Board mount pressure sensors (Figure 1) are already being used in a number of applications including medical devices, industrial automation, and HVACR. But why might they be chosen over more traditional pressure sensing systems?
Board mount pressure sensors, as the name implies, are pressure sensors designed to be mounted on a PCB (Printed Circuit Board), thus becoming an integrated part of an electronic assembly. While some sensors are designed to evaluate the physical contact pressure between a sensor and a solid object, others are specifically intended to measure the pressure of a liquid or gas.
Benefits of Board Mount Sensors
In general, board mount pressure sensor’s benefits lie in including the sensors and ASIC (Application Specific Integrated Circuit) on a single chip that is easy to place, even on very crowded PCBs.
Such an approach:
- Reduces part costs
- Simplifies design complexity
- Lowers system footprint
- Increases design flexibility in sensor implementation
In addition, some of these sensors include calibration, amplification, and temperature compensation integrated into a single package which:
- Enhances system uptime
- Makes the replacement of sensors much easier
- Creates a more compact and lightweight footprint of pressure measurement systems.
Another benefit is how these sensors are designed to work in environments that involve high levels of humidity and/or exposure to various fluids and gases. This allows the sensor to be directly exposed to the media being measured, which can be extremely important in applications such as ventilators or sleep apnea machines (see Figure 2).
Finally, there are certain types of these sensors that provide extremely high levels of accuracy along with good precision, resolution, and repeatability, all of which can be critical in many devices.
Types of Pressure for Pressure Sensors
Almost all board mount pressure sensors depend on some type of micro-level structure (e.g., diaphragm) that exhibits a change in an electrical characteristic that is proportional to the deformation it experiences when deformed.
The electrical characteristics may include a change in capacitance, resistance, or charge, all of which can be measured and transformed into an electrical signal.
The three types of pressures measured by pressure sensors are:
- Gauge pressure, the pressure relative to atmospheric pressure
- Differential pressure, the pressure difference between two points
- Absolute pressure, the pressure relative to 0 psi
In most cases, gauge pressure sensors provide an output that is proportional to any variation from atmospheric pressure while differential pressure is based on pressure measurements between two ports. Finally, absolute pressure sensors use an internal vacuum reference and are generally used to measure barometric pressure changes or altitude changes.
Applications: Medical and Industrial
Board mount pressure sensors are used in many different applications and industries (Figure 3), ranging from mission-critical medical devices to automated manufacturing.
They can be found in HVACR detecting clogged filters, assisting with environmental monitoring and IAQ (Indoor Air Quality), and building energy conservation.
These pressure sensors also work well for measuring static duct pressure, detecting the presence of filters, and supporting VAV (Variable Air Volume) control.
In the medical industry, they have proven indispensable in various equipment including:
- Anesthesia machines
- Hospital room air pressure
Board mount pressure sensors are also used in equipment related to blood analysis, dialysis, centrifugation, and distribution of gases such as oxygen and nitrogen.
In an industrial context, these sensors are used in:
- General machinery
- Condition monitoring
- IIoT (Industrial Internet of Things) devices
- Industry 4.0
These sensors are used in industrial settings with:
- Pneumatic air control
- Process control
- Leak detection
- Weather control systems
- Vacuum switches
Choosing a Sensor: Specifications and Characteristics
Before choosing a board mount pressure sensor, it is important to understand some key specifications and characteristics of these sensors.
When it comes to the specifications of this type of sensor, these often include the output signal range and supply voltage. In addition, a choice must be made as to whether the output signal is ratiometric VDC analog or digital I2C or Serial Peripheral Interface (SPI), which can be directly interfaced to a microprocessor or microcontroller.
Analog or digital also impacts how often the data values can be updated, which is typically measured in kHz.
As for basic characteristics for board mount pressure sensors, these often include:
- Range–minimum and maximum pressure that the sensor can accurately detect
- Resolution–minimum pressure change that has to be present in order for the output signal to reflect it
Keep in mind that there is a relationship between range and resolution: the higher the range, the less resolution is possible and vice versa.
In addition to the standard pressure characteristics, it is wise to consider burst pressure. Some applications, including those in the medical field, may involve cleaning or sanitation procedures that can lead to a temporary but significant increase in pressure. Pressure spikes that although transient still exceed the overpressure limit for the device.
Another key characteristic to consider is temperature. Since the temperature has a significant impact on pressure, some (but not all) board mount pressure sensors are temperature compensated for factors such as:
- Sensor offset
- Temperature effects
This temperature compensation is often accomplished through the use of on board ASICs.
Accuracy, which indicates how closely the pressure value reported by the sensor is to the actual pressure being measured, is also crucial.
Accuracy is reported as a percent of the pressure sensors Full Scale (FS) or Full Scale Band Span (FSS). It may also be reported in terms of Total Error Band (TEB), which represents the sensor’s accuracy over a temperature-compensated range.
One final characteristic of these sensors involves the type of media that it works with (e.g., fluids, dry gases) and whether the media must meet additional requirements such as non-corrosive or non-ionic.
Though these are but a few specifications and considerations, it is necessary to consider each one while choosing which pressure sensor to select.
Honeywell’s TruStability Standard Accuracy Silicon Ceramic (SSC) Product Line
Overall, these sensors can be beneficial for applications that require a small footprint and direct exposure to media. When selected and integrated correctly, they can prove to be highly reliable with excellent accuracy over a wide range of pressures.
The Honeywell TruStability Standard Accuracy Silicon Ceramic (SSC) product line is one option for non-ionic, non-corrosive gases and liquids, including air and other dry gases, over a wide pressure range of ±1.6 mbar to ±10 bar (±160 Pa to ±1 MPa).
This family of sensors has been calibrated and temperature compensated for sensor offset, non-linearity, sensitivity, temperature effects (-20°C to 85°C), using an on-board ASIC, support high burst pressures, and meet IPC/JEDEC J-STD-020D.1 Moisture Sensitivity Level 1 requirement.
These sensors can measure gauge, differential, and absolute pressure and support ratiometric analog and I2C / SPI digital output.
In addition, these sensors include:
- Readings that are updated at 2 kHz for digital and 1 kHz for analog
- A total error of ±2% FSS to ±5% FSS, depending on pressure range, with industry-leading accuracy levels of ±0.25% FSS BFSL.
- A support sleep mode for energy efficiency.
- A wide range of porting and housing configurations to shorten the design and development time for engineers.
Sager Electronics is an authorized stocking distributor of Honeywell Sensing and IoT, offering a broad scope of TruStability board mount pressure sensors as well as other sensor and switching solutions.