Siemens Sitrans Manual De Usuario
7ML19985GE01
SITRANS LC 500 – INSTRUCTION MANUAL
Page 27
m
mmmm
Int
erc
onnect
ion
Protection for solid-state switch
•
For dc circuits: connect protection diodes in the the correct polarity across the relay
coil.
coil.
•
For ac circuits: connect a Voltage Dependent Resistor (VDR) or other ac compatible
component (such as zeners and protection diodes in combination) in the correct
polarity across the relay coil.
component (such as zeners and protection diodes in combination) in the correct
polarity across the relay coil.
Grounding instructions
Connect the housing and the process connection with either the stilling well
1
and/or tank
wall, using the ground lug on the housing.
Notes:
•
Since the measurement occurs between the Measurement and Ground
connections, it is important to have good, low-resistance, reliable connections in
this circuit.
connections, it is important to have good, low-resistance, reliable connections in
this circuit.
•
Use a ground connection wire with a sufficiently large diameter relative to its
length, and not less than 1 mm
length, and not less than 1 mm
2
.
•
The SITRANS LC 500 measurement circuit is completely isolated from the loop
circuitry: this allows either line of the loop circuit to be grounded if requirements
for Ex safety are followed and if the power supply voltage is less than 33 Vdc.
circuitry: this allows either line of the loop circuit to be grounded if requirements
for Ex safety are followed and if the power supply voltage is less than 33 Vdc.
1.
Where the stilling well is welded to the tank.
WARNING: When connecting the probe, do not leave moisture or metal scrap
(from the cable shielding, for example) inside the housing. This could interfere
with transmitter operation, or cause a short circuit.
(from the cable shielding, for example) inside the housing. This could interfere
with transmitter operation, or cause a short circuit.
Type:
Ser.:
Date:
Rev.:
Ser.:
Date:
Rev.:
Tampering voids warranty
instrument system
ground connection point
instrument system ground
(connected at factory)
label / protective seal
(DO NOT REMOVE)
ground lug