Blogging team for Dan's Tips, the education and tech tips blog for Lesman Instrument Company
More and more people are using Modbus to get data from their instruments and controllers back into their control systems for reporting, alarming and troubleshooting.
And while I can’t be there to help you set up your Modbus master, I can give you 13 rules and some general practice advice for communicating to any Modbus RTU device.
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 »
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 »