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The service port is intended for a temporary connection to the transmitter. You can use it for configuration, calibration, and troubleshooting using a computer.
The RS-485 line of the service port is shared with the connection to RS-485 Modbus output; the M8 service port connector is just an additional connector for easier access. Before plugging in the Vaisala USB cable (219690) to the service port, perform the following steps:
- Open the cover of the HMDW110 series transmitter.
- If the terminal block for terminals 5 ... 8 is wired, pull it out. This disconnects the transmitter from supply voltage and prevents possible equipment damage that may be caused by ground loops. The locations of the terminal blocks and the service port are shown in HMDW110 series component boards.
- If the other terminal block is wired (terminals 1 ... 4), pull it out also. This prevents the communication between the transmitter and the Modbus (RS-485) host from interfering with your connection.