HART 7’s Biggest Benefit

Most people, in part because the marketing folks tell us so, believe that the addition of wireless to the HART standard is the most important part of the latest version. I beg to disagree.

HART has been becoming more fieldbus like with each new generation of the standard and this is certainly true with this latest edition. I think, the most significant addition to HART 7 is ‘report by exception’ as this means you no longer have to send a Command 3 or Command 48 from the host to the device on a regular basis to find out if anything is wrong because now the device can tell you. Talk about bandwidth savings. And at 1200 baud that IS significant. You no longer need to poll the device for it to be able to share a change in status with the host whether that host is your control system/DCS or an asset management system. Report by Exception is definitely useful for maintenance notifications or device failures as it makes predictive maintenance possible. Predictive maintenance has been shown to be 5x more cost effective than Preventative Maintenance so as added enticement there is even an economic carrot for this one.

Unfortunately, HART 7 devices are just being released to market, but over time just through regular maintenance practices as existing HART devices get replaced the capability will be huge.

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Comments

  • No. WirelessHART is definitely the most significant benefit from HART7. Wireless is the best thing since fieldbus. It’s a big milestone.

     

    In my personal opinion, for hardwired 4-20 mA devices, HART7 does not have major benefits over HART5. I’m not sure if report by exception will be used much for hardwired HART devices because it requires the burst mode which takes bandwidth, slowing down retrieval of valve signatures and echo curves etc. I believe that for hardwired HART systems will still use polling. Many things are optional. Therefore HART5 is find for hardwired devices.

     

    Report by exception works great for WirelessHART because it is much faster, 250 kbit/s. WirelessHART vibration transmitters and temperature transmitters etc. will do a lot for predictive maintenance.

    Cheers,

    Jonas

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