Keithley 7020 Instruction Manual - page 19
Card Connections and Installation
2-3
2.4
Pull-up resistors
When interfacing outputs to high-impedance devices (i.e.
logic devices), pull-up resistors are used to achieve the ap-
propriate logic level. These resistors are installed at the fac-
tory. When interfacing digital output channels to pull-up
devices, such as solenoid coils and motors, the pull-up resis-
tors for those channels have to be removed.
The 40 output channels are divided up into fi e banks (eight
output channels per bank). Each output bank has a 16-pin
DIP socket that is used for a thick film resistor network. Each
thick film resistor network has eight resistors to accommo-
date the eight output channels. Thus, when you remove a re-
sistor network, you remove the pull-up resistors for eight
output channels.
Table 2-1 indicates the resistor network for each bank of out-
put channels.
The resistor networks (R180 through R181) are located on
the scanner board (see Figure 2-2). To remove a resistor net-
work, use a thin-bladed screwdriver and carefully pry the
chip out of the socket. Pull-up resistors should be replaced
with same value and wattage only.
2.5
Card installation
Perform the following steps to install the card assembly in
the Model 7001 or 7002 mainframe:
WARNING
Turn off power from all instrumentation
(including the Model 7001 or 7002
mainframe) and disconnect their line
cords. Make sure all power is removed
and any stored energy in external cir-
cuitry is discharged.
1. Mate the mass terminal board to the scanner board if
they are separated. Install the supplied 4-40 screw at the
end of the card to secure the assembly. Make sure to
handle the cards by the edges and shields to prevent
contamination.
2. Facing the rear panel of the mainframe, select the slot
that you wish to install the card in.
3. Feed the I/O card assembly into the desired slot such
that the edges of the relay card ride in the rails.
4. With the ejector arms in the unlocked position, push the
card assembly all the way into the mainframe until the
arms engage into the ejector cups. Then push both arms
inward to lock the card into the mainframe. Figure 2-4
shows how the card installs in the Model 7001.
5. Install and tighten the safety ground screw shown in
Figure 2-4.
WARNING
To avoid electric shock that could result
in injury or death, make sure to properly
install and tighten the safety ground
screw shown in Figure 2-4.
Table 2-1
Pull-up resistors identificatio
Bank
Output
channels
Resistor
network
A
B
C
D
E
1 - 8
9 - 16
17 - 24
25 - 32
33 - 40
R180
R181
R182
R183
R184
JUMPER
5.3V
V
EXT
A. 5.3V Source Selected
JUMPER
5.3V
V
EXT
B. External Source Selected
Figure 2-3
Voltage source jumper installation