FMA 3200/3200ST/3400/3400ST Series
Thermal Mass Flow Controllers
READ THIS MANUAL COMPLETELY BEFORE ATTEMPTING TO CONNECT OR
OPERATE YOUR FLOW SENSOR. FAILURE TO DO SO MAY RESULT IN INJURY
TO YOU OR DAMAGE TO THE FLOW CONTROLLER.
TABLE OF CONTENTS
A. Introduction .............................................................................................4
1. Unpacking...........................................................................................4
2. Product Overview And Principle Of Operation..........................................4
B. Installation...............................................................................................5
1. General Considerations.........................................................................5
2. Mounting The flow controller ...............................................................7
3. Tubing Connections..............................................................................7
5. Electrical Connections ...........................................................................8
a) Overview ....................................................................................8
b) Connecting The 6 Pin Mini Din Connector............................................9
c) Connecting The 6 Pin Mini Din Connector & FMA 3000C Cable ........... 10
d) Connections For The 9 Pin D Sub Connector ......................................11
e) Connections For The 15 Pin D Sub Connector.....................................12
f) Using a 0-5VDC Output / Input Power Adapter Package....................... 13
C. Operation .............................................................................................14
1. Warm-Up .......................................................................................... 14
2. Verification Of Zero ............................................................................14
3. Flow Readings....................................................................................14
4. Changing The Flow Rate Set-Point (Using An External Voltage Source) ....... 15
5. Changing The Flow Rate Set-Point – FMA3400 / 3400ST Only.................16
6. Power Save Mode............................................................................... 16
7. Zero Adjustments................................................................................17
8. Recalibration...................................................................................... 17
9. Changing The Calibration Gas – FMA3400 / 3400ST Only.....................17
D. Maintenance And Product Care................................................................ 18
1. General............................................................................................. 18
2. Returning Units For Repair Or Recalibration............................................18
E. Specifications......................................................................................... 19
F. Dimensions............................................................................................20
G. Gas K Factors ........................................................................................22
H. Trouble Shooting Guide .......................................................................... 23
M-4271/0707, pg. 3 of 26
A.
Introduction
1. Unpacking
All units are suitably packaged to prevent damage during shipping. If
external damage is noted upon receipt of the package, please contact
Omega Engineering immediately.
Open the package from the top, taking care not to cut too deeply into the
package. Remove all the documentation and contents. Take care to
remove all the items and check them against the packing slip. The
products should also be checked for any concealed shipping damage. If
any shortages or damage is noted, please contact Omega Engineering to
resolve the problem.
Typical Contents of Box: Controller, Calibration Certificate & Manual
FMA 3200/3200ST shown; FMA 3400/3400ST have an integrated display.
Caution: Take care not to
installation section of this manual before providing power or
tubing connections to the unit. Any damage caused by improper
installation or careless handling will not be repaired under
warranty (see limited warranty on page 25 for more details).
2. Product Overview and Principle of Operation
The FMA 3200/3400 Series Mass Flow Controllers from Omega
Engineering
any clean, dry gas as low as 0-20 sccm or as high as 0-10 l/min.
Repeatable results are achieved using a patented thermal mass flow
are capable of measuring and controlling the flow of virtually
drop
your controller. Read the
M-4271/0707, pg. 4 of 26
sensor design. This proven design minimizes zero drift while maintaining
fast response and linear outputs with virtually no maintenance.
The FMA 3200/3400 Series
utilizes thermal flow sensing
technology. A portion of the
gas flowing through the unit is
redirected into a small sensor
tube. This tube has two coils
on the outside. The first coil
introduces a small amount of
heat into the gas stream. As
the gas passes through the
tube heat is transferred from
one coil to the other. The flow
rate is proportional to the
amount of heat transfer. Smart
electronics analyze the amount
of temperature change in the
second coil and provide a
linearized analog output. A patented system insures that the zero remains
stable and the sensor is extremely repeatable.
