Processing Magazine

In the doctor’s own words

December 6, 2013

Otek loop-powered tricolor LED bargraphThe significance of Tucson, Ariz.-based Otek’s product is best explained in the words of its founder, Dr. Otto Fest:

“When I started Otek Corp. in 1974 I wondered about the wasted energy in current loops, used only to transmit a signal over two wires to end up at an analog meter, valve or A/D converter controlling a process. This seemed a waste of both energy and information.

At that point someone developed the first liquid crystal displays (LCDs) and someone else the analog-to-digital (A/D) converter. My contribution was to develop the industry’s first loop-powered digital panel meter (DPM).

Up until then, current-loop instrumentation used the existing quiescent energy of the current loop (typically 24Vdc and 4-20mA) to operate. But anything other than the actual display of the measured value had to be externally powered.

Our technology requires less than 1% energy of comparable powered units (~10-50mW versus 1-10W) to operate its LED, multicolor bar, digital display; communicate serially with supervisory equipment; enable alarms; and retransmit current loops for monitoring and control or detect incoming loop or signal failure. All isolated from the incoming loop and all loop powered!

Just last year someone else improved the LED technology and someone else produced a nanotechnology ultra-low power microcontroller. Thus, 40 years following introduction of the industry’s first loop-powered DPM, we introduced the first fully automatic tricolor bargraph digital meter with on-off alarms, isolated serial I/O (USB or RS-485), isolated 4-20mA retransmission (externally loop-powered) and auto loop failure detection/alarm.

I am often asked, how can you claim loop-failure alarm when there is no current flowing in the loop?

To which I reply: “It’s simple, when the loop is normal we store energy. When we detect the loop dropping below 4mA we send a distress message via the serial loop to the user, turn off the bar graph and flash the display ‘LOOP FAIL’ until the stored energy bleeds — typically in about 20 seconds.”