WI-I/O 9-K
v1.9
Page 14
Overview:
•
Pulse inputs are counted as 2 x 16 bit registers.
•
Pulse count is transmitted when the count has increased by the sensitivity amount since the
last transmission.
•
Update message if the input value has not been transmitted within the update time (10
seconds - 7 days).
•
After each transmission, another transmission for that input is disabled for the paralysis time
(0 – 127.5 sec).
•
PI2 can be scaled by a configurable divider.
The diagnostics functions of the WI-I/O K allow the user to manually set the counter values to
any value (refer section 5 of this manual). On initial start-up of the modules, the counter values
will be zeroed. If the module loses power, the WI-I/O K will save the counter values to non-
volatile memory before shutting down - these values will be restored when power is restored.
2.4.3
Shaft Encoder Inputs
The two pulse inputs may be configured to control one up/down count value, for use with
quadrature and incremental shaft encoders. A shaft encoder is a transducer that measures level or
displacement, and has two pulse signals to indicate change of level and direction of change. Both
pulse inputs are read at the same time. The divider parameter on PI2 must be set to 1 for this
application.
If an incremental encoder is used, then the calculated count value is stored in PI1. If a
quadrature encoder is used, then the calculated count value is stored in PI2.
The counter value (or “level position”) can be manually set using the WI-I/O K diagnostics
features (refer section 5 of this manual). Initially the counter will need to be “zeroed” when the
shaft encoder is in the “zero level” position.
2.4.4
Pulse Rates
The rate of each pulse count is calculated and can be transmitted as internal analog inputs. The
rate is calculated on the increase of the base counter, not the rate of the input pulses. The
maximum count rate which can be calculated is 1000Hz. For PI1, this is the maximum pulse
rate that can be calculated. For PI2, a divider can be used for pulse rates more than 1KHz. The
pulse rate values can be scaled - that is, the user can configure what pulse rate (0.1 – 1000Hz)
corresponds to maximum analog value (20mA). Each pulse rate can be scaled individually.
Note that this is separate to the divider on PI2 count.
If the pulse inputs are configured for a shaft encoder, a pulse rate is still calculated -
corresponding to rate change of level. A zero rate (“steady level”) will correspond to a 50%
analog signal. The analog signal will be more than 50% if the level is increasing, and less than