Flow in the FMA 3200/3400 Series is controlled by a proportional solenoid
valve with active servo electronics. The flow measurement signal is
analyzed by micro-processor controlled electronics and compared to a setpoint. Adjustments are then made to the valve in order to achieve the
required flow rate. The set point can be either externally input via a 05VDC signal or in the case of the FMA 3400/3400ST Series it can be input
manually on the unit.
The output of the thermal mass flow sensor is directly related to the
specific heat characteristic of the gas being measured. A sensor is
calibrated for one gas but may be used with other gases by applying a
correction factor to the output. The calibration gas for each specific flow
controller is detailed on the product label.
B.
Installation
Caution: Do not exceed the pressure, temperature or power
operating ranges detailed in the SPECIFICATIONS section of this
manual. Omega Engineering shall not be liable for any damage
or injury caused by incorrect operation of their products.
1. General Considerations
It is recommended that a safety shut-off valve be installed upstream
(before) of the controller.
All wetted parts should be checked for compatibility with the gas to be
used. If there are any incompatibilities eg. highly corrosive gas, then the
M-4271/0707, pg. 5 of 26
unit may be damaged or fail prematurely. Such damage will not be
repaired under warranty.
Units should be installed in a clean, dry environment with an ambient
temperature that is as stable as possible. Avoid areas with strong magnetic
fields, strong air flows or excessive vibration.
In order to operate the differential pressure across the controller should be
in the range 15-45psid (1-3 bar). For optimum performance a differential
pressure of 25psid is recommended.
For Example, consider the following system:
The differential pressure across the flow controller in this system would be
100 psi – 14 psi = 86 psid. Consequently the flow controller would NOT be
able to control flow. For the unit to operate at optimum performance the
supply pressure from the gas cylinder would need to be lowered to 39 psig
to give 39 psi -14 psi = 25 psid.
M-4271/0707, pg. 6 of 26
2. Mounting the Flow Controller.
The FMA 3200/3400 Series controllers have no particular orientation or
installation requirements so may be mounted in any convenient position.
It is recommended that units be fixed to a suitable substrate using the two
4-40 mounting holes provided.
Mounting View from Bottom
(mounting hardware not included with sensor)
3. Tubing Connections
All tubing must be clean, dry and purged with clean dry air before
installation of the FLO-CONTROLLER
If the gas to be used may contain particles then a filter (20 microns or
less) should be installed upstream of (before) the unit.
When connecting the sensor to the tubing, take care not to over-tighten
the fittings or leaking may occur.
Caution: Only use the fittings factory installed on the unit. If
the fittings are removed the calibration of the unit may be
effected and leaking may occur. If different fittings are required
please contact the Omega Engineering Customer Service
Department for assistance.
®
.
M-4271/0707, pg. 7 of 26
4. Electrical Con ne ctions
Caution: Incorrect wiring may cause severe damage to the unit.
Applying an AC voltage (115VAC or 230VAC) directly to the unit
will cause damage. Read the following instructions carefully
before making any connections.
a) Overview
The FMA 3200/3400 Series provides a 0-5VDC analog output proportional
to the flow rate. This output may be connected to a display, data
acquisition system or voltmeter with an impedance of greater than 2.5 kΩ
(kilo ohms).
The flow controller needs to be supplied with a 0-5 VDC set point signal to
enable control. On the FMA 3400/3400ST Series this may be generated
internally by altering the set-point potentiometer on the front panel of the
unit.
A stable D.C. power supply is required to operate the unit. The voltage
and current requirements depend on the configuration of the unit. Full
details may be found in the Specification section of this manual.
Connecting wires should be as short as possible to avoid voltage drops.
Twisted conductor cable should be used if the length of the wiring is to be
longer than 2 meters.
Units are supplied with either a 6 pin mini DIN type connector (requires
mating cable assembly), a 9 Pin D Sub connector or 15 Pin D Sub
connector.
Caution: Cutting off the integrated connectors on the unit IS
NOT RECOMMENDED and will void the product warranty. Mating
cables should be ordered along with each unit.
Electrical connections to the units are made as detailed in the following
sections.
