Campbell Scientific CR1000KD CR800 and CR850 Measurement and Control Systems - Page 59

Section 5. System Overview 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 59