Transcript Dataloggers
Dataloggers Dataloggers • Records voltage, current, or circuit closing • Environmental variables must be converted to electronic signal Dataloggers • Common loggers in Hydro Science – Campbell – Hobo – Many others Campbell CR10X, 800, 1000 • Loggernet software • Review Components – Analog voltage input • Single ended – Voltage measured relative to AG • Differential – Voltage on H measured relative to voltage on L (page 7-3) – Power • • • • 12V supply, G, Earth Ground 12V out 5V out Sw12V out Campbell CR10X, 800, 1000 • Components – Pulse inputs • Counts circuit closing – Control ports • Digital in and out • Most commonly used to turn things on and off • Can be programmed as a digital input – Excitation outputs • Supplies a specified voltage Campbell CR10X, 800, 1000 • Memory – Flash EEPROM stores operating system and programs – SRAM stores data and runs program • Data storage – Input storage – temporarily stores measurement or calculation results – Intermediate storage – used by the logger to move things around – Final storage – data stored for transfer (62,000 locations) Campbell CR10X, 800, 1000 • Programming sequence (table) (see OV-9) – Execute table – Measure (chapters 9-12 • • • • Excite sensor with appropriate delays (if needed) Measure voltage Store input Check – Output processing Campbell Files Sample Program • Thermistor measurement – Demonstrate single sensor through output • Thermistor.csi – Modify program from 2 thermistors • Illustrate sequential memory locations • Illustrate loops for calculations – Modify program for a thermocouple Multiplexor • Enables multiple sensors per input channel – Repeat measurements of the input channel – Mechanical switching of “sets” between measurements • Connections – CLK – Resets to open, no sets connected – RES – Advances the connected set by 1 – COM – Common port connected each set to datalogger More Instrumentation Vocabulary • Communication Protocol – How is information (signal) transferred from sensor to logger? • http://www.lammertbies.nl/comm/cable/RS -232.html#pins – Analog to digital conversion – Serial (RS232, RS422, RS485) – SDI 12 – USB Analog Sensor –Digital Conversion • Analog – Continuous, time varying transmission • Thermocouple generates an continuous analog voltage – Volt meter “samples” the continuous signal by a variety of methods to generate a discrete, digital output – CR10x analog inputs convert to digital memory Digital Sensor • Sensor contains microchip with internal A/D converter – Signal transmitted digitally • Logger receives a series of numbers, rather than raw voltages – CR10X control ports can be used as digital inputs Digital Sensor • Serial (RS232, 422, 485) – Different protocols (rules) for transmitting digital information Digital Sensor • SDI 12 – Developed by USGS • • • • http://www.sdi-12.org/ Becoming standard for environmental sensors Sensor delivers a “string” of numbers Sensor must be given an address Stevens Hydraprobe • http://www.stevenswater.com/catalog/stev ensProduct.aspx?SKU='93640'