Siemens Sitrans LR250 Instruction Manual page 23

Passive Shunt Diode Barriers
A well regulated supply voltage is required.
Note:
Manufacturer
MTL
MTL
Stahl
Stahl
How to select a passive barrier for SITRANS LR 250
To make sure that the barrier safety description is suitable for the LR 250 Intrinsically Safe
(IS) input parameters, carry out the following calculations:
Re-e =
Rloop =
Vbarrier =
1. Determine the value for Re-e from the data sheet.
2. Calculate the total value for Rloop: by adding, for example, sense resistance,
displays, and/or PLC inputs.
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
Stahl
Pepperl+Fuchs
Pepperl+Fuchs
MTL
MTL
7ML19985JE01
Part Number
787SP+ (Dual Channel)
7787P+ (Dual Channel)
9001/01-280-100-10 (Single Channel)
9002/01-280-110-10 (Dual Channel)
max. end-to-end resistance of the barrier
loop resistance (total of cable resistance plus e.g. sense resistance,
displays, and/or PLC inputs)
value of any non-linear voltage drops due to the barrier
Loop Voltage versus Loop Resistance
Part Number
706
7206
9001/51-280-110-14
KSD2-CI-S-Ex
KFD2-STC3-Ex1
E02009 - verify
E02010
SITRANS LR250 (HART) – INSTRUCTION MANUAL
on page 114.
Page 23