Rockwell Automation 1771-IR , D17716.5.76 RTD INPUT MODULE - Manual (Page 64)

Differences between Series A
and Series B
Appendix F
FĆ2
When displaying copper (10mohm/bit resolution) in ohms, the resistance
will be provided up to 327.67 ohms at which point an overrange will occur
(overrange on the Series A was 20.72 ohms). Platinum (30mohm/bit
resolution) will over range at 600.00 ohms but continue to measure until the
input saturates (Series A was 399.99 ohms). Underrange for the Series B
will be 1 ohm but continue to display until the input can no longer track. The
Series A underranged at copper – 1.17 ohms; platinum – 18.39 ohms. The
Series B continues to track beyond the under or overrange, except
overrange on copper which clamps at 327.67 ohms. The Series A clamped
the reading at the under or overrange value.
Open RTD detection (excitation signal disconnected) will flag an Overrange
instead of Underrange.
Open RTD detection is < 0.5 seconds.
Overrange will continue to function as a flag, even if single channel ohms
has been requested.
When a channel is displaying temperature and an overrange is detected,
BTR temperature data for that channel will be clamped at the RTD
maximum temperature (Platinum – 870
o C or 598 o F with Overflow, if
customer bias has not been applied; Copper – 260 o C or 500 o F).
A block transfer with a word length of 00 will return with the Series A
block transfer default length (14 for a write; 8 for a read). To access the
auto–calibration word, the block transfer length must be set to 15 for a write
and 9 for a read.
Auto–calibration can be performed on all channels simultaneously or on
selected channels. In either case, channels being calibrated must be
connected to the precision calibration resistors.
The Series B module requires approximately 2 seconds to power up.
The red LED is illuminated and the green LED is extinguished if the
watchdog timer times out.
This module employs a digital filter with 120dB/decade rolloff from a
corner frequency of 8 Hz.
This Series B module is NOT compatible with the 1771–EX extender
board. Use the 1771–EZ extender board with Series B.
Platinum RTD tables are based on IEC751 alpha = .00385. The 1771–IR/A
was based on MINCO Products, Inc measurements of IEC751 RTDs.