DE Communications/Lighting Strikes

I am working with Honeywell Smart Line Transmitter STD700 Series

The transmitters connected to the DE stem cards are pressure units that are having issues. They are all newer model SmartLine series.

STD720 (DE)
STD740 (DE)

The transmitters are not damaged by the near lighting strikes causing this issues. The DE signal affected causes the DE stem card not see the input from transmitter intermittently which causes trip. The DE signal is either too noisy for DE stem card to recognize or DE is driven high or low outside of tolerance of stem card. Customer thinks that if stem card had longer threshold or delay in recognizing valid DE input this might help with the problem. We are adding LP terminal blocks now to existing transmitters to see if this helps in any way but customer wants to go down this path as well. Again – the existing SmartLine pressure transmitters that are communicating analog and not DE to this same TDC are not having any issues.

DE should be more robust than most other comm protocols because of its physical implementation - it modulates the 4-20mA signal between 4mA and 20mA for bit state changes. Given a current loop's inherent ability to work in noisy environments and with the very large amplitude change in current, the physical side of DE is known to be robust.

However, DE was originally developed by Yamatake (now Azbil) and licensed by Honeywell. The two once partnered quite closely but there's been a falling about in the recent past, and I'm speculating that DE's development is now in the hands of the Asian learn-as-you-go programmers.

There was at least one major upgrade to DE early on in after the Smartline introduction. There might have been more, I don't keep track.

But I'd put my money on a firmware issue, since the firmware development seems largely unsupervised, as evidenced by a constant flow of firmware updates for the Smartlines. (the old Beige ST3000's never had firmware updates, but that was a different era).

Honeywell has a kit called Anytime updater tool with a USB modem and a set of cables that connect to the Smartline modules. The most recent set of firmware files is almost a year old, dated June 2019, under the software tab at this URL:
https://www.honeywellprocess.com/en...nsmitters/smartline-st-700/Pages/default.aspx
at the bottom of the list.

You could try buying a replacement DE card (replaces in about 2 minutes with a phillips screwdriver) but if it comes from distributor stock, how old is the firmware? Maybe a distributor that has an updater kit will load the latest firmware onto the DE card.

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