34924A 70-Channel Reed Multiplexer - Agilent Technologies 34921A User Manual

34924A 70-Channel Reed Multiplexer

The high- density 34924A 70- Channel Reed Multiplexer (70- Ch Reed MUX)
is divided into two banks with 35 non- latching reed switches (channels
1- 35 and 36- 70) in each. This module also contains eight armature Analog
Bus relays (channels 911- 914 and 921- 924), four on each bank that can
connect the bank relays to the system Analog Buses. Through ABus1 and
ABus2 you can connect any of the channels to the system DMM for voltage
or resistance measurements. See the simplified schematic on
Using program commands or the mainframe front panel, you can control
each of the channel switches individually, and thus configure the 34924A
in any of these modes:
• two independent 35- channel 2- wire MUXes. This configuration requires
• one 70- channel, 2- wire MUX. You must use external wiring or connect
• one 35- channel 4- wire MUX. This configuration requires neither using
In 2- wire mode, you can close no more than 20 channels simultaneously
due to power dissipation. These 20 channels are split 10 to a bank.
However, note that Analog Bus relays count half as much as channel relays
in that total. For example, with one Analog Bus relay closed, you can close
up to a maximum of 19 channel relays. If you try to close more than the
allowed number of channels, you will receive an error message.
In all modes, this module has capability to scan as many as 500
channels/second using the internal DMM. With the automatic
"break- before- make" connection operation, you are assured that no two
signals are connected to each other during a scan.
Agilent 34921A-34925A Low Frequency Multiplexer Modules User's Guide
neither using external wiring nor connecting through the internal
Analog Buses.
through the internal Analog Buses for this configuration.
external wiring nor connecting through the internal Analog Buses. For
4- wire resistance measurements, the instrument automatically pairs
channel n on Bank 1 (source) with channel n+35 on Bank 2 (sense) to
provide these connections. Four- wire controls occur only when doing
4- wire measurement operations through the internal DMM, such as
MEASure:FRESistance? or scanning a channel previously configured
as 4- wire.
Because user-attached reactive loads and backplane parasitic
C A U T I O N
capacitance may result in high in-rush currents, 100
resistors protect the reed relays from damage and performance
degradation. Therefore, you must consider these resistors when
you are designing a measurement. Refer to the simplified schematic
on page
34924A 70-Channel Reed Multiplexer
29.
page 29.
Ω
in-rush
27