Keithley 6521, Инструкция по эксплуатации, Страница: 21 / 65

2
Card Connections and Installation
2-1
2.1 Introduction
WARNING
The procedures in this section are in-
tended only for qualified service person-
nel. Do not perform these procedures
unless you are qualified to do so. Failure
to recognize and observe normal safety
precautions could result in personal in-
jury or death.
This section includes information on making connections to
the Model 6521/22 and on installing the card in the Model
6517 Electrometer. This section is arranged as follows:
2.2 Handling precautions:
Explains precautions that must
be followed to prevent contamination to the scanner
card assembly. Contamination could degrade the per-
formance of the scanner card.
2.3 Connections:
Covers the basics for connecting external
circuitry to the scanner card.
2.4 Card installation and removal:
Summarizes the pro-
cedure to install the scanner card assembly in the Model
6517 Electrometer, outlines scanner card output con-
nections, and describes how to remove the card.
2.2 Handling precautions
To maintain high impedance isolation between channels,
care should be taken when handling the scanner card to avoid
contamination from such foreign materials as body oils.
Such contamination can substantially lower leakage resis-
tances and increase offset currents, degrading card perfor-
mance. To avoid possible contamination, always grasp the
scanner card by the side edges or covers. Do not touch board
surfaces, components, or input/output connector insulators.
Dirt build-up over a period of time is another possible source
of contamination. To avoid this problem, operate the elec-
trometer and scanner card in a clean environment. If the card
becomes contaminated, it should be thoroughly cleaned as
explained in paragraph 4.2.
2.3 Connections
This paragraph provides the information necessary to con-
nect your external test circuitry to the scanner card.
2.3.1 Model 6521 scanner card configuration
Model 6521 simplified schematic
Figure 2-1 shows a simplified schematic diagram of the
Model 6521. The scanner card has 10 input channels and a
single output. Note that each channel utilizes single-pole
switching with only the HI signal path switched. Input con-
nections include H (HI), L (LO), while output connections
include H, L, and G (chassis ground).
Figure 2-1
Model 6521 simplified s hematic
Triax
Output
BNC Inputs
H
Out L
G
H
L IN 1
H
L IN 10
IN 2....9