Vaisala DM500 - Manual (Page 81)

Chapter 14 _________________________________________________________ Output Interfaces
VAISALA _______________________________________________________________________ 79
All the modes selected: relay function is not dependent on any
measurement mode.
None of the modes selected (never): relay function is disabled.
You can select any combination of the measurement status.
Example: If you want to have relays working on the basis of the
STOP and ERR mode to know when the measurement data is
not valid, delete the setpoints and select enabled when: STOP
and ERR mode.
11. Press EXIT to return to the main view.
12. Set the other relay similarly.
13. You can test the relay operation with the Relay test button.
Relay is forced to change state as long as you press the Relay
test button.
Relays can be configured also by using the serial line (see command
RSEL).