Measurement Computing PCI-2511 User Manual page 26

PCI-2511 User's Guide
Detection on an analog input, timer output updates
Update Mode: Update on True and False
Criteria Used: Inside window
The figure below shows how a setpoint can be used to update a timer output. Channel 3 is an analog input
channel. A setpoint is applied using update on True and False, with a criteria of inside-the-window, where the
signal value is inside the window when simultaneously less than Limit A but greater than Limit B.
Whenever the channel 3 analog input voltage is inside the setpoint window (condition True), Timer0 is updated
with one value; and whenever the channel 3 analog input voltage is outside the setpoint window (condition
False) timer0 will be updated with a second output value.
Using the hysteresis function
Update mode: N/A, the hysteresis option has a forced update built into the function
Criteria used: Window criteria for above and below the set limits
The figure below shows analog input Channel 3 with a setpoint which defines two 16-bit limits, Limit A (High)
and Limit B (Low). These are being applied in the hysteresis mode and FIRSTPORTC is updated accordingly.
In this example, Channel 3's analog input voltage is being used to update FIRSTPORTC as follows:
When outside the window, low (below limit B) FIRSTPORTC is updated with 30 h. This update remains in

effect until the analog input voltage goes above Limit A.
When outside the window, high (above limit A), FIRSTPORTC is updated with 30 h. This update remains

in effect until the analog input signal falls below limit B. At that time we are again outside the limit "low"
and the update process repeats itself.
Hysteresis mode can also be done with a timer output, instead of a FIRSTPORTC digital output port.
Figure 19. Timer output update on True and False
Figure 20. Channel 3 in hysteresis mode
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Functional Details