Dataloggers

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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
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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
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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
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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'