National Instruments OAC5 用户手册

©

 National Instruments Corporation

3

The dropout voltage and current specifications for the output modules are 
given in the 

 section. For most control 

applications, such as controlling motors or lamps, these requirements are 
not difficult to meet.

A second difference between these output modules and conventional relays 
is that they do not turn off completely. A small leakage current flows all the 
time even in the off state. For most control applications, this current causes 
no problems.

Output SSR modules require a certain amount of current from the digital 
control for the module to turn on. If the DAQ device sends a logic high 
signal, the output module turns off and no current flows. If the DAQ device 
sends a logic low signal, the output module turns on and current flows from 
the +DC control or V

cc

 to the -DC control. This current must be large 

enough to turn on the output module. If the DAQ device or digital control 
cannot sink enough current through the -DC control, the module does not 
turn on. Refer to Table 1 to find the minimum logic control current required 
to turn on each output module.

This section describes the SSR backplane in detail including connection, 
function, SSR module installation, and field connections.

All four SSR backplanes function similarly, but they accommodate a 
different number of modules. Each backplane has a special cabling scheme 
to maximize the number of modules in use.

Table 1.  Minimum Control Logic Current Required 

ODC5

5 mA

OAC5

12 mA

OAC5A

12 mA