Multichannel recording

The mass spectrometer is a mass-flow sensitive device, which means that the signal is proportional to the mass flow dm/dl of the analyte, i.e. the concentration times the flow-rate. It is only now possible to realise the high (theoretically unlimited) mass range and the high-sensitivity multichannel recording capabilities that were anticipated many years ago. Of considerable interest to the problem of polymer/additive deformulation are some of the latest developments in mass spectrometry, namely atmospheric pressure ionisation (API), and the revival of time-of-flight spectrometers (allowing GC-ToFMS, MALDI-ToFMS, etc.). 

Some commercially available detectors have a number of detection modes built into a single unit. Fig. 2.4o is a diagram of the detector used in the Perkin Elmer 3D system, which combines uv absorption, fluorescence and conductivity detection. The uv function is a fixed wavelength (254 nm) detector, and the fluorescence function can monitor emission above 280 nm, based on excitation at 254 nm. The metal inlet and outlet tubes act as the electrodes in the conductance cell. The detection modes can be operated independently or simultaneously, using a multichannel recorder. In the conductivity mode, using NaCl, a linear range of 103 and a noise equivalent concentration of 5 x 10 8 g cm-3 have been obtained. 

Array detectors are arrangements of many detector elements, they allow the imaging of objects or multichannel recording of spectra. 

Light emitted by the samples is registered by a general purpose side-on photomultiplier tube (Hamamatsu 1P28, the spectral response from 185 to 700nm, the peak sensitivity at 450 nm),and recorded independently for each of eight cells by a multichannel recorder (Hewlett Packard 7418A)... 

Output signals from the pressure and ultrasonic transducers and from the thermocouples were registered using multichannel recorders (HOUSTON INSTRUMENT, OMNISCRIBE B-5000). 

Figure 5.4 Temperature profile for colored samples as collected from the multichannel recorder (Minnesota 30° backed, July 23, 1991). (According to Fischer, R.M. and Ketola, W.D., ASTM, STP 1202, 1994.)...

A five-sample multiple sample block has also been described by Cox and McGlynn (8). A somewhat different approach was employed by Burr (9) in which five samples, contained in an aluminum block, were recorded using a multichannel recorder. The AT signals of the samples were recorded at 36-sec intervals. 

With the controlled atmosphere heated sample holder, it was a simple matter to connect a thermistor-type thermal conductivity cell to the system and, by means of an external multichannel recorder, record the DRS and the evolved gas detection lEGD) curves simultaneously (17). This modification of the apparatus is shown in Figure 9.4. The cell was connected to a Carle Model 1000 Micro-Detector system by means of metal and rubber tubing. The thermal conductivity cell was enclosed by an aluminum block which was heated to 100 C bv means of a cartridge heater. The block was connected to a preheat chamber, also operated at 100 C, which was used to preheat the helium gas stream before it entered the detector. The output from the detector bridge was led into one channel of a four-channel 0-5 mV Leeds and Northrup multipoint strip-chart potentiometric recorder. The temperature programmer from a Deltatherm III DTA instrument was used to control the temperature rise of the DRS cell. Output from the Beckman Model DK-2A... 

An interesting alternative is the photodiode spectrometer shown schematically in Fig. 16. The monochromator, sometimes also called a polychromator,has only one entrance slit and no moving parts. The beam that is spacially resolved by a fixed grating falls upon a linear photodiode array thus making possible multichannel recording and fast electronic processing. 

Any EEG system consists of electrodes, amplifiers (with appropriate filters), and a recording device. Instrumentation required for recording EEG activity can be simple or elaborate. Note Although the discussion presented in this section is for a single-channel system, it can be extended to simultaneous multichannel recordings simply by multiplying the hardware by the number of channels required. In cases that do not require true simultaneous recordings, special electrode selector panels can minimize hardware requirements.)... 

Edell, D., A peripheral nerve information transducer for amputees long-term multichannel recordings from rabbit peripheral nerves. IEEE Trans. Biomed. Eng., 1986. 33 203-214. 

Recording methods in applied enviromnents make increasing use of new techniques for the acquisition of physiological and psychological data. Portable multichannel recorder/analyzer systems and handheld computers provide new means of ambulatory assessment and foster a more ecologically valid approach to many issues in the applied fields. In this chapter, such developments are reviewed with particular emphasis on ambulatory techniques. 

A. Snellings, D.J. Anderson, and J.W. Aldridge, Use of multichannel recording electrodes and independent component analysis for target localization in deep brain structures. Proceedings of the 1st International IEEE EMBS Conference on Neural Engineering, Capri Island, Italy, 305-308 (2003). 

A minimally invasive microelectrode array intended for high-resolution multichannel recordings of electromyographic signals has been developed [88]. As the structural substrate parylene-C was chosen, the device should be extremely flexible. The steps of fabrication are shown in Figure 2.12. 

A real-time interpretation during the GC/MS run by several classifiers and recording of the classification chromatograms in real-time on a multichannel recorder or display was proposed by Franzen C863. 

The use of multichannel recording systems provides more quantitative analysis of source mechanisms utilizing the digitally stored AE signals. Two methods are in eommon use in source mechanism studies on rock specimens, fault-plane solution method and moment tensor analysis. In earthquake seismology, the classical method is the fault-plane solution... 

A multichannel recorder capable of measuring and recording variable parameters over a period of time provides information on equipment operation as a function of a variable. Typical parameters measured include kilowatts, kWh, temperatures, and, with the use of the ultrasonic flow meter, flow. With this equipment, for example, it is possible to record chiller load and energy use as a function of outdoor air temperature by recording chilled-water supply and return temperature, chilled-water flow, chiller kilowatts, and outdoor air temperature. 

A multichannel recorder is also useful for metering the kilowatt load of air compressors over a period of time. Using compressor manufacturer performance data and observed maximum and minimum load, unloading point, etc., the facility air-load profile can be established. If it is determined to be necessary, a more accurate profile of energy use and air use can be established by incorporating an airflow meter, but this requires the time and expense of installation in the piping. 

Najafi K, Wise KD, Mochizuki T (1985) A high-yield IC-compatible multichannel recording array. IEEE Transactions on Electron Devices 32 1206-1211. 

Each receiver is connected to a common multichannel recording instrument (i.e., a seismograph). This is the most significant difference between the CSW and the MASW techniques, as CSW is usually based on a two-receiver approach. Also the MASW method generally uses an impulsive source, such as a sledgehammer, to produce surface waves, whereas the CSW technique makes use of a frequency-controlled vibrator. 

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