In most cases, connecting peripherals to a PC is not a problem. The fact that a USB stick, for example, has the same ground potential as a laptop is hardly a problem. But when it comes to measuring devices connected via USB, the situation is different. Here, electrical isolation protects the PC from potentially harmful voltages. Isolation also helps to avoid ground loops. Specific chips are available for this purpose. The circuit presented here uses such a chip to provide electrical isolation for a USB connection.

Unlike in the past with GPIB, these days the individual devices in automatic test setups are usually controlled via USB. Since ground loops have always been a problem, GPIB had special devices for electrically isolating the control unit (usually a PC) from the measuring instruments and generators connected to it. Unfortunately, the transition to USB has not changed this challenge. This is because there is also a ground connection between the devices, and it is not uncom...