The COUT channel can have one of the following status values:
· Open load
· Start block
· Out of range
· Checksum error
· No contact (expansion modules)
The possible COUT statuses and triggering conditions varies some between the different modules; not all statuses are possible to have on all modules. There are more diagnostic methods than there are statuses on the list above, and there are even more possible wiring errors or other problems with the load that can trigger these diagnostic methods.
In the IQANdesign user manual, the section "Value and status" lists all statuses along with information on whether the status generates a dialog message and/or system log event. The status is also seen when measuring in IQANdesign/IQANrun.
The status when the function group or the expansion module the COUT is located on is disabled. It is a good design practice to disable optional functions to avoid triggering e.g. open load errors when an option is not fitted.
In the adjust menu, a disabled channel will appear with a padlock symbol and cannot be adjusted.
The normal status.
This is the status for faults indicating an open circuit in the wiring.
The XA2 and MC2 detects open load when the COUT is on, if the COUT is on and the resulting current is less than 50% of commanded the open load status is triggered.
MC3 and MC4x series can detect open load both when the COUT is on and when it is off, using several methods measuring both current and voltage on highside and lowside.
The MC3 Appendix A information specifies
-A load resistance as the open load threshold when the COUT is OFF
-The open/under threshold specified means that a resulting current more than 25% below commanded will trigger open load when the COUT is on.
MC4x Appendix B information specifies:
-External wiring faults, the state when these are detected and expected COUT status.
The overload status is used when the diagnostic method a fault that would causes a current higher than commanded.
The most intuitive cases are short to ground on high-side or low-side.
As with open load detection, the MC3 and MC4x series has methods for detecting overload both when the COUT is on and when it is off.
Connecting a load exceeding COUT maximum load may also trigger this error; a load with too low resistance can cause peak currents the COUT regulator cannot measure, in particular in combination with low inductance and low PWM frequency.
Commanding a current that is not possible to control could also result in this error status, for example commanding less than the specified 100 mA minimum current on and XA2 or MC2 may cause either open- or overload error detection to trigger.
When the commanded current is higher than what is physically possible to drive through the load with available supply voltage, the COUT status is saturated. This is a warning that the COUT is PWM:ing at full modulation ratio without achieving the commanded current.
This may be an indication that the application use coils with the wrong specification or that the COUT max current has been tuned too high, but it could also be an effect of temporary voltage drops, e.g. when cranking.
XA2, MC2 and MC4x can have the status saturated on COUT:s. The status saturated is only seen when measuring on the channel, it is not written to the log (since version 4.03)
This warning status is used to avoid unexpected startup after will occur after tuning of minimum current. If the COUT is still active when adjustment of minimum current is acknowledged, the COUT is set to this status and stops the output. The status is cleared by zero command to the COUT (e.g. releasing a joystick in case of manually activated outputs)
Related to start-block is the restart behavior after error statuses, here the COUT will remain in the error status until it is activated/deactivated to test again. It is possible to further restrict COUT restart with MC3/MC31 module properties in IQANdesign.
Out of range
All adjustable channels including COUT have limits set in IQANdesign. If the adjustable values would be outside of this range, the COUT status is set to out of range.
This status can be caused by sending an application where the limits are more narrow than what is currently adjusted in the settings.
All adjustable and stored channels including COUT have the setting individually checksum protected. If an error would cause corruption, this is detected by the check and the application falls back to using the application default values are instead.
Error, Critical Error
On MC3 and MC4x, diagnostics tests that are primarily designed to detect module internal faults will trigger the status Error or Critical error.
There are however a few application-related problems that can trigger the same diagnostic tests.
On MC3 (and MC31) applications with short cycle times, it is possible to give the COUT current regulator such rapidly varying commands that the error detection is triggered. The resulting status could be either open load, overload or error, depending on which diagnostic tests that triggers first The MC4x series is a much better choice for applications that need a short cycle time.
On MC4x and MC4xFS, it is possible to get the COUT status Error after a dip in supply voltage, this could occur in weak 12V systems.
All I/O on expansion modules are set to the status No contact if the master detects a module timeout. Expansion module traffic resumes automatically, but all activated outputs will remain in No contact as a form or start block function, until they are given a zero command.
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