Kobold MAS Series, MAS-1000, MAS-2000, MAS-1100, MAS-2100 Instruction Manual

KOBOLD MAS Series

Thermal Mass

Flowmeters

March 1997

r2_12-13

Part Number:

IM-82

[phone] · [phone] · Fax [phone]

KOBOLD Instruments Inc

1801 Parkway View Drive · Pittsburgh, PA 15205

MAS Instruction Manual

The purpose of this instruction manual is to cover the following
Kobold Instruments Inc products:

Model MAS-1000 Flowmeter with Po

Model MAS-2000 Flowmeter with Polyamide body and no display.

Model MAS-3000 Flowmeter with stainless steel flow body and
display.

Model MAS-4000 Flowmeter with stainless steel flow body and no
display.

Model MAS-1100 Flowmeter with aluminum body and display.

Model MAS-2100 Flowmeter with aluminum body and no display.

Kobold Instruments’ MAS Series Flowmeters measure the mass
flow rate of gases in ranges from 0-10 standard cubic centimeters
per minute (SCCM) to 0-500 standard liters per minute (SLM). For
most models, accuracy is 1.5% of full scale over a wide temperature
and pressure range, and time response is 2 seconds to within 2%
of final flow. Certain models are rated at 1% or 5% of full scale.

lyamide body and display.

1

INTRODUCTION

1.1

Purpose

The MAS is ideal for a complete range of gas flow applications
including general process control, laboratories, instrument OEM’s,
gas panels, and flow calibration.

Figure 1-1

Tiltable Display is Viewed

from any Angle

Page 1

MAS Instruction Manual

CAUTION! Any application whatsoever related to humanCAUTION! Any application whatsoever related to human

CAUTION! Any application whatsoever related to human

CAUTION! Any application whatsoever related to humanCAUTION! Any application whatsoever related to human
respiration must have the written consent of Koboldrespiration must have the written consent of Kobold

respiration must have the written consent of Kobold

respiration must have the written consent of Koboldrespiration must have the written consent of Kobold
Instruments Inc.Instruments Inc.

Instruments Inc.

Instruments Inc.Instruments Inc.

The versatile MAS Flowmeter digitally displays the mass flow
rate directly in engineering units or percent of full scale. The

display is tiltable over 180° for easy viewing and can be removed

for remote mounting on a front panel.

The Kobold MAS directly monitors the mass flow rate of the gas.
This means it measures molecular flow – the measurement quality
of direct concern in most applications, such as human respiration,
chemical processes, combustion, and heating or cooling. No
temperature or pressure corrections are required, as in the case of
most other flow monitoring devices like rotameters, turbine meters,
and orifice plates.

Figure 1-2

MAS Operation
and Features

Direct Monitoring of
Mass Flow.

No temperature or
pressure corrections
required.

Unexcelled Performance.

● ±

1.5% accuracy.

●

0.5% repeatability.

●

2 second response time

Tiltable Display.

9 positions provide easy
viewing from any angle.

Connector.

9-Pin "D" Sub-type. Has
0-5 VDC or 4-20 mA
(optional) output signal
linearly proportional to
mass flow rate.

Input Power Jack.

Accepts 12 to15 VDC or
24 VDC input power from
Kobold power supply or
customer supplied power.

Inlet Screen.

Filters out particulates.
Easily removable.

Digital Display.

Gives mass flow
rate in engineering
units.

Zero and Span
Potentiometers.

Adjustable from
outside of enclosure.

Patented Sensor
Tube.

Straight, large-I.D.
sensor tube is easy
to clean.

Patented Laminar
Flow Bypass.

Provides a variety of
flow ranges. Unique
cutouts make range
changes easy.

Flow Body.

Corrosion resistant
plastic or stainless
steel.

FKM

rings standard.

"O"-

Inlet/Outlet Fittings.

Available with Female
NPT or Swagelok®
style compression
fittings.

Page 2

Mounting Holes.

The MAS mounts in any
position for convenience
of installation.

