Rockwell Automation 1771-IR Series D RTD Input Module User Manual - Manual (Page 70)

Differences Between Series A RTD Modules and Series B. C and D RTD Input Modules F–2
Publication 1771Ć6.5.129 - March 2000
•
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.
•
If the module is programmed for RTS = 0 and the PLC is
switched from run to program and back to run, an RTS timeout is
inhibited on the change from program to run.
•
In ohms mode, bias is able to produce a negative result.