RIA15
HART
®
communication
Endress+Hauser 61
Unit code Description Display text
166 Normal cubic meters Nm3
167 Normal liters Nl
168 Normal cubic feet SCF
169 Parts per billion PPb
170 - 219 Unit Code Expansion Tables UC170 -
UC219
220 - 234 not defined UC220 -
UC234
235 Gallons per day gal/d
236 Hectoliters hl
237 Megapascals MPa
238 Inches of water at 4 °C inH2O
239 Millimeters of water 4 °C mmH2O
240 - 249 Manufacturer-specific UC240 -
UC249
250 Not used -----
251 None
252 Unknown UC252
253 Special UC253
15.5
HART
®
protocol connection types
The HART protocol can be used for point-to-point or multidrop connections:
Point-to-point (TYPICAL)
In point-to-point mode, the HART
®
master is connected with exactly one HART
®
slave.
A point-to-point connection should always be the preferred option where possible.
Multidrop (measurement not by current, slower)
In multidrop mode, several HART
®
devices are incorporated in a single current loop.
Analog signal transmission is disabled in this case and data and measured values are
exchanged exclusively via the HART
®
protocol. The current output of each connected
device is set to a fixed value of 4 mA and is only used to supply current to two-wire
devices.
Several sensors/actors can be connected in parallel to one wire pair in multidrop mode.
The master then differentiates between devices based on the configured addresses. Each
device must have a different address. If more than 7 sensors/actors are connected in
parallel an increased voltage drop occurs.
The loop must not include a mixture of devices with an active current output (e.g. four-
wire devices) and devices with a passive current output (e.g. two-wire devices).
The HART
®
protocol is immune to interference. This means that, during operation,
communication devices can be connected or removed without putting components of the
other devices at risk or interrupting their communication.
To Next Page
Loading...
