Open Source Digitally Replicable Lab-Grade Scales

Abstract

This study provides designs for a low-cost, easily replicable open source lab-grade digital scale that can be used as a precision balance. The design is such that it can be manufactured for use in most labs throughout the world with open source RepRap-class material extrusion-based 3-D printers for the mechanical components and readily available open source electronics including the Arduino Nano. Several versions of the design were fabricated and tested for precision and accuracy for a range of load cells. The results showed the open source scale was found to be repeatable within 0.1g with multiple load cells, with even better precision (0.01g) depending on load cell range and style. The scale tracks linearly with proprietary lab-grade scales, meeting the performance specified in the load cell data sheets, indicating that it is accurate across the range of the load cell installed. The smallest loadcell tested(100g) offers precision on the order of a commercial digital mass balance. The scale can be produced at significant cost savings compared to scales of comparable range and precision when serial capability is present. The cost savings increase significantly as the range of the scale increases and are particularly well-suited for resource-constrained medical and scientific facilities.

A case study on enabling metrology in Africa with additive manufacturing

“…For example, the printing of expensive optical-mechanical components, which is used in many metrological fields, is shown in Salazar-Serrano et al (2017), while a design framework to improve the design of these components is introduced by Delmans and Haseloff (2018). Indeed, it seems that all fields of metrology and scientific experimentation are embracing AM in some way, for example, open-source microscopes and accessories (del Rosario et al, 2021;Tadrous, 2021), an interferometric small angular measurement device (Hussain and Nath, 2018), motion stages such as scissor jacks and translation stages (Mills, 2021;Zhou et al, 2019) (which are used extensively in metrology), chemical separators (Davis et al, 2021), integrating spheres (da Cruz Junior andBachmann, 2021), an open-source lab-grade digital scale (Hubbard and Pearce, 2020), a polarimeter (Harvie and Mello, 2021), a modification to a shaker used in accelerometer calibration (Veldman, 2021), low-cost ultrasonic wave propagation wedges (Balvantin et al, 2020) and indeed, in many other works, as reviewed in Pearce (2020).…”

Parametric Nasopharyngeal Swab for Sampling COVID-19 and Other Respiratory Viruses: Open Source Design, SLA 3-D Printing and UV Curing System

“…The first test was with synthetic nasal mucous (Kryolan, Cotati, CA) [68]. The dry swab was weighed on a calibrated open source digital scale [63]. Then, the swab was placed vertically in synthetic nasal mucous and massed again.…”

“…Tip abrasion tests were performed by 1) massing the dry weight of the swab on the open source digital scale [63], 2) placing distal end of swab (absorbent end) next to human tissue (inner left arm) and applying a rotation to proximal end (hand side -handle) at hand twirling speed for 10 seconds, and 3) the swab was removed wash and dried, and 4) massed. The difference in the pre and post abrasion test was recorded.…”

“…The components were massed on a calibrated open source digitally lab-grade scale[63]. The masses were 0.25, 1.91 and 4.14 grams for the swab, handle and tongs, respectively.…”