Posts Tagged transmitter

Is it time to switch switches?

Eight problems with outdated, electromechanical switches and eight solutions that will come with a digital upgrade to your plant.

Operational VisibilityUE Electric Safety Transmitter

The Problem: Unless tested on a regular basis, there is no way to determine when a problem exists. With mechanical switches, the only way to diagnose a problem is to remove the switch, leaving the control or safety function
unprotected.

Solution: Newer digital switches have an LCD screen that shows local process variable measurements and integrated internal diagnostics directly on the screen. You can easily monitor the health of the device at a glance, without having to remove the switch from operation.

Adjustability

The Problem: Mechanical switches require careful adjustments for reaching desired setpoints. Additionally, once these adjustments are made, settings

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Minimizing shift on a draft range differential pressure transmitter

A while ago, I got a call from a customer who was having trouble with a differential pressure transmitter. He was using a draft range DP transmitter to measure the pressure in a combustion chamber, so it could be controlled with a damper. He had one port connected to the combustion chamber with impulse tubing, and the other (low side) was left open to the atmosphere.

He’d noticed that when a fork truck or other vehicle sped past the furnace – the transmitter was mounted next to a traffic lane — it cause the furnace pressure to momentarily dip downward, and cause the damper to oscillate.

He figured out that the air movement provided by the passing vehicle was creating a momentary pressure pulse on the low side port. These air movements were creating difficulty in maintaining furnace pressure.

So, he asked me, “How can we dampen the effect of the momentary pressure pulse?”

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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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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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