NET Facility Logger: North Walls 7/8

WSU Puyallup Research Extension

Patrick O'Keeffe
Voiland College of Engineering and Architecture
Washington State University

Acquire data from recently installed sensors...
- many point moisture measurements (PMM Sensor; SMT Research)
- many embedded moisture sensors (EMS Sensor; SMT Research)
- a few rel. humidity & temperature sensors (HTM2500; SMT Research)
using existing datalogger infrastructure:
- (2) microloggers (CR10X; Campbell Scientific)
- (9) AM16/32A multiplexer (AM16/32A; Campbell Scientific)
- (1) datalogger (CR1000; Campbell Scientific)

Reviewed wiring diagram
- Identifies possible typos
- Suggests circuit revision for HTM2500 RH measurements (tie DF input low side to earth)
Wiring diagram reviewed by PI
- Returned with some edits
On-site visit by PI
- Review flagged cells... and update wiring diagram
- Take photos of installation
- Positively identify each MUX unit
Fix-up sensor hardware integration
- Per discussion with PI, most sensors are resistive (thermistors)
- Thermistor-based sensors require additional integration circuity → construct resistor half-bridge
- Multiplexers designed to read consecutive blocks of identical sensors → reorganize sensor input locations

A workable approach to thermistor integration:

Notes:

precision resistor
- resistive value: 10kOhm is commonly used, reduces impact of lead wire resistance
- low tolerance: 0.02% (CSI recommended) or 0.1% (spec of Model 107 probe)
- low temperature coefficient: no more than 5ppm/°C (CSI recommended)
excitation voltage
- CSI typ uses 2VAC
- some examples used 0.5V
temperature polynomial
- datasheets specify Beta values.. do they also include Steinhart-Hart coefficients?
- still need to identify "a, b species correction regression coefficients" mentioned in datasheets

Campbell Scientific Inc. AM16/32A Relay Multiplexer Instruction Manual. Revision Nov 2007. Online: https://s.campbellsci.com/documents/us/manuals/am16-32a.pdf
- Section 6.3.1 - Half Bridge Measurement with Completion Resistor at Datalogger
Campbell Scientific Inc. CR10X Measurement and Control Module Operator's Manual. Revision Feb 2003. Online: https://s.campbellsci.com/documents/us/manuals/cr10x.pdf
- Section 7.15 - Nonelinear Thermistor in Half Bridge (Model 101 Probe)
Campbell Scientific Inc. Model 107 Temperature Probe Instruction Manual. Revision Feb 2018. Online: https://s.campbellsci.com/documents/us/manuals/107.pdf
- Section 8.1 - Sensor Schematic
- Section 8.2 - Measurement and Output Linearization
Campbell Scientific Inc. Using Thermistor Temperature Sensors with Campbell Scientific Dataloggers. Technical Note 15-95AS. Issued Nov 2005. Online: https://s.campbellsci.com/documents/us/technical-papers/csl_thermistors.pdf
SMT Research Ltd. Embedded Moisture Sensor (EMS) Datasheet. Revision C. Online: http://docs.smtresearch.ca/EMS_Datasheet.pdf
SMT Research Ltd. Point Moisture Measurement (PMM) Sensor Datasheet. Revision H. Online: http://docs.smtresearch.ca/PMM_Datasheet.pdf
SMT Research Ltd. Relative Humidity Sensor (HTM2500) Datasheet. Revision B. Online: http://docs.smtresearch.ca/HTM2500_Datasheet.pdf
Other bookmarks:

Name		Name	Last commit message	Last commit date
Latest commit History 8 Commits
images		images
.gitignore		.gitignore
Wiring Info for Yadama Walls (new MUX inputs).xlsx		Wiring Info for Yadama Walls (new MUX inputs).xlsx
Wiring Info for Yadama Walls.xlsx		Wiring Info for Yadama Walls.xlsx
halfbridge_wiring.png		halfbridge_wiring.png
mux_layout.png		mux_layout.png
readme.md		readme.md