Every month, Control’s editors take a specific product area, collect all the latest, significant tools we can find, and present them here to make your job easier. If you know of any tools and resources we didn’t include, send them to firstname.lastname@example.org, and we’ll add them to the website.
POSITIONING STRAIN GAGES
"Strain" is defined as the ratio of the change in length to the initial unstressed reference length. A strain gage is the element that senses this change and converts it into an electrical signal. The important factors that must be considered before selecting a strain gage are the direction, type and resolution of the strain you wish to measure. This PDF discusses each of these factors, and includes equations showing the relationships among stress, strain and force for bending, axial, shear, and torsional strain. The direct link is at http://tinyurl.com/4kquvur.
PRESSURE GAUGE SELECTION
This PDF discusses seven criteria to be used when choosing a pressure gauge. These include accuracy, dial size, case style/material, media/wetted parts, connection size, connection location, and pressure ranges. The direct link is at www.ashcroft.com/tech/upload/AshBulG_7.pdf.
Part of National Instruments’ series of tutorials on process measurements, this tutorial covers the following subjects: what is pressure? the pressure sensor, pressure measurement, signal conditioning for pressure sensors, DAQ systems for pressure measurements and references for further study. The direct link is at http://tinyurl.com/6aun4yu.
PRESSURE CONTROL APPLICATIONS
There are many good reasons for reducing (and sometimes maintaining) steam pressure. This tutorial details common applications for direct operating, pilot operated, pneumatic, electric and electro-pneumatic pressure control systems, including the advantages and disadvantages of each different control method. The direct link is found at http://tinyurl.com/4g73jbs.
PRESSURE TRANSDUCER HANDBOOK
Setra Sensing Solutions
This downloadable PDF is an introduction to capacitive pressure transducers. It contains material on comparisons with strain gages, transducer types, capacitive pressure transducer applications, transducer electrical connections, a glossary of terms, a conversion chart and more. The direct link is found at http://tinyurl.com/4sv3m8o.
SELECTING A PRESSURE SENSOR
This tutorial offers a five-step approach to selecting a pressure sensor. Items to consider include what exactly you wish to measure; the price you are prepared to pay; your precise application; the type of pressure you wish to measure; and the importance of selecting and instrument at the same time you select your sensor. The direct link to the tutorial is at http://tinyurl.com/4oal4ur.
CHOOSING AN I/P TRANSDUCER
I/P transducers are versatile instruments that use an electrical control signal to proportionally regulate gas pressure. The most common application is in valve actuation, but they can also be used in many other situations. As more processes become automated, I/Ps are replacing manual regulators. The information in this white paper should provide you with a complete understanding of the factors involved in making the correct product selection, installation and maintenance. When chosen, installed and maintained correctly, I/Ps should provide many years of reliable service. The direct link is at http://tinyurl.com/6hycctb.
PRESSURE CONTROL OPTIMIZATION
This paper discusses distillation column pressure regulation. They must be operated under constant pressure if temperature is to indicate composition. The primary advantage of floating pressure control is that, at minimum pressure, the required heat needed at the reboiler is minimized. The disadvantage is that the operating temperature is no longer an indication of composition. It needs compensation. The direct link to this paper is found at http://tinyurl.com/4aj5owq.