ISA Interchange

Welcome to the official blog of the International Society of Automation (ISA).

This blog covers numerous topics on industrial automation such as operations & management, continuous & batch processing, connectivity, manufacturing & machine control, and Industry 4.0.

The material and information contained on this website is for general information purposes only. ISA blog posts may be authored by ISA staff and guest authors from the automation community. Views and opinions expressed by a guest author are solely their own, and do not necessarily represent those of ISA. Posts made by guest authors have been subject to peer review.

All Posts

AutoQuiz: How Do You Interpret Error Readings in Pressure Instrument Calibration?

AutoQuiz is edited by Joel Don, ISA's social media community manager.

Today's automation industry quiz question comes from the ISA Certified Control Systems Technician (CCST) program. Certified Control System Technicians calibrate, document, troubleshoot, and repair/replace instrumentation for systems that measure and control level, temperature, pressure, flow, and other process variables. Click this link for information about the CCST program. This question is from the Level I study guide, Domain 1, Calibration. Level l represents a professional who has a 5-year total of education, training, and/or experience.AutoQuiz-pressure-gauge-calibration-error

A 0-30 psig gauge is undergoing calibration. Starting at 0 psi, the technician applies a pressure of 15 psi. The gauge reads 14.9 psi. Then the technician applies 30 psi of pressure. The technician then reduces the calibration pressure to 15 psi. The gauge reads 15.2 psig. What type of error do these readings suggest?

a) hysteresis error
b) span error
c) zero shift error
d) linearity error
e) none of the above

   

Hysteresis is that phenomenon of an element, or in this case the instrument, whereby the value of the output (14.9 psi) for a given excursion of the input (calibration tool's pressure-15 psi) depends upon the history of the prior excursion (increasing values from 0 psi) and the direction (increasing or decreasing) of the current traverse.

In this example, the first excursion is the increase from 0 to 30 psi stopping at 15 psi along the way. The second excursion is the decrease from 30 psi to 15 psi. The reading on the instrument going up in pressure at 15 psi was 14.9 psi. The reading coming down from 30 psi to 15 psi, at 15 psi, was 15.2 psi.

20050323

The x-axis is the calibrator input. The y-axis is the reading of the instrument which we are calibrating. Span error, when displayed on an input/output calibration graph, translates as a line that is not parallel to the ideal line. That is to say, both lines are straight, but their slopes are different. Zero error will show up on a calibration graph as two lines that are parallel because the shift is not only present at zero, it is constant throughout the range of the instrument.

The correct answer is A, hysteresis error.

 

Joel Don
Joel Don
Joel Don is an independent content marketing, social media and public relations consultant. Prior to his work in marketing and PR, Joel served as an editor for regional newspapers and national magazines throughout the U.S. He earned a master's degree from the Medill School at Northwestern University with a focus on science, engineering and biomedical marketing communications, and a bachelor of science degree from UC San Diego.

Related Posts

Unlocking the Next Wave of Automation Careers: AI, ML and Smart Technologies Leading the Charge

A previous ISA article in 2023 considered how the future automation workforce is being shaped by an Indus...
Steve Mustard Nov 22, 2024 7:00:00 AM

Advance Your Automation Career in the 2024 ISA Black Friday Week Sale

Black Friday sales are a well-known revenue juggernaut around the world. In the U.S. alone, Black Friday ...
Kara Phelps Nov 19, 2024 7:00:00 AM

Checking In With Mimo, ISA's Large Language Model Trained on ISA Content

Over the summer of 2024, the International Society of Automation (ISA) announced a large language model (...
Kara Phelps Nov 15, 2024 7:00:00 AM