The Keithley 7708 Differential Multiplexer Module delivers high-density signal routing with 40 differential channels for data acquisition systems. Each channel supports two-wire or four-wire measurement configuration, enabling flexible sensor integration across temperature, resistance, and voltage applications. The module features latching electromechanical relays with onboard memory to retain closure states, plus integrated Cold Junction Compensation sensors for accurate thermocouple linearization. Designed for Keithley mainframes including Models 2700, 2701, and 2750, it combines low-noise signal integrity with simplified field wiring via oversized screw terminal blocks.
Technical Specifications
Signal Handling
• 40 differential channels, configurable as two independent 20-channel banks
• Two-wire and four-wire measurement modes
• Maximum signal: 300V DC/RMS, 1A switched, 60W / 125VA
• Minimum signal: 10mV, 10µA
• Contact potential: <±500nV typical per contact pair, 1µV maximum
• Offset current: <100pA
• Relay actuation time: <3ms
• Contact resistance: <1Ω to 10¹⁰Ω, 10⁹Ω, <200pF
• Common mode voltage: 300V between terminal and chassis
• Crosstalk (10MHz, 50Ω load): <-40dB
• Insertion loss: <0.1dB below 1MHz; <3dB below 2MHz (50Ω source/load)
Temperature Measurement
• Automatic Cold Junction Compensation with integrated sensors
• Temperature accuracy via internal CJC: 1.0°C
– Key Features
• Latching relays with state memory retention
• Oversized screw terminal blocks for #20 AWG wire
• Low contact potential and offset current for sensitive measurements
• High isolation suitable for mixed-signal applications
• Compact form factor: 0.52kg
– Typical Applications
Multi-point temperature monitoring, environmental stress screening, mixed-signal testing, RTD and thermistor measurement, thermocouple linearization.
– Compatibility & Integration
Operates with Keithley Model 2700 (rev. A02 or B01), 2701 (rev. A01), and 2750 (rev. A01 or higher) mainframes.