M-4271/0707, pg. 8 of 26
b) Connecting The 6 Pin Mini Din Connector
Using a suitable mating connector the pins of the integrated connector
should be wired as follows:
Connecting To The Integrated 6 Pin Connector
Pin Out of Integrated
Connector
Pin 2 should be connected to the Positive of the power source.
Pin 6 should be connected to the Negative (Ground) of the power source.
Pin 3 provides the signal output and should be connected to the positive
terminal of the display, data acquisition system or voltmeter.
Pin 1 is the signal negative (ground) and should be connected to the
negative (Ground) terminal of the display, data acquisition system or
voltmeter.
Pin 4 provides the input signal and should be connected to the positive
terminal of the voltage source. The (0-5VDC) voltage control signal should
be supplied from a low impedance source.
Pin 5 is the input signal negative (ground) and should be connected to
the negative (Ground) terminal of the voltage source.
Caution: Avoid high voltage static discharges to the input signal
connection. Do not short the input/output signal wires or allow
them to contact the power wires at any time. DAMAGE WILL
RESULT!
M-4271/0707, pg. 9 of 26
c) Connecting The 6 Pin Mini Din Connector & FMA 3000C Cable
The two mating connectors should be pushed together and the pigtail
leads wired as follows:
Connecting To The Integrated 6 Pin Connector Using A FMA 3000C Cable
The RED wire should be connected to the Positive of the power source.
The BLACK wire should be connected to the Negative (Ground) of the
power source.
The ORANGE wire provides the signal output and should be connected to
the positive terminal of the display, data acquisition system or voltmeter.
The BROWN wire is the signal negative (ground) and should be
connected to the negative (Ground) terminal of the display, data
acquisition system or voltmeter.
The YELLOW wire provides the input signal and should be connected to
the positive terminal of the voltage source. The (0-5VDC) voltage control
signal should be supplied from a low impedance source.
The GREEN wire is the input signal negative (ground) and should be
connected to the negative (Ground) terminal of the voltage source.
The wire colors above describe the pigtail leads of the FMA 3000C cable
assembly and may not correspond with the internal wiring of your flow
sensor.
Caution: Avoid high voltage static discharges to the input signal
connection. Do not short the input/output signal wires or allow
them to contact the power wires at any time. DAMAGE WILL
RESULT!
M-4271/0707, pg. 10 of 26
d) Connections For The 9 Pin D Sub Connector
Using a suitable mating connector the pins of the integrated connector
should be wired as follows:
Connecting To The Integrated 9 Pin Connector
Pin Out of Integrated
Connector
PIN 3 should be connected to the Positive of the power source.
PIN 4 should be connected to the Negative ( Ground ) of the power
source.
PIN 2 provides the signal output and should be connected to the positive
terminal of the display, data acquisition system or voltmeter.
PIN 8 is the signal negative (ground) and should be connected to the
negative (Ground) terminal of the display, data acquisition system or
voltmeter.
Pin 6 is the input signal and should be connected to the positive terminal
of the voltage source. The (0-5VDC) voltage control signal should be
supplied from a low impedance source.
Pin 7 is the input signal negative (ground) and should be connected to
the negative (Ground) terminal of the voltage source.
Pins 1, 5, and 9 are not used.
Caution: Avoid high voltage static discharges to the input signal
connection. Do not short the input/output signal pins or allow
them to contact the power connections at any time. DAMAGE
WILL RESULT!
M-4271/0707, pg. 11 of 26
e) Connections For The 15 D Sub Conne c tor
Using a suitable mating connector the pins of the integrated connector
should be wired as follows:
Connecting To The Integrated 15 Pin Connector
Pin Out of Integrated
Connector
PIN 7 should be connected to the Positive of the power source.
PIN 5 should be connected to the Negative ( Ground ) of the power
source.
PIN 2 provides the signal output and should be connected to the positive
terminal of the display, data acquisition system or voltmeter.
PIN 10 is the signal negative (ground) and should be connected to the
negative (Ground) terminal of the display, data acquisition system or
voltmeter.
