SECONDARY FREQUENCY STANDARD

"From HP Catalog 18A" Laboratory Instruments", Copyrighted 1945."

 

ADVANTAGES:
Supplies standard frequencies, 100 cps, 1 kc, 10 kc, and 100 kc
Frequencies available simultaneously
Stable operation
Sinusoidal wave shape
Separate terminals for each frequency
Low output impedance

USE IT FOR:
Calibrating audio oscillators
Calibrating supersonic oscillators
A time standard
Checking oscillator stability

The Model 100B Secondary Frequency Standard provides an extremely useful and convenient source of standard frequencies of 100 cps, 1 kc, 10 kc, and 100 kc. It is an accurate laboratory standard for calibration and comparison purposes.
The circuit of the Model 100B consists of a 100 kc crystal controlled oscillator and  three frequency divider circuits which divide in a ratio of 10 to 1. The fundamental divider circuit consists of a modulator divider tube with a resonant circuit tuned to f/10 and a modulator multiplier tube with a resonant circuit of 9f/10.

The operation of the circuit can be explained by assuming a small voltage in the resonant circuit of the modulator divider tube. This voltage is applied to the grid of the modulator multiplier tube, and the input control voltage is also applied to this tube. The two voltages mix to supply an output frequency of 9f/10, which is fed to the grid of the modulator tube where it is mixed with the input control frequency (f), and results in a frequency of f/10 in the modulator divider tuned circuit. The action is repeated and the voltage is built up until a stabilized condition is reached. Thus the output of the divider unit is controlled by the input frequency.
By cascading the 100 kc generated by the temperature-controlled oscillating quartz crystal down through three dividers, accurate fixed frequencies of 10 kc, 1 kc, and 100 cps are also made available. See figure 1.

 

USES

These frequencies are available through a selector switch (on front of panel) or individually from binding posts (rear of chassis). All four fixed frequencies can be utilized at separate test stations simultaneously, an economical feature.
The Model 100B provides four standard frequencies for accurate measurement purposes such as for calibrating oscillators, frequency meters and supplying test signals of high accuracy. The output wave shape is sinusoidal which will allow easy recognition of high fractional lissajous patterns such as 53/5 or 52/5. Thus exact measurements can be made of frequencies 1% or 2% apart in the audio spectrum, and up to 100 kc. With a distorting amplifier and a conventional mixer system harmonics may be obtained for frequency calibration to 20 megacycles or higher, even though the waveform of the standard is sinusoidal.

The output system is designed to isolate each frequency. The internal impedance of the output system is sufficiently low to permit the use of long lengths of low capacity shielded cable to distribute the standard frequencies in the laboratory or the test department.

 

 

SPECIFICATIONS

Two models are available. The 100B which has a temperature controlled oscillating quartz crystal, and the Model 100A which is similar to the 100B but does not have temperature control.

Accuracy: The Model 100A is provided with a 100 kc crystal having a temperature coefficient of 3 cps per megacycle per degree centigrade. The crystal oscillator is arranged so that the frequency can be adjusted over a range of approximately ±8 cps at 100 kc.
This feature allows the frequency to be set to a primary standard such as National Bureau of Standards Station WWV. The frequencies are correct within ±.01% over a room temperature variation of ± 33 degrees Centigrade. The Model 100B is provided with a temperature controlled crystal which maintains the frequency within ±.001% from minus 10 degrees Centigrade to plus 50 degrees Centigrade. It is also possible to adjust the frequency of the Model 100B approximately ±8 cps at 100 kc.

Output: An output voltage of at least 5 volts is provided on all frequencies. The internal impedance of the output system is approximately 200 ohms and satisfactory wave shape can be obtained with a load impedance as low as 1000 ohms.

Wave Shape: The output wave shape is sinusoidal to a degree that will allow easy recognition of high fractional Lissajous patterns such as 53/4 or 52/5. Thus, exact measurements can be made at frequencies 1% or 2% apart in the audio spectrum, and up to 100 kc. With a suitable distorting amplifier and mixing system harmonics may be obtained for frequency calibration to 20 megacycles or higher.

Power Supply: The Standard operates from 115 volts 50/60 cycle power supply, and the power supply is regulated to minimize line voltage fluctuation effect. Power drawn is approximately 105 watts.

Mounting: The Model 100 is available in either cabinet or relay rack mounting. The panel size is 19" x 10½", and the depth is 12".

Net weight, 53 pounds; shipping weight, 95 pounds.

Note: When ordering specify if temperature control of the crystal is desired; otherwise, specify ambient temperature at which crystal frequency should be set.
 

SUPPLEMENTARY FREQUENCY DIVIDER

The Model 110 Frequency Divider Panel is for use in conjunction with Models 100A or 100B to supply frequencies not ordinarily generated by these instruments. The Model 110 can be supplied to generate frequencies between 10 and 100 cycles per second, or between 100 and 1 million cycles per second. The Model 110 Frequency Divider Panel is supplied only on special order to meet particular requirements.
 

Pius Steiner, 24.Sep.12

Weitere Posts (1) zu diesem Thema.