Rockwell Automation 1746-NR8 SLC 500 RTD/Resistance Input Module User Manual - Manual (Page 52)

Publication 1746-UM003A-EN-P
4-4 Channel Configuration, Data, and Status
5. 5. 5. 5. Determine the desired input filter frequency for the channel and enter the
2-digit binary code in bit field 9 and 10 (Filter Frequency Selection) of the
channel configuration word. A lower filter frequency increases the channel
update time, but also increases the noise rejection and channel resolution. A
higher filter frequency decreases the channel update time, but also decreases
the noise rejection and channel resolution.
6. 6. 6. 6. Determine which channels are used in your program and enable them.
Place a one in bit 11 (channel Enable) if the channel is to be used. Place a
zero in bit 11 if the channel will not be used.
7. 7. 7. 7. Select the excitation current for the input channel. A zero in bit 12 provides
an excitation current of 1.0 mA; a 1 provides 0.25 mA. Select the excitation
current value based on RTD vendor recommendations and the Input
Specifications table, page A-2.
8. 8. 8. 8. Select the lead resistance measurement option. The module can disable lead
resistance measurement, periodically measure the lead resistance, or
measure the lead resistance on each acquisition for each one of the 8
channels. Setting a channel’s lead-resistance enable bits to 00 disables the
lead resistance measurement. Setting a channel’s lead resistance enable bits
01 enables the periodic measurement of the lead resistance, which occurs
once every 5 minutes. Setting a channel’s lead resistance enable bits to 10
enables measurement of the lead resistance on each acquisition cycle.
9. 9. 9. 9. Build the channel configuration word using the configuration worksheet on
page B-1 for every channel on each RTD module repeating the procedures
given in steps 1 through 9.
Enter the Configuration Data
Following the steps outlined in Chapter 5 (Ladder Programming Examples),
enter your configuration data into your ladder program and copy it to the
RTD module.