3.9 Signal Connection
The analog outputs of the CIO-DAC## are two-wire hookups. A signal, labeled
D/A # OUT on the connector diagram below, and a Low Level Ground (LLGND).
The low level ground is an analog ground and is the ground reference which should
be used for all analog hookups.
Possible analog output ranges are:
0 to 2.5V0 to 5V0 to 10VUnipolar Ranges and +2.5V+5V+10VBipolar Ranges
See the range select switch in section 3.5.
Each of the DAC## outputs are individually buffered through an OP07 operational
amplifier (OP-AMP). The OP07s are socketted so that if one fails it can be replaced
in the field. The OP07 for each channel is located just below the calibration
potentiometers for that channel.
At the full rated output swing of ±10V, each channel is capable of sinking or
sourcing ±5 mA. That means a load of 2K Ohms can be connected to each channel.
As the load resistance is raised from 2K up to 10 Megaohms or more, the output
load on the DAC decreases. Any load resistance greater than 2K is fine.
As the load resistance decreases, the output load increases. The OP07 responds by
producing a lower output voltage. If your CIO-DAC## will not produce the output
voltage specified by the code & range combination, it is a good idea to check the
load with an ohm meter.
Under normal circumstances you will not damage the OP07 by connecting the
output to ground. If your connection results in a failure of the OP07, chances are
good that there was some potential at the connecting point in addition to a load at
ground or between 0 and 2K ohms. Explore the point with a DVM before
reconnecting the CIO-DAC## (and after replacing the OP07 of course). Connect
the negative lead of the DVM to any LLGND pin of the CIO-DAC##.
7