The MAS Flowmeter is a transducer requiring a 12-15 VDC (24
VDC optional) external power source. A 0-5 VDC or optional 4-20
mA output singal linearly proportional to gas mass flow rate is
provided for recording, data-logging, or control. A 9-Pin “D” sub­connector is provided for power input and signal output. The MAS
is available in several basic configurations with either
(female) or

1

/4 to 1/2 inch O.D. tube compression inlet/outlet fittings,

1

/4 inch NPT

with or without the digital display, or the optional power supply.

Gas enters the MAS flow body and divides into two flow paths.
Most of the flow goes through the laminar flow bypass. This creates
a pressure drop that forces a small fraction of the flow through the
sensor tube.

TWO COILS

MAS Instruction Manual

1.2

Principle of

Operation

SENSOR
TUBE

m

•

m

1

P

1

•

•

m

2

P

2

LAMINAR FLOW BYPASS

The patented* straight sensor tube is mounted parallel to the
bypass flow path. Since both paths are perfectly laminar, the ratio
of the total flow (

˙

m

) to the sensed flow (

˙

m

) is constant. Two

1

resistance temperature detector (RTD) coils around the sensor
tube direct a constant amount of heat into the gas stream.

RTD COILS

, T

R

1

1

·

m

1

R2, T

2

H

0

Figure 1-3

Two Flow Paths

CONSTANT HEAT, H

FIRST LAW OF THERMODYNAMICS

(HEAT IN = HEAT OUT)
H = m·

*U.S. Patent No. 4,487,062.

(T2 – T1) + H

1 Cp

H–H

m· =

Cp∆T

Figure 1-4

Measuring Sensor Flow

0

0

Page 3

MAS Instruction Manual

A

A

“GATES”

SECT. A-A

Figure 1-5

Changing Flow Ranges
is Easy with MAS’s
Patented Bypass

In actual operation, the gas mass flow carries heat from the
upstream coil to the downstream coil. The resulting temperature
difference T

is detected by the RTD coils and gives the output

2–T1

signal. Since the molecules of the gas carry away the heat, the
output signal is directly and linearly proportional to gas mass
flow.

MAS's patented laminar flow bypass makes changing of flow
ranges easy with the proper calibration facilities. Each of the two
bypasses in the optional Laminar Flow Bypass Set has a
combination of rectangular slots along its circumference as shown
in Figure 1-5 below.

1.3
Specifications

To change the flow range of your MAS, follow the instructions
provided with the Kobold Model EL Laminar Flow Bypass Set and
cut away the “gate(s)” leading to the right combination of laminar
flow paths in one of the two bypasses. This procedure requires
proper calibration facilities and minimal skill in electronics.

FLOW RANGES
_________________________________________________________________

_________________________________________________________________

_________________________________________________________________

Flow ranges specified are for an equivalent flow of nitrogen at 760 mm

Hg and 21°C (70°F). Other ranges are available.

GASES

Most gases; check compatibility with wetted materials; specify
when ordering.

Code SCCM Code S LM

01 0-10 07 0-1
02 0-20 08 0-2
03 0-50 09 0-5
04 0-100 10 0-10
05 0-200 11 0-20
06 0-500 12 0-30

13 0-40

DISPLAY

Page 4

31/2 digit LCD (0.5 inches tall); removable for remote mounting.

OUTPUT SIGNAL

Linear 0-5 VDC standard, 1000 ohms min. load impedance; 4-20
mA optional, 50 to 500 ohms loop resistance.

POWER REQUIREMENTS

12-15 VDC nominal; 100 mA max (24 VDC optional, specify when
ordering).

ACCURACY

±1.5% of full scale including linearity over 15 to 25 °C and 5 to 60

psia (0.35 to 4.2 kg/cm

2

); with special calibration ±1% of full scale

accuracy at a specific temperature and pressure is available.

REPEATABILITY

±0.5% of full scale.

TEMPERATURE COEFFICIENT

0.15% of full scale per °C, or better.

