National Instruments NI-FBUS - Manual (Page 113)

Appendix B Troubleshooting and Common Questions
NI-FBUS Configurator User Manual B-4 ni.com
Why are discrete states integers instead of booleans?
Because it allows for multiple state discrete functionality such as off,
turning on, on, and turning off. Not all devices take full advantage of this.
For example, on the FP-3000, 0 is off, and 1–16 are on. Because these
parameter values are integers, they show up in your HMI as analog.
Bad Status
You receive a status of Bad:Device Failure .
An error exists with the hardware. Set the RESTART parameter in the
block configuration window to Processor or Default . If the problem
persists, replace the device.
PID block shows bad quality.
• The function block is not actually executing on the device. Make sure
you placed it in the Function Block Application Editor window and
downloaded the project.
• The PID is not subscribing correctly. Go to the schedule and pull the
blocks apart a bit to allow more time. Make sure that there is sufficient
unscheduled time left in the schedule. Download the project after
changing the scheduler or Function Block Application Editor.
• If this still does not solve the problem and your configuration file
contains the entire application, download with the Clear Devices box
checked.
I am using a PID loop to control a 4-20 mA signal. The range for my
analog input block is 4-20 mA. The quality of the reading of my PID
block is Uncertain when it reaches the setpoint (20 mA). Why?
The value the analog input is reading when the PID reaches the setpoint is
20 mA. The device reports the quality as Uncertain because the device is
able to read inputs only up to 20 mA. If you actually have an input of
21 mA, the device will read this as 20 mA, since this is the maximum range
setting. If the input is 20 mA, the device will read this also as 20 mA.
For this reason, it is impossible to know whether a reading of 20 mA is
actually a good reading or not. The device reports Uncertain status so that
the user is aware that signal value might not really be 20 mA. To make sure
that you get a quality of Good, you simply increase the range to something
slightly larger than your maximum expected value. You also can force the
NI-FBUS Configurator to treat Uncertain as Good. This is done on a
function block-by-function block basis. Double-click the block for which