User's Manual

Radio/Serial Telemetry Module User Manual
Page 42 © March 2000
• Update Times
• Analogue Sensitivity
• Reset Output on Comms Fail
• Digital/Analogue Debounce (905-1 and 905-2 only)
• Analogue Debounce (905-2 only)
• Set-points (905-1 and 905-2 only)
• Pulse Rate Scale (905-1 and 905-2 only)
• Pulse Output Update (905-1 and 905-3 only)
Update Times allows configuration of how frequently each configured mapping is updated
(Integrity Update).
The period of update (check) transmissions may be configured individually for each input. The
default period is 10 minutes for all inputs, except for pulse inputs (1 minute). Note that this is the
check transmission time - updates will also be sent on any change-of-state on each input. It is
important here to keep in mind the principle - “Less radio traffic means better communications”.
Short update times should only be used in special circumstances, or when an RS-485 network is
used, and the message is not transmitted over a radio link. Frequent updates from multiple units
causes congestion of the radio channel, which results in increased communication failures and
general performance degradation of the system.
Analogue Sensitivity allows configuration of the change required in an analogue input before a
“Change Of State” is detected, and the new analogue value is transmitted. For input signals which
vary widely over a short period of time or have a normal oscillation, the analogue sensitivity should
be set to an appropriately large value. This ensures that many change messages are not transmitted
in too short a time. This will result in channel congestion, as described in the preceding section.
Reset Output on Comms Fail allows the Comms Fail Time to be selected - this is the time for
an output to reset if it has not received an update or change message.
Each output on the unit, either analogue or digital, may be configured to reset (off or 0mA) when no
update transmission has been received for a certain time. The default condition is zero (no reset).
This option can be used to ensure that communications failure will not result in loss of control. For
example, outputs connected to pumps should be configured to reset on communications failure so
that the pump will turn off.
If the reset time is less than the update time, then the output will reset when the reset time expires,
and then set again when the update message is received. We recommend that the reset time be a
little more than twice the update time.
Debounce is the time which an input must stay stable before the 905 module decides that a change
of state has occurred. If the input changes (say 0 → 1) and changes again (1 → 0) in less than the
debounce time, then the 905 module will ignore both changes. Debounce may be configured for
digital inputs on the 905-1 and 905-2 modules (0.5 - 8 seconds) and the analogue inputs on the