Signal Connections Chapter 3
PC-OPDIO-16 User Manual 3-4 © National Instruments Corporation
Optically Isolated Digital Output
I/O connector pins 1 through 24 shown in Figure 3-1 represent the optically isolated output
signal pins.
Output Channels
The optically isolated outputs of the PC-OPDIO-16 consist of a photo coupler and a load resistor.
The PC-OPDIO-16 has eight isolated output channels. Each channel has its own isolated ground
(COM), supply (VCCO), and output signal (VOUT). Figure 3-2 shows signal connection
examples for isolated output.
The maximum power ratings for the PC-OPDIO-16 are as follows:
• Maximum supply voltage (VCCO), 24 VDC
• Maximum output high current (I
OH
) = 250 µA
(VOUT = 3 V when VCCO = 5 V, or at VOUT = 22 V when VCCO = 24 V)
(shown in Figure 3-2a)
• Maximum output low current (I
OL
) = 7.0 mA at supply = 5 to 24 V (shown in Figure 3-2b)
Note: The data rate at the output is limited by the hardware. The maximum data rate
achievable with the PC-OPDIO-16 is 5 kHz. But the data rate may be slower than
5 kHz, depending on your software and CPU speed.
Signal Isolation
The COM, VCCO and VOUT signals of each channel are isolated from outputs of other channels
and also isolated from the PC-OPDIO-16 internal power and ground signals. These barriers
provide an isolation for voltages upto +24 VDC and protect the PC-OPDIO-16. Common-mode
voltages higher than the +24 VDC may damage your equipment.
Warning: You must not exceed the voltage limit of the VCCO referenced to their respective
COM signals. National Instruments is
NOT liable for any damages resulting from
signal connections that exceed these limits.
