I don't understand why you don't get any response. It seems that the instrument does not get or recognize the command.
You said the serial port utility is working, with the same hardware I guess?
You may install a serial port analyzer to view what's actually sent over the line when using the utility. See for example here, there are many other though.
Here is a list of other possible problems:
- serial port settings (for example baud rate, but not only) are wrong
- instrument address is wrong (zero is often used as a broadcast address, you may try it)
- your RS485 port is an adapter plugged into a RS232 and needs the RTS line to be high to enable transmission
- the manual is wrong and you need \r instead of \n to terminate the command
I use \r to terminate the command and it works! Thanks for your help!