Archive for category HART

Changing the COM port for a USB HART modem in Pactware

Written by: Dan Weise

I couldn’t communicate with a HART device. The configuration software I was using, Pactware, thought the USB HART modem was on COM 3, while Windows’ Device Manager showed it was actually on COM 6.

COM Port Post

COM Port Post 2

To change the COM port in Pactware to COM 6, I right clicked COM 3 and selected Parameter:

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Honeywell smart transmitter design makes communication card swap easy

It was bound to happen sooner or later.

I took a call from a customer who needed to replace a garden variety differential pressure transmitter… with one exception: He needed Honeywell’s DE digital protocol for communicating to his DCS. The DE protocol is still great, but since so many installations today use HART or Foundation Fieldbus, all of our in-stock pressure transmitters had a HART communication card – a critical mismatch to what the customer needed.

A year ago, we would have been stuck rush-ordering a unit from the factory, with all the attendant delays and expediting charges, because you couldn’t swap out a comms card without making the transmitter’s hazardous approval invalid.

What could we do?
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LUT400 universal 4-20mA analog output gets rid of the ground loop

The Problem
Before I talk about the value of a universal 4-20mA analog output on a level controller, let me explain why anyone would care. It’s all about ground loops.

Since the early days of electronic instrumentation, way back when, even before cell phones or PCs, instrument people struggled with ground loops that create an offset error, drive the signal off scale, or burn up an analog circuit.

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HART communications without busting the budget

The HART communication protocol has been firmly established as the standard means of configuring field instruments for some years.   But talking to a field instrument needs a communicator.

There are the handheld communicators, Rosemount’s  x75s and the “budget-priced” Meriam MFC 4150, but at a cost that’s more a capital appropriation than an MRO expense.  Even the Meriam, with a 3-year field device description subscription starts at more than $4000.

People continue to ask me if there isn’t a more budget conscious approach to HART configuration.

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Digital Communications Toolkit

We’ve gotten feedback from several people who have asked what I carry around to deal with serial or Ethernet communications issues.  So I dumped out my comm tool bag and here’s the list of all the stuff.

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February 2: A day to look back

Yesterday and today, people all over Chicago and the Midwest were looking at pictures from last year. We had 22″ of snowfall in one day. The roads were closed. The airports were closed. Even the Lesman offices were closed. And today’s weather forecast? 45°… in Chicago… in February.

This morning in Pennsylvania, a groundhog named Phil came out, looked back, and saw… his shadow.

All this looking back made me a little reflective myself. I’ve been writing this blog for about 6 months now. So I thought I’d take a minute and recap the articles people keep coming back to read:

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How does adding a 250-ohm resistor make HART work?

Sometimes there’s a problem getting a loop powered HART instrument to communicate when it’s on the benchtop, but it communicated fine when wired in the field.   Why is that? Read the rest of this entry »

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