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.
There is: Pactware software, a Windows application that can talk HART to field instruments. And even better: It’s a free download with NO licensing fee.
So, before you get started, here’s what you need to make it work
- The software. I use the Krohne version. It runs in both XP and Windows 7 (32-bit). http://www.pactware.com/en/products/pactware.html
- A HART modem, to connect your PC to the field device. I use the Viator USB HART modem from MACTek. It runs about $500.
- Now, you need to download two more file types: The first is a basic HART driver (called a DTM) that enables and manages HART communications through a HART modem. http://www.codewrights.biz/
- Next, you need a driver (DTM file) for each model field instrument. The instrument manufacturer is responsible for providing the DTMs. Some do, and some don’t. It depends. You can ask the manufacturer whether a DTM is available, and where to download it.
HART needs at least 230 ohms of loop resistance to operate, so when trying to connect with an instrument on the shop bench, be sure to put a resistor in the loop, because it won’t communicate with just an instrument and a power supply.
Obviously, a laptop with a HART modem is not useable in a hazardous area, but the nature of HART allows it to communicate without being directly connected to the instrument. It works fine connected at the marshalling panel, control panel, or wherever wiring terminations for loop can be found.
The power of PC offers two key advantages over a handheld.
- The configuration parameters are listed in an overview form:
- By running on a PC, the graphics can offer more than a handheld, like echo profiles for non-contact radar or ultrasonic level instruments:
So, if you think a HART handheld is a budget-buster in your world, consider Pactware and a HART modem as your HART communications tool.
Learn more about HART Handheld Communicators and Modems at Lesman.com