An Improved Measuring Circuit For The Susceptance Variation Method

Measuring dielectric samples at frequencies up to 100 Mc by the susceptance variation method were described in the Experimenter about a year ago.* With the special holder used at that time, the two resonance voltage readings were taken at the same setting of the standard condenser, thus eliminating the corrections that are necessary for the change in conductance of the standard condenser when the resonance readings occur at two different settings. The capacitance measurement, however, was made...

Miscellany

THE MOTION-ARRESTING PROPERTIES of the Stroboscope are the theme of Quicker'n a Wink, Pete Smith's latest Metro-Goldwyn-Mayer Specialty. Produced through the cooperation of Dr. Harold E. Edgerton of the Massachusetts Institute of Technology, consultant on General Radio Stroboscopes, this film features the Strobotac, the Strobolux, and the continuous-film high-speed camera Type 651-A . ENGINEERS whose work involves the measurement and analysis of noise will be interested in a recent publication...

And The Strobolux

FOR THE PAST SEVERAL YEARS the effectiveness of single-flash photographs in stopping a multitude of types of motion has been vividly demonstrated in the popular press.1 Suspended action photographs of dancers, runners, tennis players, golfers and other athletes have been taken by means of the powerful single-flash equipment designed by Messrs. Edgerton, Germeshausen, and Grier of the Massachusetts Institute of Technology,2 under whose license General Radio Company manufactures the Strobotac...

P N

The resistance range as a whole can be raised by increasing B or TV. The upper limit alone can be raised by decreasing A. Of these three methods only the first and last are possible. A standard resistance of 1000 megohms is relatively unstable and inaccurate, and in any case is too near in value to the input resistance of the detector tube to be safe. The choice between increasing B or decreasing A depends both on convenience and on the range desired. Resistor B can be increased to 1 megohm...

Variacs In Combination

Connections for Variacs have been brought to our attention by users. Both of these use the Type 80-A Variac Transformer in combination with Type 100 or Type 200 Yariacs. The first of these, used by Mr. Louis A. Paine, Chief Engineer of Therm Electric Meters Co., Inc., uses the Variac as a potential phase shifter for Figure 1 below . Arrangement of Type 100 Variac and Type 80 Variac Transformer for varying the potential phase in testing wattmeters. Figure 3 below . By using two Variacs, the...

The General Radio Company

General Radio Sound Level Meter 759a

IN THE TWENTY-FIVE YEARS since its founding, the General Radio Company's products and markets have grown considerably beyond the limits implied by its name. Established in 1915 to supply laboratory measuring equipment to the infant radio industry, the Company now makes electrical instruments for varied applications, such as measuring the performance of broadcasting stations, the sensitivity of radio receivers, the noise generated by machinery, the speed of yarn spindles, and the vibration of...

Experimenter

The open-delta connection uses one less Variac than the wye. This diagram shows two Type 50-B Variacs in an open delta. Figure 4. The open-delta connection uses one less Variac than the wye. This diagram shows two Type 50-B Variacs in an open delta. Figure 5. Right Connections for current-equalizing choke when Variacs are in parallel. Figure 5. Right Connections for current-equalizing choke when Variacs are in parallel. Open-circuit voltage regulation is poor for this connection. fFor...

New Dial Plate

180 Degree Dial Plates

THE NEW Type 318-C Dial Plate, shown here, is intended for use with air condensers, variometers, and other variable circuit elements having a 180-degree angle of rotation. The scale progresses in a counterclockwise direction and has ten main divisions, each of which is divided into five small divisions. The scale is photo-etched with raised nickel-silver graduations on a flat black background. The diameter of the plate is three inches. It can be used with a l g- inch knob, either skirted or...

Using The Variac With Auxiliary Transformers

AMONG THE MANY AND VARIED LABORATORY USES of the Variac there are the occasional ones where currents or voltages exceeding the Variac rating must be obtained. When high currents are to be obtained at low voltages, or high voltages with low currents, an auxiliary transformer can be used, as indicated in Figure 1. An arrangement similar to that of Figure 1 a is available commercially as the Type 90-B Variac. The 230-volt models of the Variac have a center tap, 6,f which is not furnished on the...

Directreading Wavemeter For Ultrahigh Frequencies

758 Wavemeter Manual

Measuring the frequency of an ultra-high-frequency oscillator with the Type 758-A Wavemeter. THE TYPE 7 5 8- A WAVEMETER is a convenient instrument for measuring liigli frequencies in the laboratory, where quite frequently ease of operation is found to be more important than high accuracy. The direct-reading dial covers in a single rotation frequencies from 55 to 400 megacycles. This wide range of frequencies, which is covered without switching or changing coils, is particularly...

General Radio

__ As pointed out in a previous article, the maximum amount of power which can be handled by an assembly of Vari-acs in a three-phase system is Imax maximum allowable output current. This holds regardless of the type of circuit used, i.e., whether the Variacs are connected in a wye, a closed delta, or an open delta. This power can be handled in the vicinity of line voltage. When the over-voltage feature is used, rated current instead of maximum current must be used in calculating the output...

Guard Circuit For Capacitance Bridge Measurements

CIRCUIT is to provide a point to which the third terminal of a three-terminal im-pedance can be connected, so that the direct impedance between the other two terminals can be measured correctly bv means of a suitable bridge circuit. A typical combination of capacitance bridge, guard circuit, and three-terminal capacitance is shown in Figure 2. The direct capacitance C is measured by the bridge because the terminal capacitances are carried to the guard circuit, C providing coupling to the guard...

Broadcast Frequency Monitor For The Cycle Rule

The Federal Communications Commission, on and after January 1, 1940, the frequency of each new broadcast station, and of each existing station where a new transmitter is installed, must be maintained within 20 cycles of the assigned frequency. After January 1 1942, the frequencies of all standard broadcast stalions must be held to this tolerance. The FCC specifications for frequency monitors have necessarily changed as a result of the new tolerance specifications and, to meet these new...