Theory of Operation
Introduction2
2-1. Introduction
Chapter 2 provides the theory of operation for the Fluke 88.
An overview of circuit operation is presented in the form of functional block
descriptions. Detailed circuit descriptions cover the major circuit functions in more
detail. Schematic diagrams are in Chapter 5.
2-2. Functional Block Description
Figure 2-1 is a block diagram of the Fluke 88 Automotive Meter. The Meter is
partitioned into analog and digital sections. The integrated meter chip (U4) performs
both analog and digital functions.
The analog section of U4 contains the analog-to-digital (a/d) converter, active filter, ac
converter, frequency comparator, analog signal routing, range switching, and power
supply functions.
The digital logic portion of U4 provides the state machine for synchronous a/d converter
control and the 16-bit counter used for a/d converter counts and frequency
measurements. Also, the digital logic section contains bus and interrupt control circuits
(to facilitate the microcomputer interface) and registers for analog switch drive.
The microcomputer section of U4 executes software functions, formats data for the
display, drives the display, and controls most analog and digital logic functions. The
pushbuttons initiate various operating modes for the microcomputer. Output from the
microcomputer can be presented visually on the liquid crystal display (LCD) and audibly
by the beeper.
2-3 |
ACEC
