Substitution Method

For the measurement of capacitance below 1000 n j,f, excellent accuracy for dissipation factor as well as capacitance can be attained by the use of a substitution method in the standard arm. Although the procedure for this type of measurement is fairly obvious, it is outlined here because of its importance. An initial balance is made with a capacitance of about 1000 ifii in the P arm, with the unknown in place and connected to the standard on the grounded side. The high-potential connection...

Specifications For Type A Ultra H I G H Frequency Oscillator

Frequency Range 150 to 600 Mc (200 to 50 cm wavelength). Calibration The frequency determined from the chart converting dial reading to frequency is accurate to fc 2 2 with no load connected to the oscillator. Output Power 3 to 4 watts up to 400 Mc (75 cm) decreasing with frequency to about 1 watt at 600 Mc. Output Impedance Effectively of the order of 75 a slow-motion drive, which carries a dial calibrated in divisions representing approximately 0.01 cm change in wavelength, is used for...

In This Issue

Impedance Bridges Assembled from Laboratory Parts Part IV 4 More Information, THE ELECTROMECHANICAL OSCILLATOR, whose frequency is controlled by a tuning fork, has many uses in electrical communications. The Type 813 Oscillator and its predecessor the Type 213 have been used, for instance, as power sources for bridge measurements and for transmission measurements on lines and cables, as modulating sources for test oscillators and radio-beacon transmitters, and as test-tone sources for...

Use Of The Vibration Meter

In use the vibration meter has exceeded all expectations. The ease with which readings may be taken, the provision of the three characteristics namely, acceleration, velocity, and displacement and the extension of the range down to 2 cycles per second with substantially flat response characteristics provide a degree of flexibility hitherto unapproached in commercially available vibration-measuring apparatus. It has already been applied to a wide range of applications, in the manufacture and...

Info

Panel view of a Type 684-A Modulated Oscillator with Type 774-V Coaxial Adapter installed. The adapter fits one of the mounting holes for the standard binding post terminals supplied with the instrument. A metal button to cover the other hole is furnished. Figure 2. Panel view of a Type 684-A Modulated Oscillator with Type 774-V Coaxial Adapter installed. The adapter fits one of the mounting holes for the standard binding post terminals supplied with the instrument. A metal button to...

Dissipationfactor Balance

The capacitances across the ratio arms have an important effect on the dissipation-factor balance. To a first approximation the equation governing this component of the balance may be written as It is, of course, desired to compute Dp from the equation Dp Dn ItyajCat. To be able to do this with reasonable accuracy it is necessary to keep the difference Qa Qb small with respect to Dp. At this point it may be well to discuss the effect of small residual inductances in the ratio arms. Figure 5 is...

Mbm

OUR MANUFACTURING AND ENGINEERING FACILITIES are heavily overloaded at present with urgent work, most of it directly connected with the National defense program. Because of this, we are unable to accept most orders for equipment of special design. We are making every effort to maintain adequate stocks and to make prompt deliveries of standard apparatus, much of which is also necessary for the defense program, but owing to slow deliveries of raw materials and parts, as well as to our own...

The Resonance Bridge

The resonance bridge, shown in series form in Figure 2, is undoubtedly the most accurate method available for measuring coil resistance at audio fre-quencies. Since the reactance of the P arm is reduced to approximately zero, the resistance balance becomes the dominant one, and the circuit residuals have only a second -order effect on it, while having a comparatively large effect on the reactance balance. This method, then, although quite accurate for resistance measurements, is not very...

General Radio Company

30 STATE STREET - CAMBRIDGE A, MASSACHUSETTS BRANCH ENGINEERING OFFICES 90 WEST STREET, NEW YORK CITY 1000 NORTH SEWARD STREET, LOS ANGELES, CALIFORNIA at very high frequencies when the amplitude of vibration is sufficient. Sound, as generally encountered, is a vibration propagated through the air, but it is also transmitted through various other media and generally originates as an actual mechanical vibration in or of some solid structure. To trace noise to its source, therefore, through the...

References

Tuttle, Type 726-A Vacuum-Tube Voltmeter General Radio Experimenter, Vol. XI, No. 12, May, 1937. 2D. B. Sinclair, The Type 726-A Vacuum-Tube Voltmeter as a Radio-Frequency Ammeter General Radio Experimenter, Vol. XIII, Nos. 3 and 4, August-September, 1938. 3D. B. Sinclair, A Voltage Multiplier for Use With the Vacuum-Tube Voltmeter at Radio Frequencies General Radio Experimenter, Vol. XIV, No. 12, May, 1940. 4L. S. Nergaard, Electrical Measurements at Wave Lengths Less Than Two Meters...

Type B

AN INTERESTING APPLICATION of the Strobotac and Strobolux to advertising is shown in the accompanying photograph of the display used by getting display interest with the strobolux SKF Industries, Inc., at the Southern Textile Exhibit held last spring. The eight spindles, each bearing a letter, were driven at a constant speed by a chain drive. The two rows of tension pulleys we re driven similarly, but at a different speed from that of the spindles. Contactors on one spindle and one tension...

Capacitance Bridges

Figure 1 shows a generalized capacitance bridge circuit and the complete equations of balance. This circuit can represent any one of a number of well-known capacitance bridge circuits, depending upon the relative magnitudes of the various impedances shown. For example, if capacitances Ca and Cb are zero, we have the familiar series-resistance type of capacitance bridge, wherein the losses in the P arm are balanced by the resistance N in the standard arm. This circuit is used in the General...