Digital Trigger (MRI Trigger)
Use the DTU100 Digital Trigger Unit to trigger an MRI System with the occurrence of the R-wave present in
animal (high frequency) ECG data. The DTU100 provides high-level (3000 V) isolation between the MP System
and external equipment; the DTU100 is always used with the HLT100C module. This isolation is very important
to maintain both subject safety and high quality signal recording. This external hardware module can accept data
from any analog output associated with an MP System and convert that analog signal into a TTL compatible
trigger suitable for synchronizing with external devices.
For the DTU100, “Analog output” means:
1) Analog output associated with any MP module (DA100C, ECG100C, etc) that is sending data to an MP
System on Analog Input channels 1–16.
2) Analog output coming from the MP system via one of its D/A converters on Analog Output channel 0–1.
To synchronize an MRI System with the occurrence of the R-wave, record animal (high frequency) ECG data on
an ECG100C amplifier and direct the output to an analog input channel on the MP100/150 Unit.
a) Connect the DTU100 RJ11 cable to the HLT100C channel that is sourcing the ECG analog signal. For
example, if acquiring ECG waveform on Channel 2, connect DTU100 RJ11 to channel 2 on the HLT100C.
b) Use CBL100 cables to connect the Threshold, Trigger and/or Signal View to unused analog channel inputs on
the UIM100C to monitor signals in AcqKnowledge.
c) Connect the Trigger Out (TTL) line to the MRI system requiring synchronization to the R-wave of the ECG.
d) If the R-Wave is a clearly defined peak, run the DTU100 in Normal mode. If the R-wave is not always
predominant, consider operating the DTU100 in Auto Level mode, or change the location of ECG leads on the
subject to obtain a better-defined R-wave peak.
e) Adjust the Trigger Level potentiometer to obtain a Trigger Signal. Change the Trigger Out polarity to Positive
or Negative as required for the MRI equipment. Verify proper operation by noting the periodic lighting of the
green Trigger LED. This LED should light briefly whenever the R-wave is detected.
BIOPAC Hardware | DTU100 | Page 1 - 2
Updated: 8.29.2014
Feedback Views
The DTU100 is always used with the HLT100C module. Use the RJ-11 straight
through cable provided by BIOPAC to plug the DTU100 into the HLT100C.
The DTU100 incorporates three feedback outputs that can be monitored on the MP
System to properly set the threshold (trigger) level and required Trigger Out polarity
for any type of analog input. Use a 3.5 mm mono phono cable (CBL100) to connect the
respective line to an unused MP system input channel.
Threshold View Shows the Threshold (Trigger) Level
Trigger View Shows the Trigger Output as sent to the external equipment.
Signal View Shows the analog input signal as sent to the DTU100.
Trigger Out
Connect a TTL line with BNC female connector between the DTU100 and the trigger
Normal/Auto Level The DTU100 incorporates an optional Automatic Level control circuit. The Automatic
Level control circuit will expand or compress the analog input signal to fit inside of a
±5 V range.
Normal — use if the analog input signal is clearly defined.
Auto Level — use if the analog input signal has a widely varying baseline or
significant change in amplitude from one desired trigger point to the next; or to try
to improve signal definition.
The Trigger LED (green) lights up whenever the Trigger Out signal goes high.
If analog data is above the threshold setting the DTU100 output can be set to either
high (+5 V) or low (0.0 V). When analog data drops below the threshold value the
output will be the opposite level.
Trigger Level
Select a trigger level (or threshold) that will fire when analog data reaches that
See also: DTU200/300 Systems
BIOPAC Hardware | DTU100 | Page 2 - 2
Updated: 8.29.2014
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