JVL MIS17 Series User Manual page 29

2.3
Confidence alarms
If either of the Confidence Min or Confidence Max limits is used, it may be possible that
no new samples are accepted, which means that the filtered value will never change even
though there is a change in the input voltage. For instance, if the Confidence Min limit is
set to 2.0 V, and the actual input voltage is 1.50 V, the filtered value may continue to read
out 0.00 V (or the last value it had before exceeding the confidence limits).
To help troubleshooting in cases like this, each input has a status bit that is set if at least
half of the new samples during the last second lie outside either confidence limit. It is not
possible to see which of the confidence limits is violated. The status bits are updated once
per second.
Slope alarms
If the Max Slope limit is used (by setting its value lower than 4095), it may be possible
that many samples have their value limited. This is not necessarily an error in itself, but
can be a sign of a fault causing a noisy signal, or it can be a sign that the Max Slope limit is
set too low, which can have implications if the analogue voltage is used to control the mo-
tor speed, torque, etc.
To help troubleshooting in cases like this, each input has a status bit that is set if at least
half of the new samples during the last second were limited by the Max Slope setting. The
status bits are updated once per second.
Example of analogue input filter operation:
Note that even though the examples use units rather than Volts, decimal values are used,
since the motor uses a much higher resolution internally to store the units.
Also note that as long as the slope limitation is in effect, the result will keep a constant
slope even when using a filter. When the slope limitation is no longer in effect, the filter
will cause the value to approach the final result more slowly as it approaches the result.
Confidence Min = 0, Confidence Max = 500, Max Slope = 10, Filter = 8, Old filtered
value = 0.
Sample 1 = 100
Sample 2 = 100
Sample 3 = 100
Sample 4 = 800
Sample 78 = 100
Sample 79 = 100
Sample 80 = 100
Sample 81 = 100
JVL Industri Elektronik A/S - User Manual - Integrated Stepper Motors MIS17x, 23x, 34x, 43x
Analogue Inputs
Confidence OK, slope limit to 0 + 10 = 10,
result = 10*(8/64)+0*(56/64) = 1.25 units.
Confidence OK, slope limit to 1.25 + 10 = 11.25,
result = 11.25*(8/64)+1.25*(56/64) = 2.5 units.
Confidence OK, slope limit to 2.5 + 10 = 12.5,
result = 12.5*(8/64)+2.5*(56/64) = 3.75 units.
Confidence error, keep old value, result = 3.75 units.
...and so on until the result gets ~= 95.0 units...
Confidence OK, no slope limitation needed,
result = 100*(8/64)+95*(56/64) = 95.625 units.
Confidence OK, no slope limitation needed,
result = 100*(8/64)+95.625*(56/64) ~= 96.171875 units.
Confidence OK, no slope limitation needed,
result = 100*(8/64)+96.171875*(56/64) ~= 96.65 units.
Confidence OK, no slope limitation needed,
result = 100*(8/64)+96.65*(56/64) ~= 97.07 units.
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