Introduction; Functional Block Description; Detailed Description; Voltage Signal Conditioning - Fluke 77 Series III Service Manual

2-1. Introduction

This chapter contains a brief overview of the 77 Series III Multimeter,
followed by a more detailed explanation of operation.

2-2. Functional Block Description

The heart of the instrument consists of a two-chip CMOS system: U1, a
primarily analog IC, and U2, a calculator-style microcomputer (see Figure 2-
1).
Input
Signal
Conditioning
J1
V
REF
A/D
Y1
Counter
32.768
kHz
U1 Analog Chip

2-3. Detailed Description

The following paragraphs describe the 77 Series III Multimeter in more detail.
While reading this description, refer to the schematic diagram in Chapter 5.
2-4.

Voltage Signal Conditioning

Input divider Z1 and dc blocking capacitor C1 make up an input voltage signal
conditioning circuit.
S1
To Bar
Graph
Range and
Function
Control
A/D Samples
Figure 2-1. Overview
Theory of Operation

Introduction

LCD
To Digital
Display
U2 Microcomputer
aaa01f.eps
2
2-3