Archive for category standards

Why has 4-20 mA gained so much acceptance and survived so long?

Last month, I presented a webinar for our customers. At the end of Control 101, when we opened the session up for questions, a customer asked about making the choice between 4-20 mA and digital signal outputs.  It got me thinking about this list I put together a while back — one that I pull out whenever customers ask me “Is 4-20 mA still valid?”

The answer: Yes, it is. And here are the 18 reasons I came up with… so far. Read the rest of this entry »

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What are DIN size panel cut-outs?

Instrument DIN cutout sizes in inches and millimeters

Years ago, instrument manufacturers adopted the DIN standard for panel mounted instruments, with standardized panel cutout dimensions for controllers, recorders, and other boxed mechanical devices.

And while the cut-outs are a standard size, the area occupied by the instrument’s bezel, its footprint, is not. Some bezels extend quite far beyond the cut-out, others barely extend beyond the cutout. 

So, you need to pay attention to both the cutout and bezel specs when you’re planning a first-time install or a replacement upgrade. A designer who lays out a panel needs to be aware of how close one panel mounted instrument can be to another.

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Industrial Wireless 101: Free access to webinar recordings

In the past month, I’ve focused several articles on industrial wireless technology. If you’re interested in learning more, here are several webinar recordings you can watch on your own time that will give you more insight into how wireless works, and how companies are using it to extend that measurement base and get process information where they need it to go, even on a limited budget.

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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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What does NAMUR NE 43 do for me?

People have asked me about setting fault alarms in level transmitter analog signals at 2mA or 3mA levels. What they typically don’t understand is that a two-wire transmitter uses the electrical current below 3.6 mA for its own power and operation. So, a 2.0 mA or 3.0 mA fault indication just isn’t possible. At these low currents, there wouldn’t be enough power to generate the fault indication signal and to keep the transmitter functioning properly. Read the rest of this entry »

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Are thermocouple heads and transmitters interchangeable between brands?

Ever wonder if you can mix brands of thermocouple heads, transmitters, or junction blocks?  The other day, I was trying to figure out if I could, and I ran into a spec I didn’t understand – DIN Form B. So, what exactly is DIN Form B, and how does it relate to thermocouple heads, transmitters and junction blocks?

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