Selecting the correct accuracy for your sensing application is only half the challenge; being able to maintain that level of accuracy over time is equally important. To clarify on what we mean by the accuracy, we define it as the maximum difference between the actual value and the sensor’s output (in terms of %FS). Maintaining a sensor’s accuracy is difficult. Users face the issue of a sensor going out of tolerance and are unaware of the root causes. Depending on the level of accuracy required by the application, the consequences of imprecise accuracy can vary. For example, an isolation room requires a high level of accuracy to protect both the patients’ and medical professionals’ health and safety. If a room pressure monitor provided doctors and nurses with an incorrect sensor output, they can make incorrect judgments such as walking into a improperly labeled space. Based off of the inaccurate sensor output, doctors and nurses can also accidently release harmful contaminants into the rest of the hospital without a proper alarm notification.
By remaining proactive, the factors that can affect a sensor’s accuracy can be accounted for and controlled to prolong the life of the pressure sensor. Here are some of the main factors that can negatively impact or affect a sensor’s accuracy:
Application variables can change greatly depending on the type of application the sensor is used in and the pressure sensor selected. These types of variables typically affect the components of the sensor, prompting improper sensor performance. Below are a few examples of application variables that commonly go unnoticed but can affect the performance and accuracy of the sensor.
- Specific Gravity
- Dielectric Constant
- Shock and Vibration
- Barometric Pressure
Improper installation can also affect the sensor’s accuracy. A sensor must be mounted correctly in order to operate effectively. An improperly mounted sensor can lead to a shift in the output or premature sensor failure. The best way to avoid a shift caused by incorrect installation is by adjusting the zero offset via a zero adjustment potentiometer or by programming an offset into the sensor controller. If those options are not available, installing the sensor according to the manufacturer’s installation manual will ensure that there is no added error from installation orientation.
Natural Drift is referred to as a sensor’s yearly stability specifications and is a common occurrence for pressure sensors. The stability, or instability, of the sensor comes largely from the sensor’s electronics and/or diaphragm fatigue. A common method for controlling the natural drift of a sensor is calibration. It is important to note the magnitude or the rate of natural drift to determine the sensor’s calibration frequency. Knowing the needed frequency of calibration, allows the user to meet the desired accuracy in the application.
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