Fluid-components-international ST98 Manual General Information User Manual download pdf

CHAPTER 1 - GENERAL INFORMATION FLUID COMPONENTS, INTL

Doc. No. 06EN003291 Rev. A

1 - 1

Model ST98 Flow Meter

1. General Information

Description

The model ST98 is a thermal mass flowmeter for air or gas measuring applications. The ST98 consists of a flow

element, a flow transmitter, and an enclosure. An in-line flow element is used for smaller diameter pipe or tubing

sizes and, for pipe sizes greater than 2-1/2 inches (40 mm bore), an insertion flow element is used. The flow

element’s process connections can be threaded or flanged.

The ST98 flow transmitter accepts AC or DC input power and the output signal can be set for either a standard

range current or voltage. A display is optional. An RS-232C serial I/O port provides setup, monitoring and

troubleshooting access using either FCI’s model FC88 Programmer or a PC-compatible computer.

The ST98 enclosures provide environmental protection for the flow transmitter. The flow transmitter can be

integrally mounted with the flow element or remotely separated from it. Hazardous location local and remote

enclosures are optional.

Theory of Operation

The flow element of the model ST98 uses the thermal dispersion operating principle: A low-powered heater

produces a temperature differential between two resistance temperature detectors (RTDs) by heating one of the

RTDs. Mass flow rate changes cool the heated RTD and cause a proportional change in the temperature

differential between the RTDs. The instrument’s flow transmitter converts the RTD temperature differential into a

scaled output signal and an optional indicated display value.

The signal from the unheated RTD is used to provide an indication of the air or gas temperature on the optional

display.

Insertion Sensing Element

The sensing element consists of two thermowells (hollow tubes) that when inserted into the flow process allows an

unimpeded flow inside the process line. A heated RTD is inserted into the top thermowell. A reference RTD

(with no heater) is inserted into the bottom thermowell. In order to correctly orient the sensing element a flow

arrow has been etched onto a machined flat portion of the sensing element. See Figure 1-1 for a view of the

sensing element.

The element is inserted into the process media through a hole drilled into the process line.

Figure 1-1 View of the Sensing Element

ARROW PARALLEL TO FLOW

ACTIVE RTD (HEATED)

REFERENCE RTD (NOT HEATED)

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Summary of Contents

Page 1 - 1. General Information

CHAPTER 1 - GENERAL INFORMATION FLUID COMPONENTS, INTLDoc. No. 06EN003291 Rev. A1 - 1Model ST98 Flow Meter1. General InformationDescriptionThe model

Page 2 - Instrument Configuration

FLUID COMPONENTS, INTL CHAPTER 1 - GENERAL INFORMATIONModel ST98 Flow Meter1 - 2Doc. No. 06EN003291 Rev. AFigure 1-2. Cut-Away View Of The In-Line F

Page 3 - Model ST98 Flow Meter

CHAPTER 1 - GENERAL INFORMATION FLUID COMPONENTS, INTLDoc. No. 06EN003291 Rev. A1 - 3Model ST98 Flow MeterTechnical Specifications• Process Connection

Page 4 - ST98 ABBREVIATED MENU

FLUID COMPONENTS, INTL CHAPTER 1 - GENERAL INFORMATIONModel ST98 Flow Meter1 - 4Doc. No. 06EN003291 Rev. AQuick Start Menu (Abbreviated)The following

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