The Optimus/Optimus+ sound level meters appear under Windows as a USB mass storage device, very much like a USB drive. If the configuration is correct, the Optimus/Optimus+ will be available within NoiseTools and you will be able to connect to the instrument, configure it and download measurements.
If Windows has installed the wrong device driver or has misidentified the Optimus/Optimus+ sound level meter as another device, the instrument may not connect to NoiseTools.
This can occur either when connecting an Optimus/Optimus+ to a PC for the first time or after a Windows update when drivers may have been updated.
The following technical note shows how to diagnose and resolve USB connectivity issues between an Optimus/Optimus+ or Trojan sound level meter and the PC that is running the NoiseTools software:
Technical Note 64 Optimus USB troubleshooting