Answer / carl_ellis

Given that 2 wire loop powered transmitters need approvals
for use in hazardous areas to be competitive, most, if not
all, transmitters regulate what changes can be made to
their products by limiting what spare parts or updates can
be made to an original product.

A hazardous area approval (FM, ATEX) is granted for the
transmitter as it is submitted to the approval agency.
Changes to the transmitter require re-approval with all the
associated costs of re-approving a device.

Changing the internal firmware or any of the internal
hardware would void the approval on the original device.
That could make the manufacturer liable in case of failure
of the instrument.

Firmware revisions are not offered for the base functions
of field transmitters.

An accessory item, like a digital display, that is not a
core element of the measuring and reporting function can
sometimes be swapped out with other units of different
firmware versions.

Sensor bodies for pressure transmitters and entire
electronic heads can be exchanged, or entire electronic
card assemblies can be exchanged, but firmware updates are
not available for devices that have agency approvals for
hazardous areas.

Software drivers for communications protocols change over
time and matching the firmware revision of a field
transmitter to its DD (Device Descriptor) or EDDL or DTM or
DOF file can be a challenge, but these are software files
used by communicators or PC/modem communication software.
The instrument manufacturer posts these kinds of files on
their web sites for download.

Carl Ellis
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