Highly Accurate Square-Law Recorder
Abstract
The square-law recorder is an instrument designed to take signals from zero to one volt rms in a narrow frequency band centered at 50 kcas in input and record in strip-chart form the square of this input timessome fixed constant. The squaring process is performed by keeping the power to the filament of a temperature-limited thermionic diode constant by reducing the direct current to the filament as an ac signal is applied. Since the maximum power supplied by the ac signal is only a small fraction of the total filament power, the decrease in direct current is proportional to the square of the alternating current. The system has negligible zero drift, and the power scale is inherently linear without the use of large correction factors. The accuracy of the chart readings is better than one percent for values above ten percent full-scale deflection, and the zero drift is less than one-half percent full scale over a six-hour period.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 17, 1961
- Accession Number
- AD1226429
Entities
People
- J. A. Alexander
Organizations
- United States Naval Research Laboratory