Reference Recorders: “New Kid on the Block” Is Driving Change in Pressure Measurement

By David K. Porter, March 21, 2014

David K. Porter, P.E. is the division vice president, Crystal Engineering business manager at AMETEK, Inc. He has over 25 years experience; the last 13 years were spent in the test and measurement field developing rugged, highly accurate, and easy-to-use instruments. He has a degree in mechanical engineering from California Polytechnic State University, San Luis Obispo, where he is active on the Industry Advisory Board.

Within the pressure measurement industry, relentless innovation has become the norm. New technology continually supplants the old, providing higher quality, lower cost and often both. Today, reference recorders are shaking up old standards in the oil and gas, chemical processing, power generation and wastewater treatment industries.

What is a Reference Recorder?

A reference recorder is a new class of instrument that is gaining ground over other common pressure instruments. While chart recorders, deadweight testers and analog pressure gauges all brought several advantages in their time, reference recorders are demonstrating the ability replace all three with a single instrument. 

Reference recorders unify the recording capability of a chart recorder, the high accuracy of a deadweight tester, and the continuous measurements of a pressure gauge into one tool that is easier to use and less expensive.

On their own, none of these features is unique, but when you put them all in the same device and make it cost-effective, you end up with something really useful. Offering reference recorders for both laboratory and field applications has real advantages for the user.

While data logging devices are nothing new, improved microprocessors allow today’s reference recorders to read and record faster and more accurately than previously.

Reference recorders detect readings from modules that read pressure, temperature, current or voltage and store the data in digital memory. These modules are usually interchangeable and recorders generally accept two inputs at a time. In addition to their compact size, reference recorders offer several improvements over bulky chart recorders.

Improving On a Chart Recorder

Originally patented in 1915, chart recorders produce a graph on a moving paper chart, relying on ink pens mounted on mechanical arms, which pivot in response to pressure. Their primary advantage is the ability to record for extended periods in remote locations. Chart recorders may be battery-powered or entirely mechanical (requiring no external power), allowing them to operate in hazardous locations. 

An experienced user may provide preliminary analysis on the output from a chart recorder in the field. Communicating or storing this data electronically becomes possible only after a technician enters or scans the chart into a computer. This process typically takes several days before results become available. 

Chart recorders typically claim an accuracy ranging from 0.25 percent to 1 percent of span, but that figure depends on changes in ambient temperature and on the thickness of its pens – which can cause an additional error up to 1 percent of the recorded reading. Chart recorders are also susceptible to errors caused by overpressure, and can easily be damaged if dropped.

In contrast, a reference recorder exports digital data