Campbell Scientific CR800 and CR850 Measurement and Control Systems - Manual (Page 59)

Section 5. System Overview
59
Sensors transduce phenomena into measurable electrical forms, outputting
voltage, current, resistance, pulses, or state changes. The CR800, sometimes
with the assistance of various peripheral devices, can measure nearly all electronic
sensors.
The CR800 measures analog voltage and pulse signals, representing the
magnitudes numerically. Numeric values are scaled to the units of measure, such
as milliVolts and pulses, or user-specified engineering units, such as wind
direction and wind speed. Measurements can be processed through calculations
or statistical operations and stored in memory awaiting transfer to a PC via
external storage or telecommunications.
The CR800 has the option of evaluating programmed instructions sequentially, or
in pipeline mode, wherein the CR800 decides the order of instruction execution.
5.1.1 Clock
Read More! See Clock Functions
(p. 483).
Nearly all CR800 functions depend on the internal clock. The operating system
and the CRBasic user program use the clock for scheduling operations. The
CRBasic program times functions through various instructions, but the method of
timing is nearly always in the form of "time into an interval." For example, 6:00
AM is represented in CRBasic as "360 minutes into a 1440 minute interval", 1440
minutes being the length of a day and 360 minutes into that day corresponding to
6:00 AM.
0 minutes into an interval puts it at the "top" of that interval, i.e. at the beginning
of the second, minute, hours, or day. For example, 0 minutes into a 1440 minute
interval corresponds to Midnight. When an interval of a week is programmed, the
week begins at Midnight on Monday morning.
5.1.2 Sensor Support
Read More! See Measurements
(p. 269).
The following sensor types are supported by the CR800 datalogger. Refer to the
appendix Sensors
(p. 537)
for information on sensors available from Campbell
Scientific.
• Analog voltage
• Analog current (with a shunt resistor)
• Thermocouples
• Resistive bridges
• Pulse output
• Period output
• Frequency output
• Serial and smart sensors
• SDI-12 sensors