GE General Electric Oxygen Equipment PT878 用户手册

Chapter 1. Features and Capabilities

Transport® Model PT878 Portable Liquid Flowmeter User’s Manual

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The PT878 consists of circuits that generate, receive, and measure the travel 
time of the ultrasonic pulses. It also contains a microcomputer that controls 
operation and calculates flow measurement parameters. Specific circuits 
function as follows:

 TRANSMIT SIGNAL GENERATOR - The transmit signal generator, 
under control of the microcomputer and timing circuit, synthesizes the 
signal that drives the transmitter.

 TRANSMITTER - The transmitter amplifies the signals from the 
transmit signal generator to a signal that drives the transmit transducer.

 RECEIVER - The receiver amplifies the received signals to a level 
suitable for the data acquisition circuitry.

 DATA ACQUISITION - The data acquisition circuitry digitizes the 
received signal and stores it in a buffer for processing by the 
microcomputer.

 TIMING CIRCUIT - The timing circuit generates the transmitter 
frequency, receive window, controls the data acquisition circuit and the 
direction of the transmission.

 MICROCOMPUTER - The microcomputer controls the PT878 
flowmeter’s operation and calculates flow measurements derived from 
the transmitted and digitized received signals. Also, the microcomputer 
continually checks for faults and allows the use of built-in diagnostics for 
troubleshooting.

 INPUT/OUTPUT - The input/output circuitry allows the flowmeter to 
indicate the measured flow with the 0/4-20 mA current loop, and to 
output to a printer or other remote device. The digital output supports 
frequency or pulse output, as well as use as a gate input; it can also act as 
a test point for triggering an oscilloscope from the transmit or receive 
window.