User's Manual

Radio/Serial Telemetry Module User Manual
Page 24 © March 2000
Repeaters can be used in a system to increase range. Each U unit can be configured to act as a
repeater. When configuring an input to be mapped to an output, the communications path to the
output unit, including the repeater addresses is specified. The U acts as a digital repeater, that is,
the signal is decoded and then retransmitted “as new”.
Example Repeater Communications
Unit A DI 1 mapped to Unit D DO1 via Units B & C
Unit A Unit B
Repeater
Unit C
Repeater
Unit D
• DI 1 is turned
on
• Transmit
• Receive
Acknowledge
• Receive
• Transmit on with
Acknowledge
• Receive
Acknowledge
• Receive
• Transmit on with
Acknowledge
• Receive
Acknowledge
• Receive
• Transmit
acknowledge
• DO 1 is
turned on
3.1.2 Change of state conditions
The module transmits a data message whenever it detects a "change-of-state" on one of its input
signals. A "change-of-state" of a digital or digital internal input is a change from "off" to "on" or vice-
versa provided the change is sustained for 0.5 second (i.e. 0.5 second debounce).
In addition to "change-of-state" transmissions, each module will transmit the status of each input to
its corresponding output every ten minutes (configurable). These updates mean that the outputs are
set to the current input values regularly, even where no “change-of-state” has occurred. These
update transmissions increase the accuracy of the output and give extra system reliability.
Analogue Change-of-state
A "change-of-state" for an analogue input, battery voltage or pulse input rate is a change in value of
the signal of 3% (configurable) since the last transmission. Note that the sensitivity of 3% refers to
3% of the analogue range, not 3% of the instantaneous analogue value. That is, if an analogue input
changes from 64% (14.24 mA) to 67% (14.72 mA), a "change-of-state" will be detected. This
“change-of-state” sensitivity is configurable between 0.8% and 50%.
Analogue inputs are digitally filtered to prevent multiple transmissions on continually varying or
"noisy" signals. The input is filtered with a 1 second time constant and a 1 second debounce. The
analogue outputs are filtered with a 1 second time constant. An example explaining the interaction of
these figures is shown below. In general, the following may be used as a rule of thumb for