Allen-Bradley MicroLogix 1200 User Manual page 63

Two Channels Enabled with Cyclic Calibration
EXAMPLE
Channel 0 Input: 100Ω Platinum 385, 1.0 mA source with 60 Hz Filter
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Channel 1 Input: 100Ω Platinum 385, 0.5 mA source with 60 Hz Filter
From Table 3.15, Channel Update Time vs. Filter Frequency, on page 3-27:
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 + RTD ADC Self-calibration Time = 53 ms + 53 ms + 103 ms = 209 ms
Channel 0 Step 2 (Module Scan 2)
= Ch 0 Update Time + Ch 1 Update Time + Current ADC Self-calibration Time = 53 ms + 53 ms + 103 ms
= 209 ms
Channel 0, Step 3 (Module Scan 3)
= Ch 0 Update Time + Ch 1 Update Time + Current Source Calibration Time = 53 ms + 53 ms + 53 ms = 159 ms
Channel 0, Step 4 (Module Scan 4)
= Ch 0 Update Time + Ch 1 Update Time + Ch 0 Lead Compensation ADC Calibration Time
= 53 ms + 53 ms + 130 ms = 236 ms
Channel 1, Step 1 (Module Scan 5)
= Ch 0 Update Time + Ch 1 Update Time + Ch 1 RTD ADC Self-calibration Time
= 53 ms + 53 ms + 103 ms = 209 ms
Channel 1, Step 2 (Module Scan 6)
= Ch 0 Update Time + Ch 1 Update Time + Ch 1 Current ADC Self-calibration Time
= 53 ms + 53 ms + 103 ms = 209 ms
Channel 1, Step 3 (Module Scan 7)
= Ch 0 Update Time + Ch 1 Update Time + Ch 1 ADC Self-calibration Time
= 53 ms + 53 ms + 53 ms = 159 ms
Channel 1, Step 4 (Module Scan 8)
= Ch 0 Update Time + Ch 1 Update Time + Ch 1 Lead Compensation ADC Calibration Time
= 53 ms + 53 ms + 130 ms = 236 ms
3. Calculate Total Time to Complete Autocalibration Cycle
= (Channel 0 Step Times) + (Channel 1 Step Times)
= (209 ms + 209 ms + 159 ms + 236 ms) + (209 ms + 209 ms + 159 ms + 236 ms)
= 786 ms + 786 ms = 1626 ms = 1.626 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 3-30) are enabled, the two functions run concurrent to one
another.
Calculating Module Update Time with Autocalibration Enabled
The following example illustrates how to determine module update
time with autocalibration enabled.
Module Data, Status, and Channel Configuration
Publication 1762-UM003A-EN-P - February 2003
3-29