Pin 8 is the input signal and should be connected to the positive terminal
of the voltage source. The (0-5VDC) voltage control signal should be
supplied from a low impedance source.
Pin 1 is the input signal negative (ground) and should be connected to
the negative (Ground) terminal of the voltage source.
Pins 3, 4, 6, 9, 11, 12, 13, 14 and 15 are not used.
Caution: Avoid high voltage static discharges to the input signal
connection. Do not short the output signal pins or allow them to
contact the power connections at any time. DAMAGE WILL
RESULT!
M-4271/0707, pg. 12 of 26
f) Using a 0-5VDC Input / Output Power Adapter Package.
An optional 0-5VDC Input / Output Power Adapter Package is available for
use with the FMA 3200/3400 Series. This consists of a power source
(115VAC or 230VAC), a connection hub and two cable assemblies with pigtail (soldered wire) ends. This should be assembled as shown in the
following diagram.
Assembling a FMA 3215PW Power Adapter Package
(the FMA 3223PW Power Adapter Package is similar)
The RED connector should be inserted in the RED socket on the
connection hub. The WHITE connector should be inserted in the WHITE
socket on the connection hub.
The cable with a RED connector provides the input signal. The RED wire
of this cable should be connected to the positive terminal of the voltage
source. The (0-5VDC) voltage control signal should be supplied from a low
impedance source. The bare wire of this cable assembly is the input
signal negative (ground) and should be connected to the negative
(Ground) terminal of the voltage source.
The cable with a WHITE connector provides the signal output. The
WHITE wire should be connected to the positive terminal of the display,
data acquisition system or voltmeter with an impedance of greater than
2.5 kΩ (kilo ohms). The bare wire of this cable assembly is the signal
negative (ground) and should be connected to the negative (Ground)
terminal of the display, data acquisition system or voltmeter.
Caution: Avoid high voltage static discharges to the input signal
connection. Do not short the output signal wires or allow them to
contact the power wires at any time. DAMAGE WILL RESULT!
M-4271/0707, pg. 13 of 26
C.
Operation
1. Warm Up
Before applying power to the unit check all tubing and electrical
connections. Once correct installation is verified switch on the power. The
unit should then be allowed to warm up for 5 minutes before gas pressure
is applied.
2. Verificat ion o f Ze ro
Flow through the unit should be stopped by sealing or capping the inlet of
the controller. It is not adequate to only stop flow by turning off the gas
supply or closing a valve as there may be a leak in the system. This would
give a false reading.
After 5 minutes, the zero should be stable when there is no flow through
the unit. If after 10-15 minutes the output is still not zero volts (within
±0.05 volts) the unit should be adjusted as detailed in section C part 6.
It should be noted that power supply voltage variations and changes in
ambient temperature can have an effect on zero readings.
3. Flow Readin gs
Each controller is factory calibrated for a specific flow range and gas (or
gas mixture). The calibration gas and flow range are shown on the unit’s
label and calibration certificate.
By monitoring the voltage output signal it is possible to determine the flow
rate of the gas. Units are configured so that an output signal of 5.0VDC is
provided when the maximum flow (i.e. Full Scale flow) is passing through
the unit. The output signal is linear and scaleable enabling calculation of
flow rates with in the sensor’s range. For example:
For a flow range of 0-500sccm:
At 500sccm the output signal would be 5VDC
If the output signal were 3.5VDC then the flow rate would be:
500 ÷ 5 × 3.5 = 350sccm
If the maximum flow rate is exceeded non-linear and inaccurate readings
will result.
