EQUIPMENT AT MOUNTAIN LAKES 



127 



Figure (35. W10093 capacitance and conductance bridge 

 for use at high frequencies. 



resolution in balancing under severe conditions of 

 wave distortion. The set consists of an amplifier with 

 calibrated gain controls, an oscillator and modulator 

 circuit operating in conjunction with a 20-c band-pass 

 crystal filter, an output meter, and a regulated d-c 

 supply circuit operated on 1 15-volt, 60-c power. The 

 set has been designed to operate through the fre- 

 quency range 1 to 150 kc with switches to permit its 

 use as a wide-band or a sharply tuned instrument. 

 Continuous tuning control from 10 to 150 kc is ef- 

 fected by the frequency adjustment of the local 

 oscillator. 112 



Portable Signal Generators 



The Western Electric Company 17B Oscillator is a 

 heterodyne type operating on 60-c power and deliver- 

 ing levels up to 160 db vs 10" lu watt into a 135- or 

 600-ohm load and over a frequency range of 1 to 150 

 kc. Below 1 kc the power output decreases and the 

 wave form becomes poor. It is used extensively in im- 

 pedance measurements because of its highly stable 

 and uniform output level, accurate frequency calibra- 

 tion, and low harmonic distortion. 



The Hewlett Packard Oscillator, Model 200-Cr 

 covers a frequency range of 20 c to 200 kc. It is de- 

 signed to deliver a signal level of 150 db vs 10 -16 watt 

 into a 1 ,000-ohm resistive load, although its output is 

 not critically affected by the loading. The total har- 

 monic distortion, under proper operation, is less than 

 1 per cent. 



The Measurements Corporation Square Wave Gen- 

 erator, Model 71 , permits rapid determination of the 

 phase and frequency characteristics of many types of 

 amplifiers and networks when used in conjunction 

 with a cathode-ray oscilloscope. The time of rise on 

 the wave is about 0.2 microsecond with frequencies 

 from 5 to 100,000 c. The Fourier analysis of these 

 waves shows components that give a resultant range 

 of investigation from 1 c to several megacycles. 



The Dutnont Electronic Switch and Square Wave 

 Generator, Type 135 A, produces square waves at 10 

 to 500 c with a form that reaches full amplitude with- 

 in a few microseconds. In addition to its usefulness in 

 studying the performance of amplifiers and other net- 

 works, it may be used in con June lion with a cathode- 

 ray oscilloscope to make comparison studies of ampli- 

 tude, wave form, phase, and frequency between two 

 electric signals. 



Cathode-Ray Oscilloscopes 



Practically all measuring circuits require cathode- 

 ray oscilloscopes. Dutnont Type 175 A is used to pro- 

 vide visual monitoring in each of the 15-c to 150-kc 

 test systems. A Dutnont Type 217 is used with an 

 auxiliary circuit supplying higher accelerating poten- 

 tials for special studies of transients requiring high- 

 speed oscillograms. 



A Renter Model 5 5o operates at frequencies up to 

 1 mc and is useful for observing wave forms at the 

 higher frequencies and for observing carrier modu- 

 lator balance. 



Wattmeters 



A thermocouple wattmeter and a recording-type 

 wattmeter have been developed by the laboratories 

 for the measurement of power over the large fre- 

 quency range used in underwater acoustics. The two 

 operate on different principles and the second was 

 particularly designed to be used in conjunction with 

 the present electrical systems. 



Thermocouple Wattmeter?*'™ As the circuit of the 

 thermocouple wattmeter shows in Figure 66, the in- 

 strument can measure current and voltage as well as 

 power. The measurement of these three quantities 

 allows a calculation of the load impedance. Other 

 features of the design are that the power range switch 

 tends to keep the impedance range of the instrument 

 constant and that the power measurement is inde- 

 pendent of wave form. 



This meter is designed to operate for load impe- 



