OMC-042 / 043 / 044 Data loggers
Users
’ manual
page 57
DTU Connection (OMC-043/044 only)
A Remote Data Terminal Unit (DTU) is a communication device making it possible to form a wireless
(GPRS/UMTS) transparent communication channel between a "legacy" serial device and modern TCP
(internet) enabled host software. A DTU is similar to the well-known classic or cellular MODEM, but has
several advantages regarding scalability, performance and operating costs. A DTU based system is more
scalable, because the host does not require multiple MODEMS to be able to connect to multiple remote
locations simultaneously, in fact the host does not need a MODEM at all and can serve lots of incoming
DTU (TCP-client) connections simultaneously. Data communication over GPRS or UMTS is faster and
less expensive than data communication over GSM.
Our DTU (sometimes referred to as RTU) is not a separated product, but an integral part of our /OMC-
043/OMC-042 Low Power Data Logger functionality. Because our Data Loggers are low power and self-
sustaining, the RTU function can be used to monitor "legacy" serial devices at remote locations with no
access to a power grid or external power source. The RTU function can be programmed to wake-up at a
regular interval or on alarm (e.g. an external digital interrupt). At wake-up the DTU switches on the power
to the serial device, connects to the TCP-server and forms a transparent serial data channel between
serial device and host (TCP-server). The transparent channel will be broken after expiration of a certain
timeout or when the host drops the TCP-connection. After braking the transparent channel, the DTU will
remove the power from the serial device (to prevent the device consumes power unnecessarily) and
returns to low power sleep again.
Mobile connected internet devices have fixed IP-addresses seldom and most legacy serial devices don't
have a provision (in their protocol) to uniquely identify themselves. Obviously a host (TCP-server) wants
to know where the connecting DTU (TCP-client) originates from and to assist the host to determine it, the
DTU can be configured to send an identification string first before forming a transparent communication
channel.
Below the settings menu is displayed:
DTU settings
[0] Exit
[1] Name >> DTU
[2] Port settings >> RS232 8N1; 9600 Baud
[3] Sensor power switch >> Disabled
[4] Connect interval >> 06:00:00
[5] Connection delay >> Not used
[6] Server >>
[7] TCP port >> 37
[8] Client ID >>
[9] Termination ID >>
[A] Terminal request ID >>
[R] Remove
[T] DTU test >> Not done
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