Keysight 34921A User Manual

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Keysight 34921A User Manual Manual pdf 41 page image

40 Keysight 34921A-34925A Low Frequency Multiplexer Modules User’s GuideLow Frequency Multiplexer Modules 34924A 70-Channel Reed Multiplexer34924A 70-Channel Reed MultiplexerThe high-density 34924A 70-Channel Reed Multiplexer (70-Ch Reed MUX) isdivided into two banks with 35 non-latching reed switches (channels 1-35 and36-70) 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 bankrelays to the system Analog Buses. Through ABus1 and ABus2 you can connectany of the channels to the system DMM for voltage or resistance measurements.See the simplified schematic on page 42.Using program commands or the mainframe front panel, you can control each ofthe channel switches individually, and thus configure the 34924A in any of thesemodes:- two independent 35-channel 2-wire MUXes. This configuration requiresneither using external wiring nor connecting through the internal AnalogBuses.- one 70-channel, 2-wire MUX. You must use external wiring or connectthrough the internal Analog Buses for this configuration.- one 35-channel 4-wire MUX. This configuration requires neither usingexternal wiring nor connecting through the internal Analog Buses. For 4-wireresistance measurements, the instrument automatically pairs channel n onBank 1 (source) with channel n+35 on Bank 2 (sense) to provide theseconnections. Four-wire controls occur only when doing 4-wire measurementoperations through the internal DMM, such as MEASure:FRESistance? orscanning a channel previously configured as 4-wire.In 2-wire mode, you can close no more than 20 channels simultaneously due topower dissipation. These 20 channels are split 10 to a bank. However, note thatAnalog Bus relays count half as much as channel relays in that total. Forexample, with one Analog Bus relay closed, you can close up to a maximum of 19channel relays. If you try to close more than the allowed number of channels, youwill receive an error message.In all modes, this module has capability to scan as many as 500 channels/secondusing the internal DMM. With the automatic “break-before-make” connectionoperation, you are assured that no two signals are connected to each otherduring a scan.Because user-attached reactive loads and backplaneparasitic capacitance may result in high in-rush currents,100 in-rush resistors protect the reed relays from damageand performance degradation. Therefore, you must considerthese resistors when you are designing a measurement.Refer to the simplified schematic on page 42.Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com