Handheld pH Scanner
Design Process
Applications
pH Meters have a broad usage base including industrial food processing, pool maintenance, general research in lab environments, and horticulture, to name a few. Below are examples of where certain everyday liquids fall on a pH scale.
The Problem
Current pH Meters are finicky devices that need to be calibrated often using buffer solutions, have to be stored in a liquid solution in order to prevent damage to the electrode, are extremely fragile due to a glass probe, and are subject to signal drifting causing inaccurate measurements.
A New Technology Platform
We worked with the start up, Senova Systems, to help them to design a device, from the ground up, for pH measurement based on a new technology platform that they had licensed. The technology allows for a robust pH scanner contained in a stainless steal tube that simply needs to be turned on and used. No calibration, no need to be stored in special solutions when not in use, doesn't suffer from signal drifting, and doesn't have a fragile glass probe. My goal as design lead was to complement this technology with a modern, progressive design, to provide a clear, concise user interface, and to consider the myriad use cases and device applications in the process. Our team consisted of a group of mechanical and electrical engineers, me as the design lead, a project manager, and a group of craftsmen/model makers.
Process
Below is an overview of the design process for this device. Concurrently, there was an electrical and mechanical engineering team. We worked together very closely over a tight timeline to produce the result below.
Defining the Internal Components
We spent a considerable amount of time and effort in deciding on the right components, particularly for the display. Due to power consumption, the software/electrical engineering team recommended we move away from an LCD display and consider a low power, transreflective display - the display you find in digital watches that gets brighter when there's more surrounding light. In the above sketches, we were looking at various silhouettes designed around a couple of different display sizes, a horizontal display on the right, vertical display in the center, and a smaller horizontal display on the left. We couldn't see a huge advantage in the larger, horizontal version (lots of empty space on the right and left plus not ideal for a hand held) and determined that the smaller more vertically oriented transreflective display served our purposes well.
Details and Refinements
Getting the right design for the buttons became quite a challenge, in part because of the strict limitations of the IP 6 liquid ingress qualification. This meant that every open seam on the device needed to be sealed to prevent water from seeping in. Because of this, the approach to the button interface that we decided to take was a two-button elastomer overmolded interface - a primary button to initiate the scan and a secondary button that served a dual purpose of both back lighting and, when held, turning the device on and off. The challenge became to adhere to the mechanical engineering team's overmolding requirements and getting the right level of hierarchy between the display read-out and the buttons.
Alpha Build
Our final deliverable was an alpha build of 16 fully functional devices. Below are some pictures taken by Rich, Continuum's incredible model shop director.