Radar-on-a-Chip Liquid Level Sensor

About seven years ago Tom McEwan, a scientist at Lawrence Livermore National Laboratory, had a brainstorm. McEwan soon sketched out plans for a radar system that would cost just a couple of thousand dollars to make, vs. $50,000 or so for the least expensive system at the time. When he showed his colleagues his idea they told him he was crazy. Before long McEwan figured out that he was, indeed, mistaken. Going over his figures again, he noticed a few obvious improvements that could reduce the cost to, at most, a few hundred dollars. Again, the same reaction from his coworkers.

A radar system for less than $500? Hold on to your seats. It turns out McEwan had overestimated the final production cost of his single-board radar system by a factor of a hundred. There was no practical barrier, McEwan told me in an interview in 1995, to mass-producing chip-sized radar systems for about $5 apiece. All the invention needed, I pointed out, was a catchy name rather than a 30-syllable tongue-twister concocted at the world's leading weapons laboratory.

Livermore's MIR features a complete radar system on a single chip.

Journalists covering high technology become adept at creating buzzwords and acronyms. While preparing my report I took "micropower" (McEwan envisioned his radar being powered by a AA battery), "impulse" (how the signal is transmitted), and "radar" and came up with "micropower impulse radar" (MIR), a name evoking space-age technology and which, I'm pleased to say, has stuck.

Practical Applications in Liquid Level Sensing
MIR is "gatable," meaning it can be tuned to receive signals from a predefined distance, rejecting echoes outside the desired measurement range. Gating makes MIR ideal for industrial and consumer applications, giving the technology broad mass appeal. McEwan, in fact, has become one of only a handful of scientists at national labs whose inventions have made them rich. It didn't take McEwan and Livermore long to come up with a laundry list of potential uses, including sensors for motion, proximity, and liquid level (germane to this article), microphones, imagers, trip wires, medical monitors, stud-finders, collision sensors for automobiles, and a couple of hundred others.

I had heard that hundreds of companies were lining up to license MIR (Livermore has 15 licensees signed up to date, with 20 more deals in the works). So I wasn't too surprised to come across a process industry product based on MIR at last week's Chemshow '99 in New York. Barton Instrument Systems LLC (City of Industry, CA) has turned MIR technology into a remote tank level measurement system. Barton's "TankScan," integrates a MIR radar-on-a-chip sensor with radiofrequency transmit/receive capability.

Barton touts TankScan as a "low-cost, high-performance remote distributed process inventory management hardware/software solution" requiring minimum installation expertise. TankScan's operation is simple. A pulse is sent down a weighted, flexible waveguide, returning when it hits the air/liquid interface inside the tank. Distance—and hence level—is determined by the time it takes for the signal to return.

Combining MIR low-energy, ultra-wide band impulse radar with high-frequency (optional 33 gigasample per second) transient digitizing, the battery-powered TankScan accurately measures level, with data transmitted by radio to a receiver from up to six data acquisition points. The receiver in turn sends data through a pre-programmed dialup modem to a desktop computer. There, Barton's DataScan PC software manages database and alarm functions, data analysis, reporting, and polling through an easy-to-use interface. Inventory status can be made available to host systems anywhere in the world via dial-up telephone or cellular modem using ADEPT or ModBus communication protocols.

Since no wiring is required and the complete system has no moving parts, TankScan installs inexpensively and requires almost no maintenance.

TankScan, Barton's MIR-based level sensor, was showcased at Chemshow ‘99.

Complete systems (MIR sensor, transmitter, receiver) sell for $795. According to Barton marketing manager Joe Incontri, most of the end-user cost for TankScan results from the packaging, which enables accurate operation over about a 25-foot range, and integration of the sensor chip with transmit and receive components. Although Barton offers several products that might benefit from MIR sensors, TankScan is Barton's only MIR product. The company is working on a second-generation receiver for TankScan that will acquire data from up to 32 data points.

For more information: Joe Incontri, Marketing Manager, Barton Instrument Systems, 900 S. Turnbull Canyon Rd., City of Industry, CA 91745. Tel: 626-961-2547. Fax: 626-961-4452.

By Angelo DePalma