Keithley 7709, User Manual, Page: 5 / 33

2
Introduction
The Model 7709 is a 2-pole, 6
×
8 matrix card with the following features:
• Two rows (1 and 2) connected to the backplane of the Model 27xx for 2-wire or 4-wire
Ω
measurements
(automatically pairs switches for four wire measurements).
• 50-pin female D-shell connector (DB-50) for matrix rows and columns.
• 25-pin female D-shell connector (DB-25) for matrix expansion. Used to “daisy-chain” matrix rows to the rows of a
second Model 7709.
• Temperature applications (RTD or thermistor).
NOTE
The 7709 module can be used with Keithley Models 2700, 2701, and 2750. All references to the
Model 27xx apply to the Models 2700, 2701, and 2750.
WARNING Before operating the Model 27xx with an accessory card, verify that the card is properly
installed and the mounting screws are tightly fastened. If the mounting screws are not
properly connected, an electrical shock hazard may be present.
Card configuration – schematic
Figure 1 shows a simplified diagram of the Model 7709 matrix module. The matrix consists of 48 crosspoints. Each crosspoint
channel is a 2-pole switch that, when closed, connects a row to a column. As shown in Figure 1 , closing channel 43 connects
Row 6 to Column 3.
Two switches (channels 49 and 50) are used to connect Rows 1 and 2 to the backplane of the Model 27xx multimeter. When
channel 50 is closed, Row 1 is connected to the INPUT of the DMM. When channel 49 is closed, Row 2 is connected to
SENSE of the DMM.
Devices under test (DUT) are to be connected to the matrix columns. Using 2-wire connections, up to eight DUT can be tested.
For 4-wire connections, up to four DUT can be tested. Rows 3 through 6 can be used to add one or more external sources to the
test system.
Although the Model 7709 relays are the latching type (relays hold their state even after power has been removed), all relay
states are set to open a few seconds after either a power cycle or an *RST command is issued.