Electronic modulation

Intelligent transmitters have two major components (1) a sensor module which comprises the process connections and sensor assembly, and (2) a two-compartment electronics housing with a terminal block and an electronics module that contains signal conditioning circuits and a microprocessor. Figure 6.9 illustrates how the primary output signal is compensated for errors caused in pressure-sensor temperature. An internal sensor measures the temperature of the pressure sensor. This measurement is fed into the microprocessor where the primary measurement signal is appropriately corrected. This temperature measurement is also transmitted to receivers over the communications network. 

Ceramic boards are currently widely used in high-performance electronic modules as interconnection substrates. They are processed from conventional ceramic precursors and refractory metal precursors and are subsequently fired to the final shape. This is largely an art a much better fundamental understanding of the materials and chemical processes will be required if low-cost, high-yield production is to be realized (see Chapter 5). A good example of ceramic interconnection boards are the multilayer ceramic (MLC) stractures used in large IBM computers (Figure 4.11). These boards measure up to 100 cm in area and contain up to 33 layers. They can interconnect as many as 133 chips. Their fabrication involves hundreds of complex chemical processes that must be precisely controlled. 

The second field-cycling method (65-67) uses electronic modulation of the current flowing through the coil of an electromagnet. This technique, commonly called Phst Field Cycling (FFC) NMR relaxometry, permits much faster variations of the field induction and thus extends the applicability of the field cycling approach to very short relaxation times Ti, at present, down to fractions of a millisecond. 

EPR spectra were recorded with a Varian E9 X-band spectrometer using field (100 kHz) and light (13 or 83 Hz) modulation with phase-sensitive detection at the modulation frequencies (19). Typically, the field modulation amplitude employed ranged from 20 to 40 gauss, the microwave power from 0.1 to 0.5 mW. Measurements were performed on frozen solutions of the porphyrins at about 100 K using the standard Varian variable temperature accessory or at about 10 R with an Oxford Instruments helium gas cryostat. Light sources used for photoexcitation were a 1000 W Xe arc source powered by a Photochemical Research Associates Supply with electronic modulation... 

Fig. 28. Schematic for LC polyester thin film solid state processing of multichip electronic modules...

Electronic modules are the industry standard for controllers employing a wide range of control strategies. Although, more recently, there has been rapid development of microprocessor-based controllers (see Sections 7.20 and 7.21) where control actions are simulated using software, hard wired systems based upon the integrated circuit (IQ and operational amplifier (op-amp) are still much in evidence. 

Cotton also investigated the use of ellipticity measurements for CD studies. The combination of a linear polarizer and a Fresnel rhomb was used by Cotton to produce polarized light which could vary in its orientation from circular to elliptical. A second linear polarizer was then used to monitor changes in the orientation of the major axis of the ellipse which occurs as a result of the CD. In addition, the apparatus could also be used to measure optical rotation (circular birefringence). The experimental simplicity of this approach relative to his other system allowed more sensitive measurements to be made. This experimental simplicity also served as an impetus for other researchers in the field, and the ellipticity approach dominated the available technology from the time of Cotton s first efforts to the 1960 s, when electronically modulated systems were developed. 

Figure 1. Bruker EM 640S modular GC/MS system A - mass spectrometer, B - split/splitless injector, C -GC module, D - gas supply, E - electronic module, F -ruggedized PC, G - Printer, H - external power supply...

The installed software package also contains the AMDIS libraries onsite.cls and onsite.isl for calibration, test, and internal standard compounds (see Section 2.2). After software installation the hard disks are assigned to a particular GC/MS system. Since each instrument (defined by serial number) may be combined with any of the 5 electronic modules, 12 GC modules and 10 injector modules in possession of OPCW the actual instrument configuration needs to be defined. This is achieved by installing configuration files for the... 

The principle of operation of the EM method is shown in Figure 10. The basic instrument consists of two coils and an electronics module. The transmitter coil is separated from the receiver coil by a specified distance. When energized, the transmitter coil induces circular eddy current loops into the... 

These two examples show that Av is very much smaller for homonuclear double resonance, suggesting a simple way to generate v2. Instead of using a separate rf oscillator, we can use part of the output from the v, channel electronically modulated with an audio-frequency signal to generate output at v2. This technique makes it easier to control the exact value of Av and to focus v, and v2 exactly where we want them. 

Figure 8.1. (A) CETAC ultrasonic nebulizers U-5000AT+ (1-15) and U-6000AT+ (1-19). 1 — transducer, 2 — aerosol chamber stand, 3 — aerosol chamber, 4 — sample/rlse adapter, 5 — U-tube, 6 — heat cords, 7 — glassware module, 8 — transducer radio frequency (RF) cable, 9 — sample inlet tubing, 10 — electronics module, 11 — auxiliary rinse port, 12 — operate switch, 13 — fast pump switch, 14 — heater controller (nebulizer), 15—cooler controller (nebulizer), 16 — heater controller (desolvator), 17 — flow meter, 18 — flow control and 19 — membrane desolvator controller. (B) Detailed scheme of the U-6000AT+ glassware module. (Reproduced with permission of CETAC Technologies.)...

Tang, L., Moores, K.A., Ramaswamy, C. and Joshi, Y., 1998, Characterizing the Thermal Performance of a Flow Through Electronics Module (SEM-E Format) Using a Porous Media Model, IEEE Fourteenth IEEE SEMI- THERMTM Symposium. 

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