Siemens SITRANS LR260 Operating Instructions Manual page 27

Passive Shunt Diode Barriers
Note: A well regulated supply voltage is required.
Manufacturer
MTL
MTL
Stahl
Stahl
How to select a passive barrier for SITRANS LR260
To make sure that the barrier safety description is suitable for the LR260 Intrinsically Safe
(IS) input parameters, carry out the following calculations:
Re-e = max. end-to-end resistance of the barrier
Rloop = loop resistance (total of cable resistance plus any additional series
resistance, for example, PLC inputs and/or displays)
Vbarrier = value of any non-linear voltage drops due to the barrier
1) Determine the value for Re-e from the data sheet.
2) Calculate the total value for Rloop.
3) Calculate Rworking = Re-e + Rloop.
4) Determine the value of Vbarrier from the barrier data sheet (for example, voltage
drops due to diodes).
5) Calculate Vworking = Vsupply – Vbarrier.
Use the values for Vworking and Rworking to confirm that operation is within the
shaded area of the graph
Active barriers (repeating barriers)
Manufacturer
MTL
MTL
Siemens
Stahl
MTL
MTL
7ML19985KE02 SITRANS LR260 (HART) – INSTRUCTION MANUAL
Part Number
787SP+ (Dual Channel)
7787P+ (Dual Channel)
9001/01-280-100-10 (Single Channel)
9002/01-280-110-10 (Dual Channel)
Startup Behavior
on page 101.
Part Number
706
7206
SITRANS I 7NG4122
9001/51-280-110-14
E02009
E02010
Page 21