Fluid Components International MT91 Manual General Information - Manual

Doc. No. 003185 Rev. B 1 - 1 Model MT91 Multipoint Flowmeter
CHAPTER 1 - GENERAL INFORMATION FLUID COMPONENTS INTL
1. General Information
Description
The MT91 is an air and gas mass multipoint flowmeter that incorporates a remote flow element connected to a
microprocessor control and display package (flow transmitter) designed to measure mass flow in ducts, stacks, or
places where irregular flow may reduce the accuracy of single point metering. The MT91 measures mass flow from
up to 16 different sensing points. An average of all individual flow signals produces an output signal representing
total mass flow. The MT91 can be factory calibrated to sense a range of mass flow from 0.25 SFPS to 150 SFPS in
air at standard temperature and pressure (70°F at 14.7 PSIA).
Flow Element
The flow element holds all of the individual sensing points. Each sensing point consists of two pairs of thermowells
of the same size and shape (see Figure 1-1). One thermowell pair contains a heater and an active Resistance
Temperature Detector (RTD). The second pair contains the reference RTD and a thermal mass equalizer.
Figure 1-1. Flow Element Cutaway View of One Sensing Point
Flow Transmitter
The flow transmitter assembly provides power for the flow element, measure the Temperature Differential ( D T)
between the active and reference sensors for each individual sensing point, and averages all flow signals to one
output signal. Available outputs options are field programmable to select 4-20 mA, 0-10 Vdc, 0-5 Vdc, digital, with
relay output signals. Three serial communication ports, EIA-232C (RS-232C), EIA-422 (RS-422), or EIA-485
(RS-485), are also field selectable and programmable for output signals. Parameters are programmable using the
keypad or serial communication interface. See Figure 1-2.
K e y b o a r d
Input
Display
O u t p u t
S e n s o r
Excitation
S e n s o r
Data
Acquisition
A n a l o g
Input
Serial
Interface
R S - 2 3 2 C
R S - 4 2 2
R S - 4 8 5
Analog Output
4 - 2 0 m A
0 - 1 0 V d c
1 - 5 V d c
Relay Output
P a r a m e t e r
A l a r m s
MT91 Microprocessor
Serial
E E P R O M
C 0 0 2 2 6 - 1
MT91 Transmitter Keypad and Display Package
Figure 1-2. Functional Block Diagram