When it comes to measurement, the ultimate goal for operators in the process industries is to find a trouble-free, loop-powered level transmitter that can be mounted, wired and forgotten. As instrument shops’ staffing has been whittled back to a minimum, it has become the goal of many manufacturers to meet that challenging need for “plug and play” devices. So, how close have we gotten to applying two wires and walking away? This blog post explores the search for non-contact radar nirvana and how radar technology has evolved over the years.
A History of Radar Advancements
In the late 1990s and early 2000s, low-cost, loop-powered radar burst onto the scene. It was enthusiastically applied due to its ability to work even in the changing conditions that plagued the most popular technologies of the time. No longer would changing specific gravity ruin the accuracy of DP cells or displacers, or changing dielectric spoil the performance of RF capacitance devices, or vapor space changes affect the propagation consistency of ultrasonics. In short, a new age was upon us.
The Pulsar® Model R86 radar transmitter.
Radar had already evolved into two variations: Non-contact/through-air (antenna-based) and contact/guided wave (probe-based). In a perfect world all transmitters would be non-contact so they would not have to contend with contacting the dirty, coating-prone, turbulent liquids that can wreak havoc with performance and mechanical integrity. However, since guided wave radar (GWR) employs a metallic probe, a highly efficient electrical path is provided to propagate the signal. This allows for extremely strong radar reflections from the liquid surface, thus providing excellent performance in difficult conditions.
A Love-Hate Relationship
Non-contact radar (NCR) slowly became the technology many people love to hate. Theoretically, NCR can be so effective it should be everyone’s first choice. It is small and easy to install. This means that measurement in tall tanks does not necessitate a long, expensive and unwieldy probe like GWR, and the device sits up high in the tank, away from the tank contents. However, the vagary of launching an electromagnetic signal into space and waiting for its return is fraught with potential complications: false reflections from objects in the vessel, severe turbulence that can scatter the signal and foam that can absorb it are just some of the issues that exist to render NCR ineffective. Users reported challenges getting these devices ideally configured, which discouraged others from using them.
The Goldilocks Dilemma
Two of the keys to the effective use of NCR are correct installation and proper configuration. Installation includes avoiding sidewall and false target reflections. Configuration is getting the gain (amplification) settings just right. This is the “Goldilocks dilemma”— it can’t be too hot or too cold—too hot (excessive gain) and the echo saturates (distorts), deteriorating accuracy; too cold (insufficient gain) and the weak signal is lost. Optimal configuration is not an impossible task, but it is one that has eluded many good instrument personnel.
How Circular Polarization Helps
Electromagnetic energy can be launched using linear or circular polarization. Linear polarization has a constant E-field and needs adjusting to avoid sidewall reflections. To remove these launcher adjustments, the new Pulsar® Model R86 non-contact radar transmitter from Magnetrol® employs circular polarization which has a rotating E-field. In this way, no antenna adjustment is necessary during commissioning, getting the user closer to the “plug and play” goal.
When configured properly, the Model R86 can be everyone’s go-to transmitter. Having said that, no transmitter ever made is totally trouble-free. But if problems occur, MAGNETROL should have the ability to diagnose them quickly and bring the device back on line as fast as possible.
That means no more waiting for the trouble-free, loop-powered level transmitter that can be mounted, wired and forgotten. Non-contact radar nirvana is finally here.
For more information about this new innovation in non-contact radar, visit r86.magnetrol.com.