Other meters in this series were DC Ammeters, milliammeters and microammeters in the same case and configuration. It was a 1% core magnet moving coil type of design with an accuracy within ½ of 1% in a bakelite case. The Weston Model 931 DC Voltmeter from 1956 ranged to 3 V DC at 10,000 ohms per volt. Limitations became a problem as higher speed films like 400 and 500 ASA were being introduced since this device could only be used up to Exposure Index (E.I.) settings of ASA 250. The design was made so that one could use the left or right hand to roll knobs on either side.
It was designed to be used with one hand, so the user would grip the bottom portion contoured on the sides and use the thumb to rotate the knob. Alternately, they could rotate the knob until a desired aperture is found and then read the resulting shutter speed. The amateur photographer could then read the proper aperture. It had a knob on its side that the user would turn to get a desired shutter speed. To get a faster speed, you would uncover more of the cell, which allowed for a higher reading. This calibrated the meter for the film speed used by the photographer. It used a revolving plate that partially covers a selenium cell on the back of the device so that the user would need to hold it upright at eye-level. Easy to use, just point and read the exposure. This Weston Direct Reading Exposure Meter, Model 854, from 1956 was a "direct reading" meter for the amateur photographer. In the UK, where it was made, it was sold with a leather case for £3, 7 shillings, and six pence. It measured 4 5/8" high by 2 5/8" wide with a depth of 1 7/16" and weighed in at 12 ounces. It read light values (foot candles) but there is no mechanism to convert them to exposure settings for cameras using shutter speeds, apertures, and file speeds. Since the voltage divider circuits are built from series resistances, a resistor inserted in series with the meter movement was used (using the movement's own internal resistance as the second resistance in the divider).Ī Weston Model E703 Lightometer was used for general light intensity and not photography. The design used to create such a circuit was a voltage divider used to proportion the total measured voltage into a lesser fraction across the meter movement's connection points. This will extend the meter movement's range to higher voltages. The potential drop across the galvanometer itself is small, and the value of the multiplier is adjusted to allow most of the potential drop to be measured to take place across it.Ī stand-alone meter movement was only able to measure around 0.5 V, so in order to measure larger voltages, a proportioning circuit allowing only a precise part of the measured voltage to drop across the meter movement must be created. The analog voltmeter back in the 50s had a galvanometer movement with a multiplier resistor (see above, I think a 60k ohm maximum resistance value) in series with it. This Model 455B transistor amplifier telephone repeater datasheet provided installation and maintenance information in addition to specs, and below you can see the schematic for the 453B transistor amplifier. Circa 1959, Altec Lansing developed the first solid-state telephone repeater amplifier shown above. Telephone repeaters made long distance phone service possible between 19. The Model 100 was the first commercial transistorized amplifier, and when co-founder Tom Brown visited customer MIT, he found that they were discarding the boxes to make them smaller. Other early products, in wooden boxes, included a Differential AC Amp, Square Wave generator, Variable Gain Preamp, and AC Millivolt Meter. The first product was the Model 100 AC Decade Amplifier. That year Burr-Brown started with “instruments” in wooden boxes. This slideshow features some items from the collection from around 1956, to give you an idea of what instruments looked like when EDN was born.īurr-Brown was incorporated on the same day EDN published its first issue, May 8, 1956. He is hoping that someone will appreciate what this collection represents and can offer help to preserve it. He has contacted many institutions including the Smithsonian in Washington, without success, for a variety of reasons. Skolnik has been looking for several years for a proper institution to maintain his collection that took 50 years to accumulate, refurbish, and document. Howard Skolnik, a former colleague and key analog mentor from my Burr-Brown days, has always had a passion for significant products made by pioneering electrical instrument companies and has accumulated a large collection over the years that includes Burr-Brown, General Radio, Leeds, and Northrup and Weston.
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