Measurement Computing WaveView - Manual (Page 26)

WaveView, pg. 24 03-05-02 WaveView
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Falling Edge. The signal level must first go below the trigger level by the user-set hysteresis amount.
Then, the trigger channel is valid whenever the signal level is below the trigger level and stays valid
until the signal level goes above the trigger level by at least the hysteresis amount.
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Above Thresh. A trigger channel is valid whenever the signal level is above the trigger level and stays
valid until the signal level goes below the trigger level by at least the user-set hysteresis amount.
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Below Thresh. A trigger channel is valid whenever the signal level is below the trigger level and stays
valid until the signal level goes above the trigger level by at least the user-set hysteresis amount.
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Latch Rising Edge. The signal level must first go below the trigger level by the user-set hysteresis
amount. Then, the trigger channel is valid whenever the signal level is above the trigger level and stays
valid until the acquisition is complete.
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Latch Falling Edge. The signal level must first go below the trigger level by the user-set hysteresis
amount. Then, the trigger channel is valid whenever the signal level is below the trigger level and stays
valid until the acquisition is complete.
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Latch Above Thresh. A trigger channel is valid whenever the signal level is above the trigger level and
stays valid until the acquisition is complete.
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Latch Below Thresh. A trigger channel is valid whenever the signal level is below the trigger level and
stays valid until the acquisition is complete.
Note: The threshold voltage and hysteresis level may be set for each channel as required. Position the
cursor per channel and enter the desired value(s).
External Clock and Counter-Timer
WaveBook/512A, /516, and /516A can receive an external clock input through pin 20 of the DB25
connector labeled DIGITAL I/O, EXTERNAL CLOCK, TTL TRIGGER. This enables data scanning to be
correlated with an external pulse train. To enable the external clock, select “External” for the Scanning
Rate in the Acquisition Configuration Dialog Box (see following screen shot). When the external clock is
enabled, the WaveBook will begin a scan, only after a rising edge on the TTL level occurs. Optionally,
the external clock may be divided [by a factor of 1 to 255]. This “pre-scaling” allows the user to select a
reduced scan rate.
Note: The Clock Divider can be set
at a value from 1 to 255.
Acquisition Configuration Dialog Box with External Clock Enabled
WaveBook/516, /512A, and /516A each have a 32-bit internal counter that calculates and reports the
external clock’s period. The counter can be read with each scan of the analog data. This is often beneficial
in later analysis, when there is a need to correlate physical phenomena with speed.
The counter channel actually consists of two independent channels (CtrLo and CtrHi). These can be turned
“On” in the Channel Configuration Spreadsheet. When enabled, the low (CtrLo), then high (CtrHi) words
of the counter will be configured in each scan. Note that the spreadsheet’s Units column can be used to
view a predefined period in units of seconds, ms, or µsec.