Xylem XL Series H-522 - Plus - Manual (Page 109)

XL™ Series
Digital I/O 12-7
12.4 Quadrature Shaft Encoder Options
The XL™ uses the two digital I/O pins to connect to a quadrature shaft encoder or to simulate a
quadrature shaft encoder. For proper operation with a shaft encoder that increments clockwise,
the phase A signal should be input into pin 1 and the phase B signal should be input into pin 2.
NOTE: When the digital I/O are used for shaft encoder input they cannot be used as outputs.
PC Interface View Built In Display Screen
O - Encoder Out Source: None Enc Out Src [None ]
The two digital I/O pins can be used together to output a quadrature signal. The source for this
output mode would be any of the standard input variables such as stage or analog channel 1. The
most common is the stage variable on the H-350 XL or another input source like an SDI-12 input
that is used to read the stage. However any data source could be used. If this option is set to
NONE then the encoder output options is disabled. With this set to none the digital I/Os can be
used for normal digital I/O operations or as a shaft encoder input.
Scanning should be turned off when enabling this option. When this mode is enabled and
scanning is turned on the system will measure a reference or starting point. Each time the unit
scans it will measure the selected source and compare the new value with the older reference
value and toggle the digital I/O’s based on the difference. Then the new value is saved as the
reference point to be used with the next scan.
PC Interface View Built In Display Screen
V - Encoder Value Encodr val[X.XXX ]
When both of the digital I/O pins are configured as inputs, they may be used to read a quadrature
shaft encoder. The current value of the shaft encoder will be displayed here. This value may also
be edited by the user in order to set the value to some reference point. The internal counter can
count ±32767 counts. When a new value is entered, the internal counter is reset allowing the
counter to count ±32767 counts from the new value, not from zero.