Pressure sensors: The top 10 things not to do

Elden Tolman, design engineer of the Automation Products Group and his team have heard and seen just about everything when it comes to level sensors and pressure transducers. They’ve detailed the top 10 things not to do with a pressure sensor. The order of this list was determined based on two factors: frequency of the mistake, and the seriousness of the offense.

08/13/2012


10: Calibration without reference

If you must recalibrate a sensor yourself, then be certain you have an accurate reference with which to calibrate. Otherwise, you will end up with an inaccurate sensor.

9: Ignoring enclosure protection ratings

If the application is one that experiences high moisture or humidity, then use a sensor that is rated for such environments. Using an indoor rated sensor in an outdoor environment is a poor choice, and will most likely result in moisture damage.

8: Under-ranging

If you are measuring ranges that are well below your sensor’s specified range, you are under-ranging. If the application range is below 50% of the sensor’s range, you are sacrificing resolution and accuracy. Accuracy is rated based on the full scale, so 0.25% of full scale is a larger error band for high pressure rated sensors.

7: Incorrect wiring

Always verify that a sensor has been wired properly, according to specification, before applying power. 24 Vdc is not the same as 120 Vac!

6: Improper handling of the diaphragm

The diaphragm is the sensing element of the pressure transducer. It needs to be protected from damage. Rough handling of the sensor often results in non-conforming sensors. This is more frequent with flush mount sensors when the diaphragm is more exposed.

5: Using as a tool

It is important to remember that you are working with instrumentation, not tools. They are not designed to be used as anchor points, hitches, or levers, and you must be careful about how you tighten them.

4: Over-ranging

If you are measuring ranges well above the specified range of your sensor, then you are over-ranging. While it is true that over-pressure specs are intentionally conservative, it is a poor practice to rely upon them long term. Over-pressure ratings are defined with the understanding that it will be a rare occurrence. These ratings are not intended for standard operating ranges and will degrade the life of the sensor.

3: Improper ground

Multiple ground locations should be avoided. They can cause ground loops that will affect sensor performance, and can even compromise both wire shielding and surge protection. Electrolysis damage is a common result, particularly with submersible sensors.

2: Chemical incompatibility

If the wetted surface is not chemically compatible with the media being measured, it is only a matter of time before the sensor will fail. Even seemingly benign fluids and gasses can cause problems. For example, water is not compatible with all materials.

1: Wrong process connection

The threads of the sensor fitting or process connection need to match up and be properly rated for the pressure that will be applied. Not doing so will likely result in either damage to the process connection or in creating an unsafe situation. This is especially true in high pressure situations.



No comments
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
Each year, a panel of Control Engineering editors and industry expert judges select the System Integrator of the Year Award winners.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Learn how to create value with re-use; gain productivity with lean automation and connectivity, and optimize panel design and construction.
Go deep: Automation tackles offshore oil challenges; Ethernet advice; Wireless robotics; Product exclusives; Digital edition exclusives
Lost in the gray scale? How to get effective HMIs; Best practices: Integrate old and new wireless systems; Smart software, networks; Service provider certifications
Fixing PID: Part 2: Tweaking controller strategy; Machine safety networks; Salary survey and career advice; Smart I/O architecture; Product exclusives
The Ask Control Engineering blog covers all aspects of automation, including motors, drives, sensors, motion control, machine control, and embedded systems.
Look at the basics of industrial wireless technologies, wireless concepts, wireless standards, and wireless best practices with Daniel E. Capano of Diversified Technical Services Inc.
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
This is a blog from the trenches – written by engineers who are implementing and upgrading control systems every day across every industry.
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Case Study Database

Case Study Database

Get more exposure for your case study by uploading it to the Control Engineering case study database, where end-users can identify relevant solutions and explore what the experts are doing to effectively implement a variety of technology and productivity related projects.

These case studies provide examples of how knowledgeable solution providers have used technology, processes and people to create effective and successful implementations in real-world situations. Case studies can be completed by filling out a simple online form where you can outline the project title, abstract, and full story in 1500 words or less; upload photos, videos and a logo.

Click here to visit the Case Study Database and upload your case study.