Operation; General Information; Measuring Principle - Siemens sitrans LR 400 Instruction Manual And Users Manual

Operation

General Information

You can operate the SITRANS LR 400 with:
• Hand-held infrared programmer
• HART Communicator or PROFIBUS PA
• PC/Laptop and SIMATIC PDM software (recommended)
Notes:
• The SITRANS LR 400 can be operated and programmed most comfortably
with the SIMATIC PDM software. This software gives you the added
possibility of saving and archiving your application-specific parameters and
copying them back into the device if necessary.
• It is best to perform the operations described in the following sections
directly on the device to familiarize yourself with the operation.

Measuring Principle

The SITRANS LR 400 operates according to the FMCW (Frequency Modulated Continuous
Wave) method. Its antenna sends microwaves to the surface of the measuring medium.
The wave frequency is modulated continuously (see Determining the Differential
Frequency on page 25). A receiver registers the reflection at the surface of the measuring
medium and links it with the simultaneously radiated signal.
The propagation speed of microwaves in gases corresponds to the speed of light. The
distance d is proportional to the propagation time t:
d= distance, t = measured time, c = speed of light
7ML19985FH04
SI TR A N S LR 4 0 0
d
c t ⋅
--------
d =
2
SITRANS LR 400 – INSTRUCTION MANUAL Page 24