We have HART field devices, but we only get the analog signal from the field! How should we upgrade the system to read the diagnostics? With PLC cards or a multiplexer or maybe a wireless adapter?
Ah, looks like you’ve started exploring your options. Good! You have many ways to improve your system, so you’ll need to decide by factoring the cost, structure, and service involved in HART each option.
First of all, you need to know the cost per point for each solution. I’ll give you an example. A new HART card for your programmable logic controller costs $8000. Because the card provides you 18 HART inputs, the cost per point will be the cost of the card divided by the number of inputs. In this case you’ll pay $ 444.44 per point plus the time to install the point and structure!
If you can upgrade the card, you might not have to pay for a new structure, depending on the system. Sometimes you need to change the whole system.
The multiplexer requires a new panel to translate the data before entering the control system, so you’ll have the cost of the panel, service to build the components inside the panel, installation, and start up!
The wireless adapter, on the other hand, doesn’t require installed structures. It can install directly into the transmitter. Although depending on the transmitter, you may need to turn off the transmitter during the adapter installation.
All these options will have different service needs. The PLC and multiplexer will need new panels, installation, start up and commissioning. The wireless solutions need installation, commissioning, and start up. Overall, you’ll spend less on service with the wireless.
You should do the same breakdown for all your options and analyze the pros and cons of each. Sometimes you may spend less but lose benefits you may want or need if you choose a cheaper solution.
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