation. 

Nanopores represent one the best examples of a cutting-edge technology for which the electronic instrumentation, coupled to a nanodevice, plays a fundamental role [16]. In fact, the performance of the current amplifier. 

This is an order of magnitude less than the limit set by the noise of the nanopore, showing the key role of the electronic instrumentation. Careful design of the nanopore device is therefore required to avoid a dramatic reduction of the useful bandwidth due to a large pore capacitance. In particular, in the case of a solid-state nanopore fabricated on a silicon substrate it is necessary to take into account the stray capacitance added by the conductive substrate. To clarify this aspect, let us consider the simplified device sketched in Fig. 11a based on a free-standing 50 pm x 50 pm membrane in silicon nitride (thickness t = 20 nm) grown on a silicon substrate. 

Viscosity of D2O and uranium solutions. The viscosity of heavy water was measured from 30 to 250°C by Heiks et al. [54]. Good agreement with four values reported by Hardy and Cottington [65] was found. The apparatus used has been described by Heiks et al. [51] and the electronic instrumentation for measuring the time of fall of a plummet containing a radioactive pellet has been described by Rogers et al. [52]. 

---