Archive for category Cost Issues

Industrial Wireless 101: Which wireless antenna do I need?

In our continuing quest to understand industrial wireless, here’s the next bite. We already talked about the three industrial wireless bands and what they’re used for. Now, we’ll look at wireless antenna.

The antenna’s primary purpose is to focus or direct the signal that it is sending or receiving. The antenna strength, called gain, (measured in decibels) concentrates the transmitter or radio signal in a given direction, and reduces it in unwanted directions. The higher the antenna’s decibel value, the more focused the signal.

I’ve found that the word gain sometimes confuses people: they think gain refers to an antenna ADDING power to a radio. That’s actually what an amplifier does. Antenna gain is about concentrating or dispersing radio frequency energy and directing it where it needs to go.  By packing that available energy into various patterns, as the different antenna types do, a radio signal can be spread out to a broad field or concentrated into a small tight pattern to go a farther distance.

Just like the three industrial wireless RF bands, there are three main types of antennas. And while lots of people have tried to explain them, with technical charts and inkblot-style diagrams, this simple description really hit home to me:

  1. Omni-directional antennas radiate their signal in all directions, like a floor lamp radiates light equally around itself.
  2. Semi-directional antennas radiate in a specific direction across a large area, like a spotlight shining on stage.
  3. Highly-directional antennas focus their signal on a very specific target, like a laser pointer focusing on a specific portion of a photo.

So, let’s take it a step further.

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Industrial Wireless 101: Why do we need three frequency bands?

Regardless of what information you need to send, or where you need to send it, if your data is going “over the air”, you’ll need to choose a frequency in one of three ranges that do not compete with the FCC licensed bands for radio transmissions.

These three ISM (industrial, scientific, medical) bands are 900 MHz, 2.4 GHz, and 5 GHz. They’ve often been described as the industrial equivalent to Citizens’ Band radios, specified so they don’t interfere with broadcast radio signals.

History with technology would lead you to believe that the more Hertz you have, the better your radios will perform. But what you need to understand is that there’s a tradeoff. Each band has its strengths and weaknesses, and there’s a best use for each.

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Using a wireless radio battery to power a pressure transmitter

In an ideal world, every place you need to install a transmitter would have easy access to electrical power. But we don’t live in the ideal world, and there are locations where power isn’t readily available, and getting electrical power to those areas can be quite costly.

This was the situation at a local plant, in their flammable fuel storage facility. The site is required to keep a record of the line pressure that supplies water in the event of a fire.

The Problem

The water pipe is located 6 to 7 feet (2 meters) below grade, and the engineers planned to build a vault where they could install and maintain the necessary submersible pressure transmitter.

The planned location is more than 500 yards from any available power source. The signal coming from the pressure transmitter would have to run that distance plus an additional 200 yards to reach the control room.

Not surprising, the trenching cost for an electrical installation was quoted at a five-figure minimum price.

Finding a solution

The project engineer started considering a wireless solution, and then asked, “Can a battery-powered industrial radio also power a two-wire loop-powered pressure transmitter?”

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Which temperature sensor do I need? An RTD or a thermocouple?

Temperature is probably the most measured parameter across applications and industries we work with on a daily basis. But there’s still confusion as to what temperature sensor to use.

I very often hear the Lesman inside sales team talking a customer through the selection process, so I thought I’d provide a quick tutorial on temperature sensor selection.

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