In case a device can not be autodetected or connection to a specific device is required, is is possible to specify the connection explicitly as an driver option, using the "<driver-name>:conn=<connection>" syntax.
Most multimeters use a serial connection. The corresponding device cables either povide an RS232 connection or an USB connection using an serial to USB-CDC or serial to USB-HID converter chip, see Serial port. Some devices are available with different data cables. RS232 and USB-CDC (Virtual Com Port, VCP) cables use a common driver, USB HID cables need a seperate one. If a device has two drivers, the one for RS232/VCP is typically suffixed with "-ser"
RS232 / Virtual Com Port
<device-path> is an absolute path to the wanted device, e.g. /dev/ttyUSB1 or /dev/ttyACM0.
$ sigrok-cli --driver=uni-t-ut61e-ser:conn=/dev/ttyUSB0 -O analog
USB HID connections
<vendor-id> and <product-id> have to be specifid as 4 hexadecimal digits.
<bus-nr> is an integer betwenn 1 and 255, <device-address> is an integer between 1 and 127. The device address changes every time a device is reconnected. Bus number and device address can e.g. be found using lsusb.
$ sigrok-cli --driver=uni-t-ut61e:conn=1a86.e008 -O analog $ sigrok-cli --driver=uni-t-ut61e:conn=2.12 -O analog
Devices using SCPI
SCPI has several backends. For all backends but serial the backend name is the first parameter, followed by one or more backend specific parameters.
Serial / Virtual Com Port
Same syntax as for DMMs with serial connection.
$ sigrok-cli --driver=hameg-hmo:conn=/dev/ttyACM0 -O analog -frames 1
Similar syntax as for DMMs with USB HID datacables.
$ sigrok-cli --driver=hameg-hmo:conn=usbtmc/0aad.0119 -O analog -frames 1
$ sigrok-cli --driver=hameg-hmo:conn=tcp-raw/192.168.1.20/5025 -O analog -frames 1
Vendor specific protocols
Most (all?) devices using a vendor specific protocol use either RS232 or a USB-to-serial converter, thus the connection string is the same as for DMMs with serial connection.