Rockwell Automation 61C544A RTD Module - Manual (Page 24)

4Ć8
another configuration command. If you try to enter another
configuration command before bit 15 of register 22 is reset, error bits
7 and 14 in register 22 will be set.
4.1.9 Channel Number Register (Register 23)
Register 23 contains the number of the channel to be configured,
read, or reset. Channel numbers can range from 0 to 15. A channel
number outside of this range will be flagged as an error.
4.1.10 Number of Samples Register (Register 26)
Register 26 specifies the number of input data samples that will be
averaged together. The module maintains a running average of x"
number of input data samples. The value in the register is a 15Ćbit
plus a signĆbit integer. The default value is one. The maximum
allowable value is 60.
If the register contains a value of zero or one, no input data will be
averaged together. If the register contains a negative number, a
configuration error will result.
As the number of input samples increases, the time span of
averaging increases, which results in a less current input value for
use in the application program. See figure 4.9 for an equation to
determine the amount of time needed to calculate an average input
value for registers 0 to 15.
Where:
# of configured channels = 0 to 16
cycle frequency time =
20 msec for 50 Hz
16.6 msec for 60 Hz
system overhead = 5 msec
# of samples = 1 to 60
averaged time = time in seconds
= time the value in
reg. 0Ć15 was
averaged over
# of
configured
channels
cycle
frequency
time
system
overhead
# of
samples * + *
Figure 4.9 Ć Equation for Determining the Input Value Averaging Time
4.1.11 High High Alarm Register (Register 27)
Register 27 defines the High High alarm limit. If a channel's input
value exceeds this limit, the channel's corresponding bit in register 16
is set to one. The value in register 27 is a 15Ćbit plus a signĆbit integer.
This value is in units of 0.1 degrees.
If register 27 does not contain the largest alarm value, a configuration
error will result. At powerĆup, the register is set to a default value of
4000 (4000 x 0.1_C = 400_C).