Instructions

UM-0085-B09 DT80 Range User Manual Page 300
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Sleep Mode
The DT80 has a low power sleep mode that significantly reduces the power consumption – to as low as 2 mW when
running from the internal battery. While asleep no measurements or processing can be done, but the state of the current
job is preserved. The DT80 will automatically wake from sleep when a measurement is due, or some other event occurs.
About Sleep Mode
While the DT80 is asleep:
• The LCD and all front panel LEDs are switched off.
• All communications ports (Ethernet, USB, serial) are disabled. Any USB or TCP/IP connections will be
disconnected when the logger goes to sleep and will need to be re-established by host software after the logger
wakes.
• Digital output states and the state of the latching relay are maintained.
• Digital inputs are not scanned – transitions will not wake the logger, trigger schedules or be counted by low
speed counter channels (1..4C channel types).
• Pulses on the high speed counter inputs (1C-4C terminals, 1..4HSC channel types) will be counted, without
waking the logger. As discussed in Counting While Asleep (P339), it is necessary to wake the logger
periodically using a timed schedule to ensure that the 16-bit hardware counters do not overflow.
• The 12V/5V power output is switched off.
• The PWR OUT power output will still be available, assuming that the logger is externally powered.
• All parameter settings, CV values, comms port settings and other job-related state information is preserved.
Wake Events
Once asleep, the DT80 will stay that way until one of the following events occur:
• a timed schedule becomes due
• a modem communications session time window becomes due
• a modem/Ethernet communications session retry is due
• a keypad button is pressed
• the WK (wake) input terminal is pulled to logic low
• a character is received on the serial sensor port, or there is a transition on the CTS line
• external power is connected
• a USB communications cable is connected
• a character is received on the host RS232 port
Any of these will cause the DT80 to wake. If the reason for waking was a timed schedule, the DT80 will execute the
schedule, then immediately go back to sleep (if there are no other schedules due within the next few seconds). During
this time the LCD and backlight will remain off.
For all other wake sources, the DT80 will stay awake for at least the period specified by parameter P17 (default 30s).
This timer will be reset if any further wake events occur, or if data is received on any comms port. Once the timer expires
the DT80 will go back to sleep.
Also that:
• Event triggered schedules (i.e. schedules triggered by digital input transitions, counters, serial data or CV
values) will not
cause the logger to wake. Only timed schedules will cause a wake up.
• If the DT80 is woken by receipt of RS232 data on the host or serial sensor port, the first character (and possibly
some of the following ones) will be lost. You should therefore always send a dummy character (e.g. LF) to wake
the DT80, then wait about one second before sending the first actual command.
Controlling Sleep
By default, the DT80 will not go into sleep mode if any of the following are true:
• a schedule or command is being executed, or is due to execute soon
• the Ethernet port is enabled and a cable is connected
• a USB cable is connected
• a PPP session is currently active
• a modem or Ethernet communications session is active
• a job has been partially entered
• there has been "activity" (e.g. key press, command, Modbus/ web/ FTP request) within the last P17 seconds