Trigger Input; Counter Input; Vo Power Source - Measurement Computing USB-234 User Manual

USB-234 User's Guide

Trigger input

The TRIG terminal is an external digital trigger input. The trigger mode is software-selectable for rising edge- or
falling edge detection.

Counter input

The terminal is a 32-bit counter that can count rising edges. Edges can only be counted up from 0.
CTR
Counting down is not supported – you cannot set the initial count to 100 and count down to 99, 98, 97.

+VO power source

Figure 11 shows the +VO
The main blocks featured in the

+5 V Source —Regulated 5 V supply.

—Circuit for overvoltage, over current, and short circuit protection.
+5 V Protection
The +5 V source is limited at 200 mA typically. In case of hard short circuit to ground, this limit is further
reduced to avoid excessive power dissipation.
Connecting the load
The return terminal for the +5 V source is the
+VO terminal and GND
connector. To meet the USB specifications, a maximum of 150 mA can be used from the
power source circuitry of the USB-234.
Figure 11. +VO power source circuitry
power source circuitry are as follows:
+VO
GND
. The current delivered by the USB-234 at the
terminal. The +5 V load should be connected between the
+VO terminal is sourced from the USB
19
Functional Details
terminal.
+VO