The global home healthcare services industry is already worth billions of U.S. dollars and, with a growing and aging population, this is expected to continue to increase. The industry includes any service that provides care in the home by trained professionals and, not surprisingly, there is a major trend toward the adoption of technology in this field.

Using technology to administer care is reshaping this industry. Key to its success is the ability to move medical equipment out of the hospital and into the patient's home.

Integration is the Key

Functional block diagram of the Photologic V 0PB9000 reflective optical sensor.

There is already a trend within the medical sector to make equipment more portable in the hospital; the ability to move diagnostic equipment to a patient's bedside instead of needing a dedicated room makes hospitals more efficient, while delivering higher levels of patient consultations.

Beyond diagnostics, the need for equipment that can monitor conditions and administer care is also increasing with an aging population. Often this requires a patient to visit a hospital for treatment but it is becoming more viable to provide this care in the patient's own home.

Some of the technology that drives medical equipment is subject to Moore's Law, which basically states that the capability of integrated circuits doubles every two years. An important aspect of this theory is that the size of devices doesn't increase and in most cases actually shrinks. This means that as integration scales, it becomes easier to design equipment that does more without increasing in size or, more pertinently, it can deliver the same performance in a much smaller footprint. It is this law that is helping to fuel the home healthcare industry, at least in terms of the technology needed.

Of course, medical equipment isn't just made up of integrated circuits. Some parts of medical equipment simply can't be made any smaller physically, but the ability to make the electronics much smaller and consume less power can help compensate for this, allowing the overall dimensions of a device to approach a point where it becomes much more readily portable. And thanks to the level of processing power now available, it is increasingly possible to design equipment that is practically autonomous in its operation.

Connectivity is another important factor in this new era of home healthcare. The ability for devices of all types to connect to the Internet — the so-called Internet of Things — means that home healthcare equipment can be in constant contact with a professional healthcare provider. All of the patient's statistics can be accessed remotely, while the equipment itself can raise an alarm if it detects anything that might cause concern.

Robust Solutions

The Photologic V OPB9000 includes a fully integrated analog front end, on-chip processing, and a digital interface in a surface-mount package.
Portable equipment requires optical sensors that consume minimal power while being highly integrated and as small as possible.

Of course, the medical electronics market is already well established and imposes the highest standards on semiconductor manufacturers targeting this sector. Certifying components for use in medical applications requires the highest design and manufacturing standards.

This creates demand for high-quality, robust solutions. From a system level, medical equipment can be viewed as any other device, but at every level the components used must deliver a level of quality, reliability, and capability that surpasses the demands of almost any other sector.

Part of the challenge of developing medical equipment is the need to maintain a sterile environment, particularly if that equipment comes in contact with a patient. This can become even more challenging if the equipment is intended to be used in the home by the patient. In this scenario, it becomes necessary for the equipment to be self-diagnosing, by monitoring its own operating conditions. This invariably means the inclusion of many sensors that can detect the equipment's state, further compounding the design challenge.

An example may be a blood dialysis machine used in the home. The detection of a valid cartridge is essential, but so too is detecting the presence of waste products such as blood and possibly other bodily fluids. Home health equipment still needs to maintain the same levels of cleanliness found in a hospital, so the presence of waste products is clearly a potential health risk. Detecting this hazard and alerting the care provider or patient becomes part of the equipment's specification.

Optical devices are commonly used to address this risk because they provide a way of measuring and sensing a range of conditions without physical contact. Optical switches can be used to detect the presence or absence of consumables such as the cartridge, as well as other matter such as waste products.

If intended for use in portable equipment, these optical sensors must also consume minimal power while being highly integrated, as small as possible, and able to withstand a tough environment. One example of such a device is the Photologic V OPB9000 reflective optical sensor from TT Electronics, which has been designed for medical applications. It includes a fully integrated analog front end, on-chip processing, and a digital interface in a surface-mount package measuring just 4.0 × 2.2 × 1.5 mm. This level of integration in such a small outline represents a space savings of as much as 80 percent in circuit complexity. Robust, industrial grade resin allows the sensor to operate at a wide temperature range from -40 °C to +85 °C, ideal for the harshest environments.

In a medical application, this sensor can be used in a hospital, a lab, and portable equipment to detect media and cartridge presence, as well as contamination and fluid level. With a level of ambient light immunity of 25 klux, it can be used where other optical sensors can't. It also integrates a wide range of features not found in other devices, such as self-calibration and automatic gain control, temperature compensation circuitry, programmable contrast sensitivity, and an industry standard communication interface. The sensor can be calibrated to detect various reflective surfaces at different distances. An on-chip EEPROM is used to store the calibrated LED drive current level, sensitivity level, and output type, allowing the sensor to return to the correct levels and states upon the next power-up cycle. A brief status mode follows every calibration sequence allowing the user to ensure that the calibration was successful. In addition, the sensor has a fast response time of just 6 μs. Figure 1 shows a functional block diagram of the OPB9000.


There is growing demand for smaller and more portable medical equipment designed for use in the home. This, in turn, is creating demand for smaller and more highly integrated sensing solutions.

With a focus on reliability, simplicity and flexibility, the optical sensors are helping to drive the development of devices specifically for the home healthcare market.

This article was written by Walter Garcia Brooks, Field Applications Engineer for TT Electronics, Woking, UK. For more information, Click Here .