Page 505 - Instrumentation Reference Book 3E

488 Electrical measurements
- I -
fi + Kfosc
Input signal fi - Kfosc fi - Kf osc
I
fi Amplified Schmitt Counter
Mixer t- nc counts
low-pass
filter trigger in gate period
Main gate
lf
Kfosc - t
Signal - -
Switched detection r\ --
filter - and Processor
filter control K
-

Gate time
Multiplier
generator

Cryitat oscillator
frequency fosc
(a) fi= CtK f
(:, ) OSC
- - - - - - - -- - - - -
fi I --1 Phase-locked
.-t Sampler - Video I vol tage-con t rol led
amplifier 1

Input signal

I 2
Conventional I Display ----c
counter I fi Counter
L-----L -----__ c
vstal
Main gate oscillator
frequency foSc
(b)
Figure 20.80 (a) Heterodyne converter counter; (b) transfer oscillator counter (from Hewlett-Packard 1977a).