Figure 2-1. Trigger input equivalent circuit.
2.1.2 External Hardware Trigger Output
Output Characteristics
Output Circuit
Open collector of a NPN transistor (nominal 0.4V saturation voltage) in series with 1k
resistor.
Collector Emiter Voltage
< 30 V
Output Current
< 4 mA
Reverse Voltage
< 7V
Isolation
Optically Isolated from all other circuitry. Common line with Trigger Input.
Figure 2-2. Trigger Output Optical Isolator NPN circuit.
2.1.3 Using the PXI bus Trigger Facilities
The SMX4030 series of Switching modules are designed to interface to the PXI bus Triggers. That includes the
PXI_TRIG1 through PXI_TRIG6 and PXI_STAR trigger. The trigger is a Wire-Ored function of the external
trigger at the DB-78 connector, or the PXI_TRIGn input. The trigger output of the Scanner can be set to drive
PXI_TRIG1 through PXI_TRIG6 or PXI_STAR trigger. To use the Trigger input and output lines of the DB-78
connector, set both the PXI Trigger Output select and PXI Trigger Input select switches to 0 (all switches in the off
position).
Figure
4-8.
PXI Trigger input/output selection switchs.
2.1.3.1 PXI Trigger Outputs
The DMM issues a Data Ready pulse each time the A/D is done making a measurement, indicating data
is ready to be read. A short (about 140
s) negative pulse is issued for each measurement, with the
9
Signametrics