Units may be used for gases other than the calibration gas. In this case a
“K Factor” would need to be applied and a corrected value calculated using
the following formula:
M-4271/0707, pg. 14 of 26
Q
/ Q2 = K1 / K2
1
Q1 is the flow rate of the new gas
Q
is the flow rate of the original calibration gas
2
is the K factor of the new gas
K
1
K
is the K factor of the original calibration gas
2
= (K1 / K2) Q2
Q
1
If K
is larger than K1 then linear results will only be achieved if the unit
2
does not exceed 5(K
Example 1
For a 0-200sccm unit calibrated for air the flow at 5.0VDC would be
200sccm. The K factor for air is 1. If the unit is used with Helium (K factor
1.454 relative to air) then the flow at 5VDC (i.e. the maximum flow) would
be (1.454/1)200 = 290.8 sccm
Example 2
For a 0-10.0 l/min unit calibrated for Argon the flow at 5.0VDC would be
10.0l/min. The K factor for Argon is 1.45. If the unit is used with Carbon
Dioxide (K factor 0.74) then the flow rate 5.0VDC would be
(0.74/1.45)10.0 = 5.10l/min
The accuracy of readings using K factors is not as good as that achieved
for the calibration gas. The accuracy obtained (typically ±3% for K factors
similar to the calibration gas) depends on the gas being used and the flow
rate.
For a list of common K Factors see Section J.
4. Changing The Flow Rate Set-Point (Using An External Voltage
Source)
The required flow rate is selected by adjusting the set-point voltage. The
normal control signal voltage is 0-5VDC with 0VDC corresponding to zero
flow and 5VDC being equivalent to the maximum rated flow of the unit.
This input is linear and scaleable allowing different flow rates within the
range of the unit to be selected. For example:
For a flow range of 0-500sccm:
/ K2)VDC for the full scale output.
1
A 5 VDC Input Signal would correspond to a flow rate of 500sccm
If a flow rate of 300sccm were required then the set-point would
be:
(300 ÷ 500) × 5 = 3.0VDC
M-4271/0707, pg. 15 of 26
If a gas other than the calibration gas is used then the adjusted maximum
(full scale) flow for the unit should be calculated using the K Factor for
that gas (see section C3 above).
A zero or negative set-point voltage will cause the solenoid valve to close
fully. Whilst closed, the valve is configured to withstand pressures up to 60
psig (higher pressures on request).
Caution: The flow controller valve will open if the pressure
exceeds 60psig. For safety it is recommended that a separate
positive shut-off valve is installed upstream of the controller.
5. Changing The Flow Rate Set-Point – FMA3400/3400ST Series
Only
On the FMA 3400/3400ST Series the set-point may be input from an
external source or be supplied internally.
For an external set-point, dip switch 1 should be OFF and dip switch 2
ON. See section C4 above for details of how to adjust the set-point using
an external voltage source.
For an internal set-point, dip switch 1 should be ON and dipswitch 2 OFF.
Adjustment of the internal set-point is made by turning the coarse and fine
set-point potentiometers on the front panel of the display, with the gas is
flowing, until the desired flow rate is achieved.
FMA 3400/3400ST Series Set-Point Potentiometers
6. Power Save Mode.
To improve valve performance and reliability over time, the FMA
3200/3400 Series features a Power Save Mode. This is activated after a
prolonged application of a zero or negative set-point. When a control
voltage greater than 0 VDC is applied after the Power Save Mode has been
initiated there may be a short delay (1-2 secs) before the valve actuates.
M-4271/0707, pg. 16 of 26
7. Zero Adjustments
The zero should be checked as detailed in section C part 2. If an
adjustment is needed the Zero Potentiometer should be carefully turned
until the output (VDC) becomes zero.
Caution: Do NOT adjust the Gain Potentiometer when adjusting
the zero or the unit will need to be recalibrated.
Making Zero Adjustments Using a Small Flathead Screwdriver
Care should be taken to only make small adjustments to the zero
potentiometer. If too much of an adjustment is made and difficulties are
being experienced in achieving a zero reading then turn the potentiometer
fully anti-clockwise and begin making small clockwise adjustments until a
zero reading is obtained.
8. Recalibration
If recalibration is required please contact the Omega Engineering
Customer Service Department.
9. Changing the Calibration Gas – FMA 3400/3400ST Series Only
The FMA 3400/3400ST Series may be calibrated for up to three gases.
These gases, their corresponding flow ranges and accuracy specifications
are detailed on the calibration certificate.
The calibration gas required is determined by selecting the corresponding
dip switch on the front panel of the display.
