Photoelectric Counter Research Articles

An Electronic Coleoptile Measuring Device

An apparatus for the rapid measurement of large populations of cereal coleoptiles is described. It has application in seedling evaluation and the study of factors affecting early seedling growth. The seedlings are grown in shallow trays and passed through a photoelectric counter which records the number of coleoptiles present at successive 1 cm intervals of height above the substrate. A frequency distribution for seedling height is obtained from the difference between counts at consecutive levels, and the mean height from the total at all levels. The estimate of mean height is typically accurate to within about 1 mm for batches of 200 seedlings. The measurements are non-destructive and may be repeated at intervals to obtain a growth curve.

Balloonborne Measurements of Condensation Nuclei

Abstract A condensation nuclei (CN) counter has been developed for balloonborne use at ambient pressures in the troposphere and stratosphere. The instrument employs a thermal gradient diffusion cloud chamber to produce particle growth and a photoelectric particle counter for detection. After extensive laboratory tests, the instrument was successfully flown on several balloon soundings over Laramie. The results show a roughly constant mixing ratio in the stratosphere with a CN concentration of about 20 cm−3 at 15 km. The vertical profile of CN in the troposphere displayed concentration fluctuations ranging between 200 and 2000 cm−3 with a definite maximum in the mixing ratio just below the tropopause.

A photoelectric counter for tick larvae and small insects.

A description of the design, construction, and use of a photoelectric counter suitable for counting tick larvae or small insects is given. To facilitate construction of the apparatus, commercially available components were used as much as possible. Standard errors of replicate counts of tick larvae were 0.3% for small samples and 0.45% for larger samples.

Calibration of a photoelectric aerosol jet counter of the AZ type

Calibration of a photoelectric aerosol jet counter of the AZ type

A Portable Aerosol Detector of High Sensitivity

A portable photoelectric nucleus counter, with similar sensitivity to the Pollak photoelectric nucleus counter with convergent light beam, has been developed and calibrated. This instrument has been incorporated into a packaged measurement system which allows the experimenter to determine the effective diffusion coefficient and fraction charged, of the natural aerosol, in uncontaminated areas. The photoelectric counter has comparable accuracy to the absolute (Aitken, Scholz) counters in the concentration range of interest, and is capable of determining the concentration once per minute.Field tests of the prototype instrument were conducted near sea level in Greenland. The concentration of natural aerosol in this area ranged from 150 to 200 particles cm−3. The instrumentation had sufficient sensitivity to detect a gradual increase in particle size at this low concentration.

Measurements of Aitken nuclei, cloud nuclei, and ice nuclei in precipitation at the Jungfraujoch, Switzerland

Aitken nucleus concentration measurements with a photo-electric counter at the Jungfraujoch show a maximum at almost neutral stability of the air in the layer up to ≈3500 m.

The calibration curve of photoelectric counters and computation of particle size distribution when the relationship between particle size and electrical pulse amplitude is ambiguous

Calibration curves are presented of a photoelectric aerosol particle counter using forward scattered light in the range 2·2–18·2°. A range of ambiguity in the relationship between pulse amplitude and particle size can be seen in these curves and a method is proposed for the calculation of particle size distribution within this range.

A flame sensor for high-temperature ambients

The flame sensor consists of a photoelectric counter tube which is triggered by ultraviolet photons emitted by flames in the spectral region beyond the solar cutoff. Tubes of this type have been made previously, but this new tube differs in being able to operate in ambient temperatures up to and in excess of 1000°F. The new tube has high sensitivity and a lower operating voltage than older tubes. The flame sensor is encapsulated in a titanium and forsterite ceramic envelope and uses a sapphire window to admit the ultraviolet photons. The photocathode consists of a molybdenum rod which has been cleaned by heating and sputtering. The anode is a molybdenum hemisphere, which also serves as a mirror to concentrate the light from the flame on the photocathode. The gas-fill is 100 torr of a helium-argon mixture, where the small amount of argon is used to help remove helium metastables following a count. The sensor operating voltage is about 150 V, and a dead time of 1 ms or more is used to avoid multiple counting. Typical counting rates obtained with a small methane flame at 12 ft are 60 per second. A sensor was life-tested at 1000°F in air for longer than 2000 hours.

Photoelectrical Counting of Outgoing and Incoming Honey Bees123

A photoelectric counter was developed for single-frame observation beehives. Glass tubes protruding in opposite directions from the center partition separated the outgoing from the incoming honey bees, Apis mellifera L. Each bee that passed through the counter in each direction was recorded on a digital counter. A single time lapse camera periodically recorded the data from both counters.

Absolute calibration of a photoelectric condensation nucleus counter at low values of nucleus concentration

A new absolute condensation nucleus counter was constructed to investigate the accuracy of the calibration widely used with the Pollak-Nolan photoelectric condensation nucleus counter. An attempt was made to standardize the conditions affecting calibration and, using the new counter, to recalibrate the photoelectric counter at values of extinction less than 16%.

