Agilent Technologies Switch/Measure manual Four-Wire, One-Wire, Interlock Protection

4Low Frequency Multiplexer Switch Modules

Four-Wire

•one 20- channel 4- wire MUX. This configuration requires using neither external wiring nor connecting through the internal Analog Buses. For 4- wire resistance measurements, the instrument automatically pairs channel n on Bank 1 with channel n+20 (Bank 2) to provide the source and sense 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.

One-Wire

•two independent 40- channel 1- wire MUXes. This configuration requires neither using external wiring nor connecting through the Analog Bus relays.

•one 80- channel 1- wire MUX. You must use external wiring or connect through the Analog Bus relays for this configuration.

NOTE	Because all bank relays supply only HI signals, you can apply a
	LOW signal through COM1 L or COM2 L when you are making
	2-wire resistance measurements in 1-wire mode.

Interlock Protection

This module is interlock protected, which means whenever the D- sub connector end of the modules is exposed, the Analog Bus relays immediately open and disconnect from the Analog Buses. For more information, refer to page 96.

Overvoltage Protection

This module also features high voltage detection (< 100 V) and current limiting circuitry to protect the FET relays. This circuitry senses current flows from input overvoltages. These overvoltages may come from either the MUX input or from the Analog Buses. In addition, each channel is also protected from input overvoltages with a resistor.

When overvoltage is detected, all relays (Analog Bus and FET) are opened. While in the overvoltage state, any attempts to close any Analog Bus or FET switch, results in an error status response from the module.

Once in the overvoltage state, you must restore normal module operation with one of these actions:

•using the SYSTem:CPON <slot> command. This affects only the module specified.

128 34980A User’s Guide