Installation & Operation 1-1
August 2008
Introduction The PT878 is a transit-time flowmeter that combines all the features
of a full-size flowmeter with the advantages of a portable instrument:
• measure the flow rate of acoustically-conductive single-phase
fluids
• measure flow velocities from ±0.03 to ±12 m/sec
• energy flow rate may be calculated for water, glycol, and water/
glycol mixtures
• one linear 0/4-20 mA analog output
• two 4-20 mA analog inputs
• runs on rechargeable or alkaline batteries for up to 10 hours
• LCD display for measurements in numeric and graphical format
• store site data in files
• log over 100,000 flow data points internally
• communicate with a PC via an infrared port
• context-sensitive on-line help
• uses all standard GE Sensing transducers
The Flowcell In addition to the PT878, a complete flowmeter system includes a
flowcell. The flowcell is that part of the system that uses ultrasonic
pulses to interrogate the flow. It consists of:
• Flowcell Pipe - The flowcell can either be created in the existing
piping (for example, by inserting wetted transducers into the pipe,
or clamping non-wetted transducers onto the pipe), or inserted as a
substitute pipe section (spoolpiece). The flowcell must provide
mechanical support for the transducers and assure stable fluid
conditions for accurate flow measurement.
• Transducers - The transducers convert electrical energy into
ultrasonic pulses when in a transmit cycle, and convert the
ultrasonic pulses back to electrical energy when in a receive cycle.
In the PT878 system, each transducer acts as both a receiver and
transmitter, since a series of ultrasonic pulses are alternately sent
upstream and then downstream through the flowcell.
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