Campbell Scientific CR9000X Measurement and Control System - Manual (Page 53)

Overview
OV2.2 Measurements, Processing, Data Storage
The CR9000X divides a program into two tasks. The measurement task
manipulates the measurement and control hardware on a rigidly timed
sequence. The processing task processes and stores the resulting
measurements and makes the decisions to actuate controls.
The measurement task stores raw Analog to Digital Converter (ADC) data
directly into memory. As soon as the data from a scan is in memory, the
processing task starts. There are at least two Scan buffers allocated for this
raw ADC data (additional buffers can be allocated under program control),
thus the buffer from one scan can be processed while the measurement task is
filling another.
When a program is compiled, the measurement tasks are separated from the
processing tasks. When the program runs, the measurement tasks are
performed at a precise rate, ensuring that the measurement timing is exact and
invariant.
Processing Task: Measurement Task:
OV2.3 Data Tables
The CR9000X can store individual measurements or it may use its extensive
processing capabilities to calculate averages, maxima, minima, histograms,
FFTs, etc., on periodic or conditional intervals. Data are stored in tables such
as listed in Table OV2-1. The values to output are selected when running the
program generator or when writing a datalogger program directly.
Table OV2-1. Typical Data Table
TOA4 StnName Temp
TIMESTAMP RECORD RefTemp_Avg TC_Avg(1) TC_Avg(2) TC_Avg(3) TC_Avg(4) TC_Avg(5) TC_Avg(6)
TS RN DegC DegC DegC degC degC degC degC
Avg Avg Avg Avg Avg Avg Avg
2004-02-16 15:15:04.61 278822 31.08 24.23 25.12 26.8 24.14 24.47 23.76
2004-02-16 15:15:04.62 278823 31.07 24.23 25.13 26.82 24.15 24.45 23.8
2004-02-16 15:15:04.63 278824 31.07 24.2 25.09 26.8 24.11 24.45 23.75
2004-02-16 15:15:04.64 278825 31.07 24.21 25.1 26.77 24.13 24.39 23.76
See Section 2.4 Data Format on Computer for additional details on Logger
Memory and Data Structure.
Digital I/O task
Read and writes to ports and counters on CR9071
(ReadIO, WriteIO, TimerIO)
Processes measurements
Determines controls (port states) to set next scan
Stores data
Analog measurement and excitation sequence and
timing
Sets ports on 9060 Excitation Module (SetPort)
Sends interrupt to Processor task that reads and sets
ports/counters.
Polls CR9052 and CR9058 for Data
OV-21