Strip chart recorders

The signal emerging from the detector of a HPLC is recorded continuously as function of time most commonly with the help of a potentiometric recorder. Invariably, a recorder of 1 to 10 mV full-scale deflec- 

It is pertinent to mention here that before commencing the operation of a recorder, its zero point must be adjusted with the input zero, otherwise the baseline will also shift with slight changes in the attenuation of the signal. 

Besides, it is also equally important to adjust properly the amplifier gain so as to eliminate completely the dead-band and the oscillations. A recorder having inadequate shielding from the AC circuits may display 

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In addition, most devices provide operator control of settings for temperature and/or response slope, isopotential point, zero or standardization, and function (pH, mV, or monovalent—bivalent cation—anion). Microprocessors are incorporated in advanced-design meters to faciHtate caHbration, calculation of measurement parameters, and automatic temperature compensation. Furthermore, pH meters are provided with output connectors for continuous readout via a strip-chart recorder and often with binary-coded decimal output for computer interconnections or connection to a printer. Although the accuracy of the measurement is not increased by the use of a recorder, the readabiHty of the displayed pH (on analogue models) can be expanded, and recording provides a permanent record and also information on response and equiHbrium times during measurement (5). 

There are many industrial applications in which permanent records (extending over long periods of time) of the instrument readings are required. Chart recorders of various forms are available for this purpose. The most common general-purpose unit is the digital strip chart recorder, in which the input signal is used to drive the movement of a recording arm that passes over a paper chart in the y-direction. At the same time, the chart is... 

An interesting description of a commercial tin-plate installation appears in a special issue of the Norelco Reporter Each side of the coated steel strip can be traversed continuously by a separate measuring head, and the results appear on a two-pen strip-chart recorder located near the 4 x 2 x 9-foot dual electronic rack that energizes and regulates the two measuring heads some 100 feet away. 

The mixture is identical in each example. The peaks are shown separated by 2, 3, 4, 5 and 6 (a) and it is clear that a separation of 6a would appear to be ideal for accurate quantitative results. Such a resolution, however, will often require very high efficiencies which will be accompanied by very long analysis times. Furthermore, a separation of 6o is not necessary for accurate quantitative analysis. Even with manual measurements made directly on the chromatogram from a strip chart recorder, accurate quantitative results can be obtained with a separation of only 4a. That is to say that duplicate measurements of peak area or peak height should not differ by more than 2%. (A separation of 4a means that the distance between the maxima of the two peaks is equal to twice the peak widths). If the chromatographic data is acquired and processed by a computer, then with modem software, a separation of 4a is quite adequate. 

Conventional UV/VIS spectrophotometer (manual measurements from strip-chart recorder traces and calculations on the basis of fitted polynomials the extraction/separation step remains). 

In one laboratory, an atomic absorbtion instrument was placed on top of a three-foot knee-hole. Drainage from the instrument s atomizer went into a bottle underneath. Data from this instrument was recorded on a strip chart recorder placed on a typewriter stand. When in use, the recorder was at the operator s right, where it was easy to observe and adjust. WTien not in use, it was kept out of the way in the knee-hole, along with the operator s stool. 

Equipment instructions must be properly and promptly filed. A separate file should be set up for each piece of equipment and should include the smallest note packed with it. A lack of such files is an invitation to future problems. In one instance, a strip chart recorder that had not been used for several years seemed just right for a procedure but needed some minor repairs and parts. After a couple of hours of diligent search, the instruction book was finally found tucked away in a drawer. It could easily have been missed. In other less fortunate cases, it took time-consuming correspondence with the manufacturers to produce information that should have been immediately available in the file cabinet. 

The core - flood apparatus is illustrated in Figure 1. The system consists of two positive displacement pumps with their respective metering controls which are connected through 1/8 inch stainless steel tubing to a cross joint and subsequently to the inlet end of a coreholder 35 cm. long and 4 cm. in diameter. Online filters of 7 im size were used to filter the polymer and brine solutions. A bypass line was used to inject a slug of surfactant solution. Two Validyne pressure transducers with appropriate capacity diaphragms are connected to the system. One of these measured differential pressure between the two pressure taps located about one centimeter from either end of the coreholder, and the other recorded the total pressure drop across the core and was directly connected to the inlet line. A two - channel linear strip chart recorder provided a continuous trace of the pressures. An automatic fraction collector was used to collect the effluent fluids. 

In our system the data collection process is essentially a passive slave to the chromatograph, which is controlled by its own internal microprocessor. An amplifier matches the voltage output from the strip chart recorder terminals on the chromatograph to the A/D converter input. The data collection program uses the "Equilibration Pulse" and "Injection Pulse" relay closures shown in Figure 1 to synchronize the data collection process with the operation of the autosampler on the chromatograph. 

The experimental set-up for cellular oxygen measurements (p02) consists of following components p02 measuring micro chamber (volume 0.6 microliter), polarographic microelectrode, water-bath for constant temperature, chemical microsensor connected to a strip-chart recorder and gas calibration unit. 

A simple system is comprised of an isocratic pump, a manual injector, a UV detector, and a strip-chart recorder. A schematic diagram of an HPLC instrument is shown in Fig. 15.4. This simple configuration is rarely used in most modern laboratories. A typical HPLC system is likely to consist of a multi-solvent pump, an autosampler, an on-line degasser, a column oven, and a UV/Vis or photodiode array detector all connected to and controlled by a data-handling workstation. Examples of modular and integrated systems are shown in Fig. 15.5. Some of the important instrumental requirements are summarized in Table 15.2. 

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