Logic For DO & DI ,AI & AO

digital output means 24 volt out when DCS or PLC send command you get 24v & run through DO card to your relay solenoid but it's in black & white wire 24 volts ok, no dry contact ......( i mean used black & white as dry there is no polarity as + & - , only +) cause minus (-) already at card , cause plus contact will through all field to sensor and comeback at card...

any confusion

if you used 24 volt +& - from digital card to field relay or push button & when it's energized or contact close that time your wired plus & minus are getting short circuit..it cause i alrady measure 24 volt across terminal when stop command from DCS for motor , where 0 volt across start command , actual motor is off not running ...when command comes from dcs start shows 24 & stop shows "0" ? so what about dry contact?

Read the manual(s) for your equipment. They'll almost certainly include examples of how to connect various types of input and output.

can suggest good documents available at on any site ?

What make and model(s) of equipment?

JohnDG is right. You need to submit the make and model of the PLC, or have you finally delved into the instructions and now feel foolish for not doing so from the outset?

RTFM.

Anonymous,

The word "circuit" is chosen because it means that there is a complete path from the power source through the controlling device to the load and finally returning to the power source. This is true for AC, or DC. For DC devices, the polarity will be very important whenever you are using transistors.

For a digital/discrete input device, the "load" is the digital/discrete input and the "controlling device" is a switch, or other sensor. Some of these sensors require their own source of power to run (so they would require three or even four wires), while others may draw their operating power as a small "parasitic" load on the two-wire loop to them.

For a digital/discrete output device, the "controlling device" is the digital/discrete output and the "load" is a relay, solenoid, light, motor starter coil, etc.

If you check the wiring diagram for your controller, you will see one or more terminals labeled as "common", with the label telling which inputs or outputs it is associated with. If you fail to make a connection from this common terminal to the appropriate power supply terminal, your controller may appear to have no faults, but there will be no control of your machine.

OK?--JMM