Dwyer PUX - Manual (Page 82)

11- 2
State Cause
Indication of measured
value is negative (-).
Measured value
fluctuated widely
though flow rate is
constant.
Measured value
remains the same
though flow rate is
changing.
Connect correctly.
Shift measurement location to
the site where 10D and 5D can
be secured on the upstream and
downstream sides.
Mount the instrument with a
clearance of 30D or more.
Extend response time through
damping setting.
11.3 Error in measured value
Remedy
• Connection between the main unit
and sensors (upstream sensor and
downstream sensor) is reverse.
• Fluid is actually flowing in the (-)
direction.
• Straight pipe portion is inadequate.
• A flow disturbing factor such as
pump or valve is provided in the
vicinity.
• Pulsation is occurring actually.
• Measured value is held because ultrasonic
wave cannot be propagated into a pipe.
1. Incomplete installation
• Piping specifications are wrong.
• Sensor is mounted at the welded
part.
• Sensor mounting dimension is
wrong.
• Grease application at sensor
mounting is incomplete.
• Sensor connector is not
connected completely.
• Pipe surface is contaminated.
2. Problem on pipe or fluid
• When V method is used, it should
be changed to Z method.
• When sensor extension cable is
used, it should be avoided.
• If error persists, check and
eliminate the true cause as
instructed below.
Fluid is not filled.
After check, separate the sensor
once. Apply the grease again
and remount the sensor with a
slight shift.
Find the location on the same
pipe line, where fluid is filled
up and move the sensors to that
location.
Mount the sensors at the lowest
location on pipe line.
BULLETIN F-68