MAS Instruction Manual

PRESSURE COEFFICIENT

0.01% of full scale per psi (0.07 kg/cm2), or better.

RESPONSE TIME

800 ms time constant; 2 seconds (typical) to within ±2% of final

value over 25 to 100% of full scale.

PRESSURE DROP
____________________________________________________________

Typical Maximum Pressure Drop

_____________________________________________________________

Flow Rates (cm of Water)

100 SCCM .025

1 SLM .454
1 0 SL M 6.00
2 0 S L M 23.83
3 0 S L M 45.60

___________________________________________________________

4 0 S L M 83.36

GAS PRESSURE

150 psi (10 kg/cm2) gauge max; 20 psi (1.4 kg/cm2) gauge optimum.

LEAK INTEGRITY

–4

1×10

SCCS of helium max to outside environment.

GAS AND AMBIENT TEMPERATURE

0 to 50 °C.

Page 5

MAS Instruction Manual

1.15

(29.21)

3.05

(77.47)

4.16

(105.66)

(WITHOUT

DISPLAY)

5.38

(136.65)

3.50 (88.90)

1

/4" NPT

6.68 (169.67)

1

/4" SWAGELOCK

®

ALL DIMENSIONS IN INCHES

0.58

(14.73)

1.16

(29.46)

0.56

(14.22)

6-32 X 0.15 DP.

(SELF TAPPING)

0.75 (19.05)

0.38

(9.65)

0.13 (3.30)

2.75

(69.85)

3.00

(76.20)

0.125 DIA. THRU PANEL-2 PLACES;

FOR TWO 4-40 FLAT HEAD SCREWS

0.25 DIA. THRU; FOR 4 WIRES

0.88 (22.35)

1.00 (25.4)
PANEL MOUNTING HOLES

DIMENSIONS IN INCHES

(DIMENSIONS IN MILLIMETERS IN PARENTHESES)

SIDE VIEW

END VIEW

BOTTOM VIEW

Dimensions

WETTED MATERIALS

5% glass-filled Polyamide 6/6; 316 stainless steel; FKM “O”-

rings standard, FFKM and silicone O-rings optional.

WEIGHT

2 lb. (0.9 kg) net; 3 lb. (1.4 kg) shipping.

Page 6

MAS Instruction Manual

Many options are available for your Kobold MAS. Please consult
Kobold’s current Price List for the respective prices.

V4 (Optional) 4-20 mA output signal
C( ) Cable assembly, specify cable type (round or ribbon) and

length
T2 1-5 Channel Power Supply, in NEMA Box, 115 VAC
T4 1-5 Channel Power Supply, in NEMA Box, 230 VAC
T5 Power Supply, for one channel, 110 VAC
T6 Power Supply, for one channel, 230 VAC
UV Upstream valve
DV Downstream valve
M S Replacement mass flow sensor, includes “O”-rings and

mounting flanges
OV

Complete set of FKM “O”-rings
T P Tip plate for electrical enclosure
RD–( ) Remote display

1.4

Options

* U.S. and foreign patents pending.
® Registered trademarks:

Swagelok, VCO, VCR–Crawford Fitting Co.

Page 7

MAS Instruction Manual

2
INSTALLATION

2.1
Receipt of Your
MAS

2.2
Return Shipment

When
packing carton for damage incurred in shipment. If the packing
carton is damaged, the local carrier should be notified at once
regarding their liability. Kobold’s Customer Service Department
should also be notified immediately.

Customer Service Phone Number:

For our customers other than the USA, Canada and Mexico please
call the distributor from whom you purchased your MAS or call our
head office in Germany for the Kobold location nearest you:

Remove the packing slip from its envelope and verify that the
carton contains all parts listed. Inspect the carton and packing
material thoroughly to ensure that no spare parts or accessories
are mistakenly discarded. In case of shortages, please contact
Customer Service at the above phone number, or they may be
contacted in writing at the address listed in the next section.

