•
Output configuration 2R: power, RS-485, fault relay (N.O.), auxiliary relay
(N.O.), alarm relay (N.O.)
Electrical
outputs
•
Dry contact relays
Table A-3: Contact Ratings
Relay name
Type
Normal position
Maximum
ratings
Alarm
SPDT
N.O., N.C.
2 A at 30 Vdc
Auxiliary
SPST
N.O.
2 A at 30 Vdc
Fault (see notes 1
and 2)
SPST
N.C. or N.O.
2 A at 30 Vdc
1. The fault relay (in output configurations 1A, 2A, and 1R) is
normally energized closed during normal operation of the
detector. The relay is de-energized open if a fault condition or low
voltage situation occurs.
2. In output configurations 3A and 2R, the relay is normally energized
open during normal operation of the detector. The relay is de-
energized closed contact if a fault condition or low voltage
situation occurs.
•
0-20 mA current output: The 0-20 mA can be Sink or Source according to
the output configuration (see
General instructions for electrical wiring
The maximum permitted load resistance is 600 Ω.
Table A-4: 20 mA Current Output
State
Output
Fault
0 + 1 mA
Built-in test (BIT) fault
2 mA ± 10%
Normal
4 mA ± 10%
Warning
16 mA ± 5%
Alarm
20 mA ± 5%
•
HART protocol: The HART protocol is a digital communication signal at a
low level on top of the 0-20mA. This is a bi-directional field
communication protocol used to communicate between intelligent field
instruments and the host system. HART is available in output
configurations 1A, 2A, and 3A.
Through the HART protocol, the detector can:
—
Display setup.
—
Reconfigure the setup.
—
Display detector status and definition.
Reference Manual
Specifications and reference data
00809-0100-4976
June 2021
Rosemount 975HR
53
Legacy
