Omega OMB-DAQBOARD-3000 Series User Manual page 73

The setting of a detection window must be done with a scan period in mind. This applies to analog inputs
and counter inputs. Quickly changing analog input voltages can step over a setpoint window if not
sampled often enough.
There are three possible solutions for overcoming this problem:
(1)
(2)
(3)
Example: Setpoint Detection on a Counter in Encoder Mode.
The figure above shows values pertaining to a Counter in Encoder Mode. The acquisition is started
and 16-bit data [from the counter] streams into the PC at the scan rate. The 16-bit counter data is
interpreted as the position from an encoder, which is connected to the counter inputs.
The update on True and False mode is being used. Thus, one value is output on P2C when the
position is outside of the window (a value of 10h in the example); and a second value is output on P2C
when the position is inside the window (a value of 20h in the example).
In the True and False mode, each setpoint has two DAC update values, two P2C update values, or 2
timer update values. One of the two values is used to update the DACs, P2C, or timers when it is true
that the input channel meets the setpoint criteria. The second value is used to update the DACs, P2C,
or timers when the condition is false, i.e., when the setpoint criteria is not met.
DaqBoard/3000 Series User's Manual
The scan period could be shortened to give more timing resolution on the counter values or
analog values
The setpoint window can be widened by increasing Limit A and/or lowering Limit B.
A combination of both solutions (1 and 2) could be made.
Limit A
Limit B
Encoder
Position
P2C
Example of a Counter in Encoder Mode
By software default, P2C comes up as a digital input. If you want the P2C signal
to be a digital output [in some initial state before an acquisition is started] and
P2C is to be updated by set point criterion, then you must do an asynchronous
write to P2C before the acquisition is started. The initial value will only be output
if the asynchronous write to P2C has been performed.
908794
Setpoint Configuration for Output Control 6-5