0415925-0322 Rev C
Solids Flow Detect Model FD-2000
Solids Flow Detect Model FD-2000
The model FD-2000 solids ow detector is an industrial instrument that senses ow or no-ow condi-
tions of solids and powders in pneumatic pipelines, gravity chutes and feeders. It uses microwave
Doppler technology to provide highly sensitive motion detection. The sensor is completely non-intru-
sive, avoiding contact with the ow stream and associated wear problems.
The FD-2000 is a single piece system that contains the sensing element, the power and output con-
nections and user adjustment controls. It provides both a relay output and current output for indica-
tion of ow or no-ow. Both normally closed and normally open contacts are available at the relay
output.
The FD-2000 sensor unit emits a low power microwave signal toward the material being monitored.
Part of this signal is reected off the material back to the transducer of the FD-2000. This reected
signal combines with the emitted signal to produce a beat frequency, which is the difference in fre-
quency between the two signals. If the material being monitored is not moving, the reected signal
will be the same frequency as the emitted signal and there will be no beat frequency produced.
However, if the material is moving, the reected signal will be shifted in frequency and a difference
or beat frequency will be produced. This shift in frequency is called the Doppler Effect. The presence
or absence of this beat frequency is sensed by the FD-2000 to detect a ow or no ow condition.
Microwaves are extremely high frequency radio waves and as such pass through non-metallic mate-
rials with negligible attenuation. This means that the FD-2000 can see through a plastic pipe, a glass
process seal or the wall of a wooden chute to detect the motion of material inside. This also means
that the FD-2000 can look all the way through a plastic pipe or wooden chute and see a person
walking on the opposite side. Therefore, in some installations where this situation may occur, a me-
tallic material will need to be placed on the opposite side of the pipe or chute to prevent the FD-2000
from seeing objects on the other side. Adjusting the sensitivity of the FD-2000 to a lower setting may
eliminate the sensing of moving objects on the other side of a nonmetallic pipe or chute.
Location and Mounting
The FD-2000 is mounted at the process site where the movement of material is to be monitored.
Often this will be on the side of a chute or ow pipe where access by personnel is difcult or limited.
When selecting a location, attention should be given to the temperature limits of the sensor to make
sure they are not exceeded. And, although the unit is equipped with a lter to reduce the effects of
mounting vibrations, it should be mounted where it will not experience excessive vibration as this
can be detected as motion and give a false indication of ow.
The sensor best detects movement of material moving directly toward or away from the unit. How-
ever, mounting the unit perpendicular to ow usually works because there is adequate uctuation
of material as it ows past to allow detection. In some cases where the material is very light and dif-
cult to detect, it may be necessary to mount the unit at some angle off perpendicular to the ow. An
angle of 20 to 30 degrees from perpendicular is usually sufcient. Refer to Figure 1 for examples.
INTRODUCTION/DESCRIPTION
