Siemens LC 500, Sitrans instruction manual Safety Grounding, Example

Interconnection

Safety Grounding

The safety grounding requirements are determined by the application and the connected instruments. The SITRANS LC 500 transmitter does not have any special requirements due to the galvanic separation between the measurement section and the loop section.

Depending on the DCS characteristics, there are three possible grounding options:

•If the DCS measures the current through the loop compared to a common zero Volt point, do not ground the negative side of the current loop because measurement inputs can be short-circuited.

•If the DCS measures the current in the positive wire or connector, the negative side of the current loop can be grounded.

•If the DCS has galvanically separated inputs for each measurement channel the grounding method can be chosen as required.

In hazardous applications a Stahl-type barrier is required, and it is typically mounted on a DIN rail inside a customer-supplied enclosure located in the non-hazardous area.

Example 1

If no specific Ex conditions apply, the SITRANS LC 500 can be directly connected to the DCS. The supply voltage, however, should remain within the limits set by the SITRANS LC 500. Connecting a SITRANS LC 500 to a DCS does not influence that equipment. One of the connection cables can be grounded if desired.

	3,6 - 22 mA
	13 < Vsupp < 32 Vdc.	DCS APPARATUS
Type:

Ser.:

Date:

Rev.:

Tampering voids warranty

GND

COAX

Example 2

In the case of Intrinsically Safe applications, where the DCS equipment measures the current in the positive connection and the negative connection can be grounded, a barrier type as shown below is sufficient.

hazardous area

non-hazardous area

Type:

Ser.:

Date:

Rev.:

Tampering voids warranty

COAX GND

Stahl barrier: 9002/01-280-

110-00 (or equal)

3	277	110 mA	1
4	PA	28V PA	2

DCS APPARATUS

Rmeas

0 V

Page 30 SITRANS LC 500 – INSTRUCTION MANUAL 7ML19985GE01