6-Wire Guard and Current PXI Amplifier Module—The PXI-4022 consists of a high-speed, high-precision amplifier that conditions signals for acquisition. With the guarding functionality, you can make 6-wire resistance measurements for resistors connected in parallel on complex printed circuit board layouts or cable test applications. For low-current measurements, the PXI-4022 amplifier and high-precision resistors create a feedback current amplifier. This implementation minimizes burden voltages and converts current to voltage, so you can measure picoampere signals with femtoampere noise.