Thursday, December 15, 2011

Water Monitors in Action

Thieves, vandalism. . .and thousands of irate phone calls. All in a day (or two’s) work for the municipal water department in the South African province of Pietermaritzburg. As this story details, a water outage a few weeks ago led to a bit of detective work, lots of walking, a night robbery, and, ultimately, a happy ending for a dried-up city and a few workers. And it all started with telemetry.
The first sign of a problem – even before citizens began complaining about a lack of running water – was detected at a central station connected to the system of water monitors in place throughout the city’s reservoirs and pipelines. Since municipal monitoring equipment is a specialty of ours here at Devar, this prelude to what followed is what caught our eye. As the water superintendent and other workers set out to discover the cause of the problem, a remarkable convergence of science and intuition allowed the chief to determine just what was going on, and where it was happening.
State-of-the-art monitoring equipment is often indispensable, and at the least, a key supporting element of any water system. But 30 years of human experience can’t be replicated by a machine, and that’s what the superintendant drew upon when his ears told him that the water flowing through the pipes just didn’t sound right. For all the talk of real-time monitoring and instant fixes, there’s no method more direct than just listening, if you can.
For the full story, be sure to read the article. It’s quite a tale, and – spoiler alert – the water does get turned back on in the end. For answers to any further questions about water monitoring and telemetry, contact Devar today!

Tuesday, December 6, 2011

Why and How? A Discussion of Loop Powered Indicators

When selecting a signal indicator, “loop powered” is a phrase that you may come across often. While extremely useful, it’s not always clear to our customers what, exactly, this technology consists of – and how it can help them. This is a very basic explanation of the theory behind, and the purpose of, loop powered indicators.

The most important thing to understand about loop power (or “current loop”), is that it helps maintain the accuracy of signal readings when the distance between a sensor and the monitor is very long. This is because, traditionally, a sensor will transmit information as electrical voltage. Voltage can be lost due to resistance during transmission, resulting in an inaccurately low reading by the monitor. Loop powered indicators solve this problem by converting voltage to electrical current, which is, by definition, the movement of electrons from one point to another. Electrons are much less likely to be lost in transmission than voltage.

So, a loop powered indicator converts a unit reading to a voltage, which is in turn converted to a proportional current figure between 4mA and 20mA (the meaning of the typical 4-20mA current loop). This is converted back to a voltage on the monitor device, either appearing as a display or being processed as a data reading.

For greater detail on the current loop process, see Current Loop.