M-4271/0707, pg. 17 of 26
FMA 3400/3400ST Series Dip Switches
D.
Dip switch 4 is allocated to the primary calibration gas.
Dip switch 5 is allocated to the second calibration gas (if applicable).
Dip switch 6 is allocated to the third calibration gas (if applicable).
To select the gas, the dip switch should be turned ON. All other switches
allocated to gases (i.e. 4, 5 or 6 except the required switch/gas) should be
set to OFF.
Maintenance and Product Care
1. General
Inlet filters should be periodically checked and cleaned or replaced as
necessary.
Regularly check all electrical and process connections for damage or
deterioration.
If the sensor is to be stored, keep both the inlet and outlet ports sealed.
Do not allow any liquid or moisture to enter the sensor or damage will
occur.
2. Returning Units for Repair or Recalibration
To return a unit for repair or recalibration please contact the Omega
Engineering Customer Service Department. An Authorized Return (AR)
number will then be issued. The AR number should then be noted on the
outside of the package and on any correspondence. Further details may be
found on page 25 of this manual.
M-4271/0707, pg. 18 of 26
E.
Specifications
Series FMA 3200 FMA 3400 FMA 3200ST FMA 3400ST
Accuracy
(including linearity)
Repeatability ±0.25% Full Scale*
Pressure Rating 150 psig (10.3 bar) 500 psig (34.5 bar)
Pressure Sensitivity ±0.02% Full Scale* per psi (per 69 mbar)
Temperature Rating Operating Range: 5 to 55ºC
Temperature
Sensitivity
Valve Normally Closed
Body Leak Integrity 1x10-7 sccs of He
Wetted Materials Aluminum
O-Ring Material Viton®
Fitting Material Choose from acetal, brass, or stainless steel
±1.5% of
Full Scale*
Recommended Range (for best performance) : 10 to 40ºC
304 Stainless Steel
316 Stainless Steel
±1.5% of
Full Scale*
Second and
third gases
±3.0% F.S.*
Storage Range: 0 to 70ºC
±0.15% F.S.* or less per ºC
Positive Shut-off up to 60psig (4 bar)
±1.5% of
Full Scale*
303 Stainless Steel
304 Stainless Steel
316 Stainless Steel
±1.5% of
Full Scale*
Second and
third gases
±3.0% F.S.*
Epoxy
Recommended
Filtration
Compatible gases Clean, dry gases compatible with wetted materials
Output Signal 0-5VDC, Impedance greater than 2.5 KΩ
External Set-point
Signal
Internal Set-point
Signal
Warm-Up Time Less than 5 minutes
Integrated Display N/A 3½ digit N/A 3½ digit
Typical Power
Consumption
Peak Power
Consumption
Electrical
Connections
Certifications CE Approved
N/A Front Panel
Standard: 12 VDC @ 250 mA (12.5-15 VDC)
“E” Suffix: 24 VDC @ 130 mA (22-25 VDC)
Standard: 12 VDC @ 400 mA (12.5-15 VDC)
“E” Suffix: 24 VDC @ 260 mA (22-25 VDC)
Integrated 36” (92 mm) cable, terminated with:
Standard: 6-pin Mini-DIN male (PS/2 Style)
89/336/EEC (EN 55011 & EN 50082-1)
20 microns or less
Optional inline filters available
0-5VDC, Integrated 2MΩ load
N/A Front Panel
Adjustment
D1 Option: 9-pin D-Sub male
D2 Option: 15-pin D-Sub male
73/23/EEC Low Voltage Directive
Adjustment
*Specifications from 10-100% of rated flow. Linearity is best fit straight line. All calibrations
performed with air unless otherwise stated on calibration certificate.
M-4271/0707, pg. 19 of 26
F.
Dimensions
ALL DIMENSIONS IN INCHES (MILLIMETERS IN BRACKETS)
FMA 3200/3200ST Series - 1/4” Stainless Fittings Shown
M-4271/0707, pg. 20 of 26
FMA 3400/3400ST Series - 1/4” Stainless Fittings Shown
M-4271/0707, pg. 21 of 26
G.
