The Keithley 3761 provides quality low-current switching at an affordable price. The offset current error generated is specified. The offset current error generated is specified <1pA, with a typical performance at <30fA. When used with a voltage source and an electrometer or picoammeter, this card can easily automate insulation resistance tests, reverse leakage tests on semiconductor junctions, or gate leakage tests on FETs.

The Keithley 3761 features both current and voltage modes. In the current mode, the current path is maintained even when the channel is open. This eliminates cable charging time between measurements. In voltage mode, the input is broken and is high impedance. Input connectors are SMA for shielding sensitive measurements. An SMA male to BNC male cable (3761-BNC-SMA) is available for compatibility with existing 7158 configurations and with Keithley accessory cables such as the 4801 and 4803. The 3761 does not connect to the 6 common buses on the 3706A backplane, but two outputs are provided to allow for chaining several scanner cards to one measurement instrument, allowing up to 60 channels, while an isolation relay in the output HI minimizes interaction between cards.