External Digital (Ttl) Trigger - Measurement Computing Data Translation DT3034 User Manual

Chapter 6

External Digital (TTL) Trigger

For analog input operations, an external digital trigger event occurs when the DT3034 board
detects either a rising or falling edge on the External A/D TTL Trigger input signal connected
to screw terminal 77 on the DT740 screw terminal panel. The trigger signal is TTL-compatible.
Using software, specify the trigger source as an external, positive digital (TTL) trigger for a
rising-edge digital trigger (OL_TRG_EXTERN for DataAcq SDK users) or an external,
negative digital (TTL) trigger for a falling-edge digital trigger (OL_TRG_EXTRA for DataAcq
SDK users).
Analog Threshold Trigger
For analog input operations, an analog trigger event occurs when the DT3034 detects a
transition from above a threshold level to below a threshold level (falling edge), or a transition
from below a threshold level to above a threshold level (rising edge). The following analog
threshold trigger sources are available:
• External Analog Trigger input signal – This trigger source is supported by the DataAcq
• One of the analog input channels after gain is applied (also called the output of the
On DT3034 boards, the threshold level is set using a dedicated 8-bit DAC (the second D/A
subsystem). The hysteresis is fixed at 50 mV. Using software, program the threshold level by
writing a voltage value to this DAC; this value can range from –10 V to +10 V.
Note: If you are using an analog threshold trigger to trigger both the A/D and the D/A
subsystems, ensure that you use the same analog trigger type for both subsystems (either
external or one of the analog input channels). The polarity of the triggers, however, can be
different.
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SDK; it is not supported by the DT-Open Layers Class Library.
Connect an external analog trigger signal to screw terminal 107 on the DT740 screw
terminal panel.
Using software, specify the trigger source as either a rising-edge (OL_TRG_EXTRA+1 for
DataAcq SDK users) or falling-edge analog threshold trigger (OL_TRG_EXTRA+2 for
DataAcq SDK users).
programmable gain amplifier (PGA). Using software, specify the trigger source as either a
positive threshold trigger or negative threshold trigger.
Using software, specify the analog input channel used as the analog threshold trigger as
the first channel in the channel list; refer to page 72 for more information.