Gas K Factors
Gas
Acetylene C2H2 0.589
Air - 1.000
Argon Ar 1.438
Butane C4H10 0.260
Carbon Dioxide CO2 0.739
Deuterium D2 1.000
Ethylene C2H4 0.598
Freon 11 CCL3F 0.330
Freon 12 CCL2F2 0.354
Freon 13 CCLF3 0.385
Freon 14 CF4 0.420
Freon 22 CHCLF2 0.460
Germane GeH4 0.570
Helium He 1.458
Chemical
Symbol
K Factor
Hydrogen H2 1.011
Krypton Kr 1.440
Methane CH4 0.721
Neon Ne 1.443
Nitric Oxide NO 0.990
Nitrogen N2 1.000
Nitrous Oxide N2O 0.710
Oxygen O2 0.991
Ozone O3 0.446
Propane C3H8 0.383
Sulfur Dioxide SO2 0.690
Xenon Xe 1.437
These K Factors are given for reference only and are not intended as a recommendation of
application suitability. Accuracy and response will be affected depending on the gas and
flow range. Check the compatibility of all wetted materials before using any gas other than
the calibration gas for the unit.
M-4271/0707, pg. 22 of 26
H.
Troubleshooting Guide
Symptom Possible Cause Method of Correction
Clicking noise from
controller
No response
Inaccurate control
Unit in error mode Check there is sufficient
pressure and that the flow
path is not restricted or
blocked
Unit wired incorrectly Check wiring is according to
Section B5
Loose connection Check all connectors and
wiring
Damaged connector pins Contact Omega Engineering
Blocked flow path Check flow path for
obstructions.
Piping leak before sensor Check all piping and
connections.
Insufficient power Check the power supply
output and increase if
necessary
Output load resistance too low Ensure the voltmeter or
data acquisition system or
display has an impedance of
greater than of 2.5kohm
Flow too low for the unit Ensure that the flow being
measured is within the
capabilities of the unit
Unit damaged or faulty Contact Omega Engineering
Particles in flow path Add filtration before the
sensor.
Flow path obscured Remove any debris or
blockage in the flow path
eg. PTFE tape.
Unit calibrated for a different
gas
Gas composition is variable Contact Omega Engineering
Fittings have been changed Replace the factory installed
Moisture in gas Ensure gas is clean and dry
Insufficient warm-up period Allow the unit to warm-up
Zero drift Verify the zero and adjust
The gain potentiometer has
been adjusted
Unit needs recalibration Contact Omega Engineering
Flow too high for the unit Ensure that the flow being
Check calibration certificate
and apply a “K” Factor to
readings if necessary.
fittings
for at least 5 minutes.
as necessary as explained in
Section C
Contact Omega Engineering
measured is within the
capabilities of the unit
M-4271/0707, pg. 23 of 26
Symptom Possible Cause Method of Correction
Inaccurate control
Problems with
rezeroing
Insufficient or varying power Check the power supply
output and increase if
necessary
Insufficient pressure Ensure the pressure (an
differential pressure) is high
enough o operate the unit.
Varying pressure Check the stability of the
pressure regulation and
improve if necessary.
Ambient temperature too high
or too low
Output load resistance too low Ensure the voltmeter or
Gas temperature too high or
too low
Unit damaged or faulty Contact Omega Engineering
Gas flow through unit not
completely stopped
Severe fluctuations in the
ambient temperature e.g. unit
in direct sunlight
Unstable power supply Check the stability and
Insufficient warm-up period Allow the unit to warm-up
Place the unit in a suitable
environment
data acquisition system or
display has an impedance of
greater than of 2.5kohm
Ensure the gas temperature
is within the recommended
operating range
Ensure there is no flow
through the unit. The
easiest way to do this is to
plug both the inlet and
outlet.
Carry out the rezero
procedure in a stable
environment
suitability of the power
source
for at least 5 minutes.
M-4271/0707, pg. 24 of 26
.
M-4271/0707, pg. 25 of 26
M-4271/0707, pg. 26 of 26
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