An automatic recording cell counter for monitoring growing populations of unicellular micro-organisms

Modifications and readily assembled accessories are described for converting the manually operated photoelectric Fisher Autocytometer blood cell counter into a versatile automatic sampling and recording monitor for following growth curves in axenic unicell populations. Three versions of this equipment have been developed, between them covering a wide range of cell densities extending from a few dozen to 500 000 cells per ml. A batch sampling system is used for handling very low cell densities, continuous sampling with autodilution is used for high cell densities, and a recently developed model, in which the sample is pumped continuously through a sterile counting loop and returned to the parent culture, is suitable for use with very small culture cuvettes.

A Photoelectric Counter to Monitor Olfactory Response of Moths12

A Photoelectric Counter to Monitor Olfactory Response of Moths12

The Design, Operation, and Testing of a Photoelectric Fish Egg Counter

The Design, Operation, and Testing of a Photoelectric Fish Egg Counter

An Accurate Photoelectric Egg Counter Using a Jet Pump

An Accurate Photoelectric Egg Counter Using a Jet Pump

New calibration of photo-electric nucleus counters

A new calibration of the improved version of a photo-electric nucleus counter with a fog-tube of 3.85 cm air-column diameter and blotting-paper lining and of a photo-electric counter Model 1957 with air-column diameter of 2.5 cm and ceramic lining was carried out by adjusting the calibration curve of 1946 with reference to the considerably improved absolute (Aitken type) counter with stereophotomicrographic recording.

A photoelectric particle counter for use in the sieve range

A photoelectric particle counter for use in the sieve range

Photo-electric condensation nucleus counters of high precision for measuring low and very low concentrations of nuclei

A description is given of photo-electric condensation nucleus counters of high precision for measuring low and very low concentrations of nuclei such as are experienced in aeroplane ascents and occur in maritime, arctic and antarctic aerosols, and also in laboratory investigations as e.g. with the resolution of polydisperse aerosols into their components using the dynamic method. One, for low concentrations, employs the increase of the length of the light path through the fog using two identical photo-electric nucleus counters of high precision, Model 1957 in parallel, combining them optically into a twin-counter. In this model the direct light-beam of the previous constructions is replaced by one bent at right angles with the aid of a prism, thus permitting easy access to the photocell. Furthermore, it is equipped whith quick action toggle clips and fitted with a fog-tube of large internal diameter the air-column of which can be reduced to any desired smaller diameter by easily exchangeable ceramic linings of appropriate central bore. The second arrangement, for very low concentrations, uses only one photo-electric counter with the standard length (58.7 cm) of the light path but employs for measuring the extinction an electrical compensation method with two galvanometers of different sensitivity which opens the scale of the first galvanometer by a factor determined by the ratio of the sensitivities of the two galvanometers. Measurements of concentrations of less than 220 nuclei per cm3 during their decay in a large balloon gasometer with the new set-up are given which demonstrate the accuracy and advantages of the photo-electric nucleus counter for measuring very low concentrations.

On the fog formation in the photo-electric counter

The operation of a photo-electric nucleus counter has been examined in detail to investigate the causes of uncertainties in the readings with a photographically recording galvanometer. Various peculiarities are pointed out and it is suggested that these are the result of deposition of fog droplets on the glass closing plates and limit the accuracy of a counter to about 5%. Unsuccessful attempts to eliminate this deposition are given and the possibility of solution is offered by reverting to a different form of fog chamber.

Some airborne observations of condensation nucleus concentration

The measurement of condensation nucleus concentration from an aircraft is considered and preliminary observations made with a photo-electric condensation nucleus counter discussed. It is concluded that at heights up to 6000 ft concentrations of condensation nuclei vary, from 200 cm−3 in clean maritime air to 5 × 103 cm−3 generally over large industrial areas and 35 × 103 cm−3 downwind of specific industrial sources. It appears that sea spray makes a contribution to the nucleus population.

The relation between the concentration of atmospheric condensation nuclei and other meteorological elements at valentia observatory

Measurements of the concentration of condensation nuclei made twice daily (0h and 12h GMT) with aNolan-Pollak photo-electric counter at Valentia Observatory, in the extreme Southwest of Ireland, over the 4 years 1951–1954, are analysed to show relation with other meteorological elements. It is found that concentration at 12h is generally higher than at (h and that precipitation at the time of observation or in the preceding hour reduces concentration by between 40% and 50%. From measurements made when there was no precipitation at the time or in the previous hour it is found that concentration decreases with increasing wind speed but does not vary appreciably with wind direction apart from a sector from which pollution could be expected. High concentrations are found with visibility below 7 miles, with inversion of temperature, when free from the effects of pollution, follows fairly closely that of duration of bright sunshine.