Posts Tagged transmitter
Eight problems with outdated, electromechanical switches and eight solutions that will come with a digital upgrade to your plant.
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
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.
The Problem: Mechanical switches require careful adjustments for reaching desired setpoints. Additionally, once these adjustments are made, settings
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?”
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?
Read the rest of this entry »
Ran into a situation last week that taught me an important lesson.
A customer took a tank out of service for major repairs, so they moved the Siemens radar level transmitter to a different tank. Even though the radar unit performed flawlessly on the first tank, they ran into difficulty getting the correct level readout in its new installation.
The mechanical guy had moved and remounted the transmitter. The I&E tech had wired it correctly, and then did a master reset before starting a fresh configuration. After going through the configuration, he couldn’t get a valid level readings in the upper fourth of the tank level.
The second tank was near its full level and the technician (properly) wanted to wait to do an Auto-Learn scan until the tank level approached empty. In the meantime, we were all scratching our heads trying to figure out why the upper level readings were not correct.
In frustration, I finally resorted to pulling out a manual . . . Read the rest of this entry »
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?