Chapter hvac engineering Fundamentals: Part 1 Introduction

8.3.2
Controllers
Controllers may be classified by the type of control action and type of
energy used for the control signal. Control action may be two-position
or modulating, with modulating control utilizing proportional, inte-
gral, or differential modes or some combination of these. Control en-
ergy sources include pneumatic, hydraulic, electric, electronic, and
self- or system-generated. The continued development of transistor
technology into microchip technology with programmable control adds
the words
analog
and
digital
to the vocabulary.
Analog
suggests con-
tinuous modulation of a signal by voltage or current flow, while
digital
Design Procedures: Part 6
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