Error message: “The connection to the instrument was lost.”

Created on 2009-05-12 22:41:00


I periodically receive an APx500 error saying “Connection to the instrument was lost.”

APx Connection Lost error.

I then have to close and restart the software to continue working. Why is this happening?


APx hardware transmits large amounts of data over USB, and therefore any USB impairments can cause connection issues. For best performance, we recommend that you connect the instrument directly to a USB port on the PC, and that you don’t put other USB devices on the same root hub. On modern PCs, each port is usually supplied by a separate root hub. You can verify that the root hub with the APx analyzer is not being shared by looking at the USB Root Hub Properties in Device Manager.

Device manager showing USB Root Hubs. A modern PC may have twelve or more Root Hubs on the motherboard.

Power tab shows the APx500 analyzer drawing zero mA, with four ports available

USB Root Hub Properties window, Power tab. The APx analyzer is the only device on this root hub.

If you must put other devices on the same hub as the APx:

  1. Avoid sharing with USB 1.1 devices, like a mouse and keyboard. Some old hubs reduce the upstream transfer rate to USB 1.1 speed if there are any such devices connected.
  2. On external hubs, use a powered type (one that has its own plug-in power supply). Unpowered hubs have to divide the available current on their upstream link to all their ports, which may not be sufficient to operate those devices and the hub itself properly.
  3. On a powered hub, avoid connecting too many high current devices. A powered hub can provide up to 500 mA to each port, but usually not to all of them simultaneously. Although APx instruments draw no current from the USB bus, if the hub power supply is overloaded by other devices, the hub may shut down or not operate properly.

Connection problems can also result from:

  1. Poor quality cables
  2. Cables that are too long (over 5 meters / 16.4 feet)
  3. Intermittent power to the analyzer
  4. PC that is too slow (minimum requirement 2 GHz or faster processor, 2 GB or more RAM)
  5. Running other programs simultaneously that have high processor or memory usage