Output (Hart) Transmitter Wiring; Communication Setup - ABB 266 DDS Operating Instruction

Pressure transmitters

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2 6 6 D D S H A R T | P R E S S U R E T R A N S M I T T E R S | O I/ 2 6 6 D D S - E N R E V. A

. . .5 Transmitter wiring

Analogue output (HART) transmitter wiring

Figure 16 - HART Transmitter connection scheme

HART hand-held communicator may be connected at any wiring termination point in the loop, providing the minimum resistance is

250 ohm. If this is less than 250 ohm, additional resistance should be added to allow communications. The handheld terminal is

connected between the resistor and transmitter, not between the resistor and power source.

Application

Transmitter operated outside the potentially explosive atmosphere

Transmitter operated inside the potentially explosive atmosphere

WARNING - RISK OF EXPLOSION

If, when using transmitters with type of protection "intrinsic safety", an ammeter is connected to the output circuit or a modem

is connected in parallel while there is a risk of explosion, the sums of the capacitances and inductances of all circuits, including

the transmitter (see EC-type-examination certificate) must be equal to or less than the permissible capacitances and

inductances of the intrinsically safe signal circuit (see EC-type-examination certificate for the power supply unit).

The transmitter can be operated via a HART modem, using a PC or laptop. The HART modem can be connected to the transmitter in

parallel at any point in the signal circuit. Communication between transmitter and modem occurs via FSK signals that are

superimposed on the analog 4 to 20 mA output signal. This modulation occurs without averaging, therefore does not affect the

measuring signal.

Communication between transmitter and PC or laptop is only possible if the signal circuit is set up as shown in the following

figure. The resistance between the connecting point for the FSK modem and the power supply must be at least 250 Ω (including

internal resistance of the power supply unit). If this value is not achieved within the context of normal installation, an additional

resistor must be used.

Permissible voltage range of power supply

Standard

from 10.5 to 42 V

from 10.5 to 30 V max (intrinsically safe)

from 10.5 to 42 V max (explosion proof)

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