Rockwell Automation 1769-IR6 Compact I/O 1769-IR6 RTD/Resistance Input Module - Manual (Page 75)

Rockwell Automation Publication 1769-UM005B-EN-P - March 2012 75
Module Data, Status, and Channel Configuration Chapter 4
EXAMPLE Two Channels Enabled Using the Same Input Class with Cyclic Calibration Enabled
Channel 0 Input: 100
Ω Platinum 385, 1.0 mA source (Class 2) with 60 Hz filter
Channel 1 Input: 1000
Ω resistance, 0.5 mA source (Class 2) with 60 Hz filter
From Table 18, Channel Update Time versus Filter Frequency, on page 4-72:
1. Calculate Module Update Time without an Autocalibration Cycle
= Ch 0 Update Time + Ch 1 Update Time = 53 ms + 53 ms = 106 ms
2. Calculate Module Update Time during an Autocalibration Cycle
Channel 0 Step 1 (Module Scan 1)
= Ch 0 Update Time + Ch 1 Update Time + Ch 0 Offset Time = 53 ms + 53 ms + 73 ms = 179 ms
Channel 0 Step 2 (Module Scan 2)
= Ch 0 Update Time + Ch 1 Update Time + Ch 0 Gain Time = 53 ms + 53 ms + 106 ms = 212 ms
Channel 0, Step 3 (Module Scan 3)
= Ch 0 Update Time + Ch 1 Update Time + Ch 0 Gain Time = 53 ms + 53 ms + 73 ms = 179 ms
Channel 0, Step 4 (Module Scan 4)
= Ch 0 Update Time + Ch 1 Update Time + Ch 0 Gain Time = 53 ms + 53 ms + 73 ms = 179 ms
Channel 0 Step 5 (Module Scan 5)
= Ch 0 Update Time + Ch 1 Update Time + Ch 0 Gain Time = 53 ms + 53 ms + 106 ms = 212 ms
Channel 0 Step 6 (Module Scan 6)
= Ch 0 Update Time + Ch 1 Update Time + Ch 0 Gain Time = 53 ms + 53 ms + 73 ms = 179 ms
The above 6-step cycle could potentially take place for channel 1 as well. However, since channel 1 is the same
input class as channel 0, it uses the same calibration factors as channel 0, and no additional time is required.
At this point, the current source calibration cycle is run.
Current Source (Module Scan 7)
= Ch 0 Update Time + Ch 1 Update Time + Current Source Offset Time
= 53 ms + 53 ms + 73 ms = 179 ms
Current Source (Module Scan 8)
= Ch 0 Update Time + Ch 1 Update Time + Current Source Offset Time
= 53 ms + 53 ms + 106 ms = 212 ms
Current Source (Module Scan 9)
= Ch 0 Update Time + Ch 1 Update Time + Current Source Resistor Time
= 53 ms + 53 ms + 303 ms = 409 ms
3. Calculate Total Time to Complete Autocalibration Cycle
= (Channel Step Times) + (Current Source Times)
= (179 ms + 212 ms + 179 ms + 179 ms + 212 ms + 179 ms) + (179 ms + 212 ms + 409 ms)
= 1140 ms + 800 ms = 1940 ms = 1.940 seconds
After the above cycles are complete, the module returns to scans without autocalibration for approximately 5
minutes. At that time, the autocalibration cycle repeats.
If both cyclic autocalibration and lead wire compensation (see page 4-76) are enabled, the two functions run
concurrent to one another.