User's Manual

905U-K Radio Telemetry Module User Manual
 ELPRO Technologies Pty Ltd 2001 Page 10
2 OPERATION
2.1 Normal Operation
Once configured using the 905U-K configuration software, the 905U-K module will normally
be in “sleep” mode to conserve power. During sleep mode, the microprocessor controller
powers down, and the analogue loop supply is turned off. The microprocessor will
automatically “wake up” and revert to full operation if a digital/pulse input changes (on to off,
or off to on), or every 0.5 seconds to check if a timed update transmission is due to be sent.
Normal operation of the 905U-K is indicated by a brief flicker of the OK LED light on the
front panel approximately every 10 seconds.
2.2 What information is transmitted over the radio?
The 905U-K modules transmit the value of the input signal in a data frame. The data frame
includes a system address, and the "address" of the transmitting (source) 905U-K module and
the receiving (destination) 905U module, so that each transmitted message is acted on only by
the correct receiving unit. The system address is a common address used by all modules in the
same system. This allows multiple systems to operate within the same radio range without
"cross-talk" between systems.
The user configures these addresses as part of the module configuration. Each transmitted
message also includes error checking to ensure that no corruption of the data frame has
occurred due to noise or interference. If repeater modules are being used, then the addresses
of these intermediate modules are also included in the data frame.
The user can configure the 905U-K to transmit each message from one to five times to ensure
that at least one of the messages is received correctly. Each repeat transmission will occur at
random intervals between one and four seconds.
2.3 How often is the input information sent by radio?
• Change messages. The 905U-K transmits the value of an input signal whenever the signal
changes.
• Update messages. The input value is also transmitted if the signal has not changed within a
pre-configured update time (configurable 10 seconds to 5 days).
• Paralysis. When a 905U-K transmits a message for a particular input, the 905U-K will not
transmit another message for this input within a configured time period. This time is called
the paralysis time, and may be used to prevent a lot of messages being transmitted if an
input changes frequently. The paralysis time may be set from zero to 127.5 seconds for
each input. For example, assume the paralysis time on an input is 30 seconds. If the
input changes, then the 905U-K will transmit a message, however it will not transmit
another message for this input during the next 30 seconds, regardless of changes to the
input signal. Note that paralysis time does not stop re-transmissions of each message - if
the 905U-K is configured to transmit each message three times, then paralysis will not
stop this.
Depending on the type of input signal (digital, pulse or analogue), the 905U-K must determine
what type of signal change is required to send a transmission: