Photocell recording

The reflectivity within the halo is not constant one observes a maximum close to the radioactive source with a decrease outwards. The tracing of reflectivity curves with a photocell, recorder, and moving stage has shown that the decrease curves are smooth but sometimes stepwise (Figure la, b). The width of the halos is difficult to estimate by a subjective method, and our instrumental measurements are still too few to allow, definite interpretation. However, the width generally varies between 20 and 50 microns. Preliminary observations suggest that the intensity of the halos is proportional to the quantity of uranium (Figure 4c). 

One of the first precise vacuum or inert-atmosphere instruments was designed and constructed by Whitehead and Breger (37). The furnace was constructed from an alundum core, 9 in. in length by 2 in. ID, wound with Chromel A resistance wire. The core was shielded by four sheet-nickel cylinders, mounted on three posts, and the entire assembly was placed inside a 12 x 24-in. Pyrex bell jar. All electrical connections were made through the bottom of the bell jar mounting base. The sample block was made in the dimensions shown from Type 446 or 309 stainless steel. The furnace heating rate was controlled by a Leeds and Northrup Micromax controller the differential temperatures were recorded on a Beckman Photocell recorder. 

Titrocolormat is the name we have given to the basic titration instrument which consists of a metal cabinet housing electrical components and supporting optical components, a magnetic stirrer, and a titration vessel. A support rod is provided for burets and refill vessels. Electrical outlets in the rear of the cabinet provide for connection to power, lamp, buret, stirrer, photocell, recorder, and printer. The titration vessels are held on top of a magnetic stirrer which is raised and lowered by a lever control, placing the vessels into or out of the optical beam. 

Mettler softening point method — ASTM D 3461-76. This is the most recent method. This automatic method measures the temperature at which the resin flows out of a sample cup under its own weight. The temperature is recorded when the first drop crosses the light path of a photocell (Fig. 21). This method is quite accurate and reproducible. 

The glass reaction vessel is equipped with a light source, photocell, and 550-nm filter to detect the indicator color change (red to pale yellow). The signal from the photocell is continuously monitored using a strip recorder. Quantification is obtained by comparison of the time required for ozonolysis of the sample compared to that required for a pure compound with known saturation. 

Each cage contained six infrared photocell beams arranged around the base of a circular tract. Each interruption of a beam registered a count on a total-event counter and on a cumulative recorder. Cumulative IV doses at 30-minute intervals were administered over dose ranges that included the complete spectrum of effects on SLA. 

Quandt (1962) measured the values of (CfICm - 1) at various axial positions of an air-water mixture flow in a 0.25-in. X 3-in. channel and converted the raw data to the exchange mass flux, pLV(, as shown in Figure 5-23. He also measured the film velocity Vf by injecting a pulse of dye into the liquid film and recording its transport time between two photocells. Such measured data are shown in Figure 5.24. By using the measured values for Vf, the liquid film thickness t may be calculated as... 

Chopper is a rotating wheel whose function is to break the steady stream of light from the hollow-cathode-lamp into an intermittent light that gives rise to a Pulsating current into the photocell this current is duly amplified and recorded. 

Light from the source(s) is focused into the cell, that consists of sample and reference sample and the two chambers are separated by a diagonal sheet of glass. After passing through the cell, the light is diverted by a beam-splitter (B) to two photocells (Pj and P2 respectively. A change in the observed refractive index (RI) of the sample stream causes a difference in their relative output, which is adequately amplified and recorded duly. 

Figure 13. Optical scanning cross-sectional area recorder. Cylindrical sample shadow is magnified and monitored during extension hy a bank of linearized photocells (83)...

For recording of the emission spectrum, the emitted radiation is focussed on the slit of a monochromator and intensities measured attach wavelength. Since sensitivities of photocells or photomultipliers are wavelength dependent, a standardization of the detector-monochromator combination is necessary for obtaining true emission spectrum This can be done by using a standard lamp of known colour temperature whose emission characteristics is obtained from Planck s radiation law. The correction term is applied to the instrumental readings at each wavelength. Very often substances whose emission spectra have been accurately determined in the units of relative quanta per unit wavenumber intervals are... 

Automated Hydrometers. One form of hydrometer utilizes an opaque stem which, as the stem rises and falls, effects the amount of light which passes through a slit to a photocell. In this way. the photocell output is proportional to specific gravity and may be recorded by an electric instrument. In another industrial version, designed for remote transmission, the hydrometer is contained within a metal cylinder. A rod connects the bottom portion of the float to an armature, which moves vertically between inductance coils. Changesin inductance are transmitted by cable to a central instrument panel receiving instrument. 

Figure 6.1. Schematic drawing of the holeboard apparatus used to record behaviour of rats. The box is 70 70 cm and has 32 holes in the floor (circles). The position of photobeams recording nonspecific behavioural activity (variable x,) are indicated by black triangles. These photobeams also record the two locomotion variables (x2 and x3) indicated by arrows. The frequency and accumulated duration of hole visits, comer visits and raising on the hind-legs (variables x4-x9) are recorded by separate photocells [2J. The 10th variable is the ratio between the activity during the second and the first half...

It has proven feasible to take the electrical output from photocells or phototubes and either with or without amplification record the magnitude and duration of the output. The recording may be made either in the form of a line tracing on a moving chart or may be converted to numerical values and printed by a read-out device. Further refinements can be supplied in which the instrument converts optical densities (or transmittance units) to concentration values. More intricate recording colorimeters or spectrophotometers are also available for continuous scanning and recording of complete spectra from ultraviolet to infrared. No further discussion of these will be attempted since they do not serve a normal function in routine clinical chemistry laboratories. 

Recording Colorimeter. The flowing stream which now has attained its appropriate color development is passed into a recording colorimeter. The air is removed in a small precell attachment feeding the flow cell. The colorimeter employs the dual beam principle and compares the electrical output of the photocell from the reference side with that from the flow cell. This difference is then traced as per cent transmittance on a conventional chart recorder. The solution which has been read and... 

Apparatus. Contact angle measurements were made on a Model A-100 Rame-Hart version of the NRL Contact Angle Goniometer. Exposures were carried out in a forced-draft hood with the unfiltered radiation from a General Electric UA-3 medium-pressure mercury lamp. Spectra were recorded on a Perkin-Elmer Model 350 ultraviolet spectrophotometer, a Beckman IR-12 infrared spectrophotometer with a Wilks Model 7 internal reflectance attachment, and an Aminco-Bowman Spec-trofluorometer with a 1P28 photocell. 

Figure 10. Schematics of the experimental setup for intracavity laser absorption spectroscopy (ICLAS). CD chopper driver PM power meter Mj, M2, M3, M4 spherical high reflection mirrors Mp = pump mirror MN monochromator PMT photomultiplier SP silicon photocell PC Pockels cell WF wedged filter LIA lock-in amplifier R recorder MS microscope OF optical fiber S sample (solution on BLM) IEM instruments for electrical measurements (see Figure 2).

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