Chapter Three Operation
man_905-105_2.16 Page 31
In general, the following may be used as a rule of thumb for calculating the appropriate sensitivity
required for a given application:
Instantaneous change of 2 x sensitivity on input → 3 second output response
Instantaneous change of 10 x sensitivity on input → 5 second output response
The analog inputs have 15 bit resolution and 0.016mA accuracy.
Pulse input change of state
Pulse input counts do not use “change-of-state” transmissions. Instead, accumulated pulse input
counts are transmitted at set intervals. The default period is 1 minute and is configurable. The absolute
pulse count is transmitted. If the PI is transmitted to a PO on a 905U/105S module, then the pulse
outputs are re-created from the accumulated pulse count. Rollovers of the pulse count thru zero are
catered for. If a transmission is missed, the pulse output will still be re-created when the next
accumulated value is transmitted. This ensures that no pulses are lost due to communications failures.
If the PI is transmitted to a 905U-C interface module, then the accumulated pulse count is stored in the
905U-C for interfacing to the host device.
The following diagram shows how pulse inputs are re-created as pulse outputs. For pulse outputs, the
module keeps two counters in memory - the pulse input count received from the remote module, and
the count of output pulses. When the receives an update of the input pulse count, it will output pulses
until the output pulse count is the same as the input pulse count. The output pulse will be output
evenly over the pulse output update time which is configured in the module. For example, assume that
module receives a pulse input update message from the remote module, and the difference between the
pulse input count and the pulse output count is 12 pulses. The module will then output the 12 pulses
evenly over the next minute (if the pulse output update time is 1 minute).
The default values for the pulse input update time and pulse output update time is 1 minute. In this
case, the output pulses are effectively 1 minute behind the input pulses. These update times may be
changed by the user. The pulse output update time should not be set to be more than the pulse input
update time. Note that the maximum pulse rate for both inputs and outputs is 100Hz.
As well as accumulating the pulse input, the module will also calculate the rate of pulses. Pulse rates
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