Spectrum Controls Micro850 User Manual page 36

3-14 Chapter 3: Configuring the 2085sc-IF16 Using CCW
User's Manual Pub. 0300306-01 Rev. A
 If the Process Alarm Latch bit is enabled, then clear the appropriate
alarm status bit when both of the following conditions are satisfied:
-
The channel input value is no longer within the alarm value
range, and
-
The Set Latch Clear bit in the output table is set.
This bit must remain set until the appropriate Alarm Status bit is
NOTE
cleared. This bit can then be cleared again. The module does not
latch an alarm condition if a transition from no alarm to alarm
occurs while a channel's Set Latch Clear bit is set.
Open Circuit Detection
The open circuit detection feature alerts you to an open circuit condition by
setting the open circuit status bit and displaying a high limit, low limit, or zero
data value for the appropriate channel(s) in the input table.
Open circuit detection may also be disabled for any or all channels:
Open Circuit
Index
Detection
0 Upscale
1 Downscale
2 Zero
3 Disable
The open circuit detection behavior depends on the channel input range selection
and the open circuit detection selection bits for each channel:
 For voltage range selections (IF16V only):
-
Open circuit detection takes place on a periodic basis, every 3
seconds, by temporarily enabling the PGA burnout current, and
initiating an ADC conversion at the fastest filter frequency (470
Hz).
-
The previous measurement remains in the input table during the
open circuit detection procedure (that is, the measurement value
with the burnout current enabled is not reported).
-
Within 3 seconds of an open circuit condition, transitional data
may be reported prior to the open circuit status bit being set.
 For the Upscale open circuit detection setting, an open circuit condition
causes the channel input data to report the high limit data value for the
selected input range and data format and the open circuit status bit is set.
As a side effect of this, the over range status bit is also set.
 For the Downscale open circuit detection setting, an open circuit
condition causes the channel input data to report the low limit data value
for the selected input range, and data format and the open circuit status
bit is set. As a side effect of this, the under range status bit is also set.
 For the Zero open circuit detection setting, an open circuit condition
causes the channel input data to report a value equivalent to zero for the
selected input range, and data format and the open circuit status bit is set.
Note
Default