Choosing the Pressure Sensor That Is Right for You

Pressure sensors are available in several applications. However, the type of sensor you end up choosing depends on several things. When picking a pressure sensor, it’s important to remember that there are three types of pressure to consider, each of which corresponds to a particular sensor design.

For example, did you know that the deformation of a membrane as a result of the pressure put on it is measured by most pressure sensors? And did you also know that it is this value that is vital? That is because the membrane has two sides, and this means that a different pressure is applied to the second side. The measured deformation is the consequence of the pressure differential between the two sides.

That is why it is important to consider what you will need your pressure sensor for. This will help you determine the best sensor that is going to fit your current needs. When you’re thinking about purchasing a pressure sensor, there are going to be three options for you to choose from. The three sensor options are:

• A Differential Pressure Sensor – A differential pressure sensor contains two inputs, one for each side of the membrane, and its deformation is proportional to the difference in pressure between the two inputs. Pressure dips over oil filters or air filters, fluid levels (by comparing the pressure above and below the liquid), and flow rates are all measured with differential pressure sensors (by measuring the change in pressure across a restriction).The differential pressure sensor will provide you with a comparison of two places, like before and after a valve in a pipe, for example. The pressure on both sides should be the same if the valve is fully open. If there’s a pressure differential, it’s possible that the valve isn’t entirely open or that there’s a blockage.
• An Absolute Pressure Sensor – An absolute pressure sensor is the instrument of choice for measuring air pressure, especially for applications such as barometer readings for weather or in altimeters. However, you aren’t confined to using air or gas in your applications. The second side of the membrane in an absolute pressure sensor is under vacuum, and its deformation matches perfectly to the recorded pressure. The measurements from absolute pressure sensors and gauges are unaffected by air pressure. Altimeters and barometers, for example, show vacuum-referenced absolute pressure data. The absolute measurement is done by comparing the goal pressure to the known absolute vacuum pressure. This is similar to measuring temperature in Kelvin, where the lowest temperature achievable is 0 °K.
• A Relative Pressure Sensor – When you want to avoid the effect of air pressure on your measurement, a relative pressure sensor comes in handy. This type of sensor is used to measure a fixed or changeable value. Consider a thermocouple, which measures the temperature differential rather than the actual temperature. In a relative pressure sensor, the second side of the membrane is exposed to air pressure, thus its deformation corresponds to the difference between the measured and ambient pressures.  The surface of the liquid in the vessel is also subjected to atmospheric pressure, and when a pressure sensor is used to measure the hydrostatic pressure of a liquid in a vessel to determine its level, the relative pressure sensor allows only the hydrostatic pressure to be measured. This thus eliminates the influence of variations in atmospheric pressure.

How to Choose Your Pressure Sensor

Once you understand the difference between the three sensors, you can narrow your options down. After deciding whether to measure absolute, relative, or differential pressure and selecting a sensor technology, you must still select the appropriate model based on a few factors. This way, you’re not blindly purchasing whatever looks like it might get the job done. Getting the job done is one thing. Getting it done right is something else entirely.

This is how you choose the right kind of pressure sensor for you:

• The Sensor’s Configuration Matters – The design of the sensor and how it is affixed to the site of measurement is one of your selection factors when you’re buying a pressure sensor. A lot of the sensors out there are threaded, making it much easier to put a nozzle on a pipe, tank, or other surface. There are also flanged sensors, small sensors that can be soldered into a circuit board, and so on. The use of flush diaphragm sensors provides its own set of benefits. The sensor membrane is flush with the pipe wall in this design, preventing clogging difficulties caused by material collection in locations where there is no flow. This arrangement is very beneficial in the food business for liquids containing solid components.
• Your Measuring Range Must Match Your Pressure Range – It’s critical to pick a sensor with a measuring range that matches the pressure range you’ll be monitoring. When you’re looking around for pressure sensors, you should be taking into consideration the usual conditions and any pressure changes before you make your selection.
• The Output Signal Must Correspond With The Control Loop – You must select a pressure sensor with an output signal that correlates to your measurement or control loop, just like you would any other sensor.
• The Operating Temperature Matters – It’s also crucial to consider the operating temperature. The majority of sensors have a temperature range of -25°C to 100°C. The sensor you choose will be based on what temperature range you need to measure. It’s essential to use sensors that can resist greater temperatures.

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