Keithley 3720 Test Accessory, Multiplexer Card

The Keithley 3720 Test Accessory, Multiplexer Card is a plug-in module designed for Keithley Series 3700 and 3700A mainframe systems. It has two independent banks of 1×30 two-pole multiplexers that reconfigure to function as a single 1×60 two-pole multiplexer, 30 four-pole channels, or enable card-to-card expansion. The card employs latching electromechanical relays with relay closures stored in onboard memory, delivering scan rates exceeding 110 channels/s.

Technical Specifications

• Channel Configuration: Dual 1×30 two-pole multiplexers (60 two-pole or 30 four-pole channels total)


• Switching Voltage Capacity: 300 V DC or 300 VRMS


• Switching Current Capacity: 1 A


• Carry Current Capacity: 2 A


• Power Dissipation: 60 W


• Apparent Power: 125 VA


• Scan Rate: >110 channels/s


• Temperature Measurement Accuracy (with 3720-ST): 1°C for J, K, T, and E thermocouple types


• Hazardous Voltage Threshold: >30 VRMS, 42.4 V PEAK, or 60 V DC

Key Features

• Latching electromechanical relay architecture with memory-based closure retention


• Flexible reconfiguration supports two-pole, four-pole, and expansion modes


• Two 78-pin male D-sub connectors for signal routing


• Backplane relays enable bank and card-to-card interconnections with interlock safety disabling


• Compatible with 3720-ST screw terminal block for automatic cold junction compensation in thermocouple applications


• Operating temperature range: 0°C to 50°C at 70% RH (35°C)


• RoHS compliant; conforms to EN61010-1 and EN61326-1

Typical Applications Multiplexed signal routing in automated test systems, thermocouple temperature measurement with automatic CJC, multi-channel data acquisition and switching, and modular test system expansion.

Compatibility & Integration Compatible with Keithley Series 3700 and 3700A mainframe systems. Optional 3720-ST screw terminal accessory enables automatic CJC for thermocouple measurements. The 3720-MTC-3 cable assembly (3.0 m) with 78-pin D-sub connectors provides external connectivity.