Quote:
Originally Posted by thingstodo
It turns out that 196K instead of 192K is workable - it's for STATUS anyway, which does not get to full scale. The scale of 0 - 98% works out to analog output of 220 - 4095
|
The PLC analog output is a '12 bit' digital to analog converter. You send a number to the analog channel and a proportional voltage is output from the terminals.
Most Allen-Bradley PLC 2, PLC 3 and PLc 5 analog cards are 12 bit. Some of the older ones are 8 bit. 12 bit means there are 4096 different voltages that can show up at the terminals. This corresponds to the numbers from 0 - 4095. If you show that in binary, there are 12 binary digits, or bits.
In the example above, 220 gives an output of 220/4095 * 10V or 0.53V. That puts a small current, about 2.7 micro amps, through the meter and the needle shows at 0 on the scale. No output on the analog shows below 0 on the scale.
So 4095, the high scale, puts out the full 10.01V available and still doesn't quite get to the 100% display value, labeled '200'.