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Usually use an op-amp circuit
Often found as a pre-amplifier to ADC circuitry
Simple circuit to computer natural logarithm Map binary values to analog outputs (voltages)
Most devices have a digital interface – use time to encode value
Time-varying digital signals – almost arbitrary resolution
pulse-code modulation (data = number or width of pulses)
pulse-width modulation (data = duty-cycle of pulses)
frequency modulation (data = rate at which pulses occur)
V VIN VOUT = loge ( VIN ) V
t 1 #$ %& $ ( Pulse a digital signal to get an average “analog” value
The longer the pulse width, the higher the voltage
Pulse-width ratio =
tperiod tperiod $ & ) Most mechanical systems are low-pass filters
Consider frequency components of pulse-width modulated signal
Low frequency components affect components ton They pass through average
value ton $ %& High frequency components are too fast to fight inertia
They are “filtered out” Electrical RC-networks are low-pass filters t Time constant (τ = RC) sets “cutoff” frequency
that separates low and high frequencies
" % ' - )+ ) & . % )+ ) Re...
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This document was uploaded on 04/04/2014.
- Fall '09