Siemens sitrans PROBE LU - Condensed Status Setup

A5E32337695 SITRANS Probe LU (HART) – OPERATING INSTRUCTIONS Page 95
G: Hazardous Installation
Loop Voltage versus Loop Resistance
IS Safety Barrier Selection
Selecting a suitable barrier or power supply requires knowledge about Intrinsic Safety
and the application. It is the responsibility of the installer to ensure that the intrinsically
safe installation complies with both the apparatus approval requirements and the
relevant national code of practice.
How to select a passive barrier for SITRANS Probe LU
1. Make sure that the barrier safety description is suitable for the SITRANS Probe LU
Intrinsically Safe (IS) input parameters.
2. Determine the maximum end-to-end resistance of the barrier (Re-e) from the data
sheet.
3. Determine other loop resistance (Rloop): for example, sense resistance, displays,
and/or PLC inputs.
4. Calculate Rworking = Re-e + Rloop.
Power Supply Requirements
0
100
200
300
400
500
600
700
800
900
1000
10.00 15.00 20.00 25.00 30.00
Loop Voltage-V
L
(Source voltage)
Loop Resistance - R
L
RL=44.6*VL - 493.4
RL=272.7*VL - 4554.1
(16.7v, 0 ohms)
(17.8v, 300 ohms)
(30.0v,845 ohms)
ALLOWABLE OPERATING
AREA