OpenOBS: Open‐source, low‐cost optical backscatter sensors for water quality and sediment‐transport research

Abstract

Optical backscatter sensors (OBSs) are commonly used to measure the turbidity, or light obscuration, of water in fresh and marine environments and various industrial applications. These turbidity data are commonly calibrated to yield total suspended solids (TSS) or suspended sediment concentration (SSC) measurements for water quality, sediment transport, and diverse other research and environmental management applications. Commercial sensors generally cost > $1000-3000. Here we leveraged simple, low-cost microprocessors, electronics, and housing components to design and construct open-source OBSs for < $150 per unit. The circuit relies on a photodiode to sense backscattered light, two stages of signal amplification, and a high-resolution analog-to-digital converter to read the detected signal. The instrument and logger utilize inexpensive, custom-printed circuit boards with through-hole soldering mounts; micro-SD card reader and real-time clock modules; and PVC housings with commercial end caps and epoxy-potted diode emitter and receiver. All parts are readily and publicly available, and minimal experience in soldering and coding is required to build and deploy the sensor. In lab and field tests, standard deviations were comparable to those measured by commercial sensors ($ 2-3% of the mean for suspended muds and 20-30% for suspended sands). These open-source sensors represent a useful advance in inexpensive sensing technology with broad applications across scientific and environmental management disciplines.

Hydrodynamics across seagrass meadows and its impacts on Indonesian coastal ecosystems: A review

“…Another pathway is to capacitate local scholars on the topic, including developing low-budget alternatives to hydrodynamic investigation and modeling and constructing low-cost parallel computers with high-performance computation capabilities (e.g., Costa et al, 2009;Jin et al, 2011). An example is the Arduino-based devices to record wave information (Lyman et al, 2020;Perales and Herman 2020;Eidam et al, 2022). Overall, if these constraints are addressed, they could further improve predictions on nearshore hydrodynamics impacts on seagrass ecosystems as well as progress on implementation strategies for seagrass restoration projects and natural protection in Indonesia.…”

Increased scale and accessibility of sediment transport research in rivers through practical, open-source turbidity and depth sensors

“…The OpenOBS project developed the rst eld-deployable open-source turbidity sensor with a wide range of linear response to sediment concentration 12 . The OpenOBS closely matches the design of commercial sensors by using a reverse-biased photodiode and transimpedance ampli er to give a linear response across a wide range of suspended sediment concentration values 15 (up to 5 g/L).…”

“…Even within the environmental monitoring subset of open-source sensors, a focus on technology development leads to publications that describe soldering, embedded programming, and the virtues of open source technology, rather than presenting scienti c applications 11 . While the low-cost of open-source sensors dismantles some barriers to science, compared to commercial sensors, do-it-yourself sensors have additional barriers in regards to: required knowledge of electronics accuracy and calibration ease of deployment Here, we present the OpenOBS-328 as a further re nement of the OpenOBS project 12 , improving on the three design principles above. The custom circuit board of the sensor can be completely manufactured by electronics assembly companies, leaving only the sensor head for the user to assemble.…”

Clarifying water clarity: A call to use metrics best suited to corresponding research and management goals in aquatic ecosystems

“…General metrics presented here include: Secchi disk depth (Z SD ) (Secchi and Cialdi 1866; Tyler 1968; Preisendorfer 1986), the downwelling and scalar light attenuation coefficients of photosynthetically active radiation (K d (PAR) and K o (PAR)) (Kirk 1994), turbidity (Zaneveld et al 1980; Davies‐Colley and Smith 2001; Sampedro and Salgueiro 2015; Eidam et al 2022), and beam attenuation (Bishop 1999). In this paper, the terms K d and K o will refer to K d (PAR) and K o (PAR).…”