New PAR Lock-In Amplifier Measures Signals in the Presence of Noise by Crosscorrelation
T r a n s i s t o r i z e d L o c k - i n A m p l i f i e r — Model H R - 8
The P A R Model H R - 8 Lock-In Technical Features: Amplifier represents a significant ad Frequency Range: 1.5 cps to 150 KC vance in signal processing equipment continuously tunable in 5 ranges. ^ " Time Constants: 11 values in 1-3 se CJL for experimentalists who must meas quence extending from 0.001 to 100 10M ure low-level signal intensities in the seconds. Single or double section RC ~—— l d b presence of noise. It employs the the filtering. 1M oretically optimum technique for sig Pre-Amplifiers: Interchangeable low~~~- 0.5db noise pre-amplifiers, operable either nal recovery, and can be incorporated within the HR-8 or remotely, are used. f 0.5db rz^ 100K into a large class of experiments in Type A: Differential 10 megohm input. ^ Type Β : Low impedance transformer which the signal of interest is, or can 1 • ldb input for low source impedances. be made periodic, and in which a ref Sensitivity: 21 c a l i b r a t e d f u l l scale 3db erence voltage related in frequency ranges in 1-2-5 sequence. and phase to the signal can be ob With Type A Pre-Amplifier: 100 nanovolts to 500 millivolts rms. tained. The Model HR-8 first ampli lOdb v ^d With Type Β Pre-Amplifier: 1 nanovolt fies and bandlimits the input signal ^3s^! f to 5 millivolts rms. FREQUENCY CPS *• and then crosscorrelates it with the Output: ± 10 volts full scale, singlereference signal, suitably phase shifted ended with respect to ground. Will Contours of constant noise figure for a and shaped. The crosscorrelation of d r i v e g a l v a n o m e t r i c a n d servo typical PAR Type A preamplifier plotted to show dependence on frequency and input and reference signals yields a recorders. source resistance at 300° K. Amplifier Frequency Selective Amplifiers: Notch DC output voltage proportional to the network in negative feedback loop used operated single-ended. signal of interest, while the cross- in both signal and reference channel correlation of the reference and noise tuned amplifiers. Reference channel Write for bulletin No. 120 on the results in no net DC voltage. The sys Q of 10. Signal channel Q adjustable HR-8 or ask for information on PAR's Amplifiers tem can also be described as a con from 5 to 25 with calibrated dial (no complete line of Lock-In gain change with Q adjustment). and accessories. tinuously integrating, highly sensitive, Phase Adjustment: Calibrated 360° phase conscious voltmeter, the re phase shifter, providing continuous ro PRINCETON sponse of which is "locked" to that tation as well as a four position quad APPLIED RESEARCH CORP. rant switch which shifts phase in 90° particular frequency and phase at increments. Dept. N which the signal information has been Price: $2,250 with either Type A Or Box 565, Princeton, Ν. J., Tel. (609) 924-6835 made to appear. Type Β Pre-Amplifier. db
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Circle N o . 87 on Readers' Service Card 16 A
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ANALYTICAL CHEMISTRY
