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15
LTDR TRANSMITTER
The LTDR level transmitter uses TDR (Time Domain Reflectometry) technology to measure
level.
This technology is based on the emission of electromagnetic pulses of low energy and high
frequency, generated by an electronic circuit. The impulses are propagated along a probe
immersed in a liquid.
When these impulses reach the surface of the liquid, part of the impulse energy is reflected
and returns to the electronic circuit, which calculates the fluid level from the time difference
between the sent and received impulses.
The transmitter analyses the signal and converts it into a continuous and proportional to the
level measurement through its analog output, or into a programmable switching signal at a
specific level point.
TDR sensors are also known as guided radar devices.
The information related to these transmitters can be found in its specific manual.
16
MAINTENANCE
16.1
Series LT
No special maintenance is required.
16.2
AMD limit switch maintenance
16.2.1 Electrical verification
Check that the voltage at the terminals + and - is over 7.5 V when the vane is in the slot.
Connect a multimeter with the scale in DC mA, in series with the terminal +.
Verify that the current is less than 1 mA when the vane is inside the slot and more than 3 mA
when the vane is outside the slot.
If a NAMUR amplifier is not available, the verification can be done with the following circuit
diagram:
Without the sensor, the operation of the amplifier can be checked by using the following
circuit diagram:
32
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