Sigma C4 manual Noise Immunity

train your users to use their finger to discharge the static potential they may have accumulated on something other than the C4 front panel.

9.7.4 Noise Immunity

Noise can show up as lost or incorrect data sent over the bus. In extreme cases this noise can disrupt controller operation regardless of whether computer bus is in control or not. The following modification has been found to solve many computer bus related noise problems. It will provide static ground to the backshell of the IEEE 488 bus connector as well as pin 1 of the EIA-232 connector, bypassing any path through the digital circuitry. It is not done at the factory because in some cases it actually degrades noise immunity by creating a ground loop.

Bus static ground connection is made as follows: Solder a short green 22g. wire to the A-Board static ground eyelet located below the IEEE-488 connector. Hook the other end of the wire to a horseshoe lug and connect it to the main terminal strip J1, lug #3. (green).

9.7.5 Diagnosing and Solving Local Mode Problems

Controller starts immediately in Local Mode

If the system improperly begins controlling to the setpoint when you turn the controller from OFF to LOCAL Mode, before you press <START/STOP>, the Autostart setup parameter (F14) is set to enable Autostart. Resetting this setup parameter to 0 will disable the automatic starting feature.

9.7.6 Diagnosing and Solving Program Mode Problems

Hard Loops

Also note that hard loops will execute forever. Standard loops, using the loop command, do not allow nesting. Only one loop may be active at a time. If you have a nested loop, it may appear to function properly, but it will probably never complete.

104 C4 Manual Rev 7.5.2