Fluid Components International GF90_GF92 - Manual (Page 5)

Doc. No. 06EN003229 Rev. H 1 GF Series Flow Meter Models GF90/GF92
FLUID COMPONENTS INTERNATIONAL LLC http://www.fluidcomponents.com
This document describes the procedures required to install, operate, maintain, and troubleshoot the
Model GF90 and GF92 Flowmeters. There are a wide range of possible configurations and information
related to the optional features. The flowmeter is composed of a remote thermal dispersion sensing
device (flow element) interconnected to a microprocessor-based electronics control and display package
(flow transmitter). The flow element can be attached directly to the flow transmitter (local instrument)
or it can be connected to the flow transmitter with a cable of up to 1000 feet or 300 meters (remote
instrument).
The instrument is designed to operate in gaseous mass flow metering environments. The flowmeter is
factory calibrated to handle a range of flows.
The flow element consists of 4 thermowells. The thermowells are hollow metal tubes that are braised
together to make 2 pairs of thermowells. One thermowell pair contains the active Resistance
Temperature Detector (RTD) and a heater. The other thermowell pair contains the reference RTD and
an empty thermowell for thermal mass equalization. Figure 1 shows the flow element.
The other component of the flowmeter is the flow transmitter. The basic functions of the flow
transmitter are to provide power to the flow element, measure the Differential Temperature (
∆ T)
between the two RTDs as a function of resistance, amplify and linearize the Differential Resistance
(
∆ R) measurement of the flow element input signal and to provide an output signal.
This output signal is calibrated to the flow rate as a function of velocity, standard volume or mass flow.
To perform these functions, microprocessor-based electronic circuitry is employed to acquire the analog
voltage signals from the RTDs, digitize and interpret the information.
The microprocessor-based electronics provides maximum flexibility and ease of operation with a menu-
driven selection of control, monitoring, display and driver options.
Description
1. General Information
Flow Element
Flow
Transmitter
Figure 1. Cut-Away View of the Flow Element