Keithley 7701, Руководство пользователя, Страница: 7 / 33

2 Model 7701
Introduction
The Model 7701 is a 32-channel high speed differential multiplexer module with the following features:
• 2-wire or 4-wire
Ω
measurement (automatically pairs switches for four wire measurements — n +
16).
• Temperature applications (RTD or thermistor).
• 50-pin female D-Shell connector (DB-50) for channels 1 through 24.
• 25-pin female D-Shell connector (DB-25) for channels 25 through 32.
• Screw terminals and supplied jumpers to access the DMM of the
Model 2700/2750.
WARNING The Model 7701 is configurable to be connected to the internal DMM via the supplied
jumpers and the screw terminals. When connected to the internal DMM, all other mod-
ules must be derated to 150VDC or 150Vrms (212V peak) for AC waveforms.
NOTE
The Model 7701 is shipped from the factory with the screw terminal jumpers NOT installed. See
“Screw terminals” to install the jumpers.
Card configuration – schematic
Figure 1 shows a simplified schematic diagram of the Model 7701 module. As shown, the Model 7701 has
input channels that are grouped into two banks of sixteen channels (thirty-two channels total). A backplane
isolation relay is provided for each bank. The first bank contains channels 1 through 16 while the second
bank contains channels 17 through 32. Each input channel of the 32-channel multiplexer card is wired with
separate inputs for HI/LO providing fully isolated inputs.
As shown in Figure 1 , all Model 7701 channels are isolated from the DMM of the Model 2700/2750 by
screw terminals. Supplied jumpers must be installed in the screw terminals to connect switching module
channels to the DMM.
For added flexibility, the Model 7701 is equipped with four extra screw terminals. These user-configurable
screw terminals are hard-wired to the female DB-25 connector of the switching module. These screw termi-
nals allow external input to bypass the switching module channels.