User manual

905K Radio Telemetry Module User Manual
 ELPRO Technologies Pty Ltd 2010 Page 14
• 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 905K 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 905K 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 905K 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
50% if the level is decreasing. If an incremental shaft encoder is used, then the rate may be
scaled by scaling PRATE1. If a quadrature encoder is used, scale PRATE2. The scaling value
will determine both the 100% analog signal (e.g. 20mA) and 0% signal (e.g. 4mA). For
example, if a maximum pulse rate of 10Hz is configured, then the analog signal will be:
100% if the encoder increases at 10Hz 50% if the encoder pulse rate is 0
0% if the encoder decreases at 10Hz. 75% if the encoder increases at 5Hz
25% if the encoder decreases at 5Hz
Note that this is only true if the pulse inputs are configured for a shaft encoder. If standard pulse
inputs are used, then 0% analog signal will correspond to zero pulse rate (0Hz).
The pulse rates are treated as analog inputs and follow the rules for an analog input as described