Vaisala DMT340 User Manual download pdf (Page 103)

Chapter 4 _________________________________________________________________ Operation

VAISALA _______________________________________________________________________ 101

Outputting Reading Once From All Transmitters

Use the DSEND command to output the reading once from all connected

transmitters that are in STOP or POLL modes. In order to avoid data

collisions, the transmitters will send their response after a suitable delay.

The response includes the transmitters’s address, followed by their

measurement message.

NOTE

The total execution time of the

DSEND command depends on the bit rate

of the serial port connection. At slow speeds, it will take a considerable

amount of time for devices with large address number to

respond. The

delay will be the same even if there are no other devices at all.

DSEND<cr>

Example (transmitters with addresses 3 and 25 responding):

>dsend

3 Tdf= -5.8 'C H2O= 3715 ppmV x= 2.3 g/kg

25 Tdf= -1.1 'C H2O= 5549 ppmV x= 3.5 g/kg

Communicating with a Transmitter in POLL

Mode

OPEN

When all transmitters on the RS-485 bus are in POLL mode the OPEN

command sets one transmitter temporarily to STOP mode so that other

commands can be entered.

OPEN [aa]

where

Address of the transmitter (0 ... 255)

The CLOSE command switches the transmitter back to the POLL mode.

Example:

>OPEN 2 (opens the line to transmitter 2, other

transmitters stay in POLL mode)

>CRH (for example, calibration performed)

...

>CLOSE (line closed)

1 2 ... 98 99 100 101 102 103 104 105 106 107 108 ... 190 191

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Vaisala DMT340 User Manual Page 103