Designing the sensor elements of monitoring or control systems which require accurate, reliable, real-world inputs can be one of the most challenging parts of the product development cycle. It's no wonder then, why many designers now opt to purchase either off-the-shelf or custom pre-integrated sensor modules.
Offloading most of the design, test, and manufacture of sensing elements to a third-party vendor can help make the most of an engineering team's limited resources while shortening a product's time-to-market. Nevertheless, there are still many critical decisions a designer must make which have a major impact on their products' performance, reliability, and cost.
To help design the optimal system, let's look at pre-integrated sensor elements -- specifically the advantages they offer -- and familiarize you with some of the key issues you must consider to create a solution which best meets your application's requirements. Even an experienced engineer may find that designing the sensor elements which provide accurate, reliable data about the real-world conditions within HVAC systems, medical devices, process control, or other factory automation equipment can be one of the most time-consuming and expensive parts of a product development cycle. This is in large part because sensor design is an interdisciplinary process, which requires a design team to consider myriad electrical, mechanical, and manufacturability issues.
Once you've identified the sensor element(s) best suited to your application, you must decide how to integrate it with the rest of the system. This process includes pairing the sensor with the right combination of signal-conditioning circuitry, termination, and interface connector. Next, it's time to decide whether there's a standard off-the-shelf package that can house the resulting assembly or if your application's space and environmental requirements are best met with custom-fit packaging. A custom package may even integrate one or more sensors and other elements to create a next-higher assembly, such as a pressure sensor with an integrated manifold for use in blood analyzers and ventilators.
Remember, too, that as the sensor design evolves, so must its test plan. Your design must include the procedures needed to verify that the final assembly will operate accurately and reliably when it's integrated with its host system.
The case for an integrated sensor
Pre-integrated sensor solutions are becoming a popular and increasingly cost-effective alternative to the traditional sensor selection and integration process. In many cases, careful selection of a single known-good package, which may include the sensor (or multiple sensors), signal conditioning elements, and other critical components, can help accelerate a product's development schedule while reducing its design, manufacturing, and test costs. This can also help manufacturers shorten the certification testing schedules because once an integrated solution is certified to comply with an industrial or medical standard; developers who use it in their design don't have to recertify their upgraded products (figure1).
In most cases, any cost differential between pre-integrated/pre-tested sensor assemblies and discrete components is repaid several times over with lower unit production cost and reduced testing costs. Using pre-integrated sensor solutions also eliminates the overhead associated with maintaining and tracking the many discrete components a manufacturer would have to stock