MeasurementBlog

This eighth essay in a series on Sensorsmag.com. It is reproduced here with permission of SensorsMag a Questex Media Group, Inc. publication. The format has been slightly changed to make it easier to read online.

Jul 22, 2008 – by: G. Raymond Peacock, Temperatures.com Inc. – Sensors

This is the eighth essay in a series expanding on an article I wrote for Sensors titled “A Twelve-Step Sensor Selection Checklist.” In May, I talked about the process of soliciting bids. This month, I’ll focus on acquiring a sensor, or measurement device, and expert technical services.

A Source of Expertise
Keep in mind, the sensor supplier is an expert in the sensing area in which you are involved and a valuable technical resource, regardless of your own level of experience.
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Here’s the first chapter is a new series of articles on measurement devices or sensors: How to go about choosing them with care.

I originally wrote this as a single article for the November 2006 issue of Sensors Magazine. It was edited by their staff editor at the time and she did a wonderful job of helping get the best out of my thoughts and experiences.

This article and the balance of the series are online, as of December 2008, at www.Sensormag.com. They are reprinted here with links to the originals as a series and with the kind permission of the publisher of SensorsMag.com, Questex Media Group, Inc. Is is modified slightly in format to make it more readable on these Web pages.

Buying a sensor for the first time? Follow these steps to greatly reduce your chances of overlooking something important.
Nov 1, 2006, By: G. Raymond Peacock (Sensors)

Selecting a device to measure a physical property, such as temperature, can be a confusing process. But shortcuts and inattention to detail can get you into a real jam. Here, in chronological order, are the steps I try to use most of the time, especially when the measurement is really important.

The underlying concept is akin to the carpenter’s maxim: Measure twice; cut once.

1. Establish Measurement Span or Range Requirements

Find out your measurement range and any allowable variations. Many vendors specify accuracy or uncertainty as a percentage of measurement span. Be sure you understand what those specs mean. Many suppliers play fast and loose with the definition of terms as used in their literature. Some do a better job. And yet others omit some of those critical to your application: effects of ambient temperatures, especially the residual temperature coefficient; response time constant; or effects of vibration, radio frequency interference, or magnetic fields.
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