Please do not return any equipment without a Return Material
Authorization, which is obtained from the Customer Service
Department. Information describing the problem, corrective action
or work to be performed at the factory, the purchase order number
that the equipment was purchased under, and the name of the
person to contact must be included with the returned equipment.
The use of a Return Material Authorization is for your benefit. It
makes the proper service and return of your equipment much
easier to accomplish.
Return shipping address:

the equipment is received, carefully check the outside

USA [phone], or Fax [phone]

Germany 49(0)61-92-29-90 or Fax [phone]

Non-North American customers may contact the KOBOLD
Messring GmbH Customer Service Department Technical
Assistance at:

NOTE: Equipment returned for repair that is found to be completely
operational will be subject to the current “no problem found”
billing rate.

Page 8

USA KOBOLD INSTRUMENTS INC.

1801 Parkway View Drive
Pittsburgh, PA 15205

Europe KOBOLD MESSRING GmbH

Nordring 22-24
65719 Hofheim/Ts.
Germany

CAUTION! The maximum pressure and temperature in theCAUTION! The maximum pressure and temperature in the

CAUTION! The maximum pressure and temperature in the

CAUTION! The maximum pressure and temperature in theCAUTION! The maximum pressure and temperature in the
flow line in which your MAS is to be installed must notflow line in which your MAS is to be installed must not

flow line in which your MAS is to be installed must not

flow line in which your MAS is to be installed must notflow line in which your MAS is to be installed must not
exceed 150 psig (10 kg/cmexceed 150 psig (10 kg/cm

exceed 150 psig (10 kg/cm

exceed 150 psig (10 kg/cmexceed 150 psig (10 kg/cm
respectively.respectively.

respectively.

respectively.respectively.

22

2

22

gauge) or 150 gauge) or 150

gauge) or 150°

gauge) or 150 gauge) or 150

F (65F (65

F (65°

F (65F (65

C),C),

C),

C),C),

MAS Instruction Manual

In order to ensure a successful installation, inlet and outlet tubing
or piping should be in a clean state prior to plumbing your MAS to
the system. MAS is applicable to

clean gas onlyclean gas only

clean gas only because

clean gas onlyclean gas only
particulates and other foreign matter may clog the sensor tube and
laminar flow element over a period of time. If the gas contains
particulate matter, install a high-efficiency, 50 to 100 micron, in­line filter upstream of the MAS.

Do not locate the MAS Flowmeter in areas subject to sudden
temperature changes, moisture, drafts, or near equipment radiating
significant amounts of heat. Allow adequate space for cable
connectors and wiring. If your MAS is to be mounted in other than
a horizontal position, the zero will need adjustment. See Section

5.2, R

CAUTION! Be sure the arrow on the side of the transducerCAUTION! Be sure the arrow on the side of the transducer

CAUTION! Be sure the arrow on the side of the transducer

CAUTION! Be sure the arrow on the side of the transducerCAUTION! Be sure the arrow on the side of the transducer
points in the direction of flow.points in the direction of flow.

points in the direction of flow.

points in the direction of flow.points in the direction of flow.

ECALIBRATION OVER THE SAME FLOW RANGE.

The MAS may be mounted to a chassis with two 6-32 self-tapping
screws. See Section 1.3, S

PECIFICATIONS, for hole dimensions.

2.3

Mechanical

Installation

Your MAS is supplied with either

1

/4 , 3/8 or 1/2 inch compression inlet and outlet fittings. These

or

1

/4 inch female NPT (standard)

fittings should not be removed unless your MAS is being cleaned

®

or calibrated for a new flow range. VCO

1

available on special order.

/4-inch pipe requires a good quality

or VCR® fittings are

paste pipe thread sealant and should be installed in the inlet and

1

outlet fittings 1

CAUTION! Over-tightening will crack the fittings andCAUTION! Over-tightening will crack the fittings and

CAUTION! Over-tightening will crack the fittings and

CAUTION! Over-tightening will crack the fittings andCAUTION! Over-tightening will crack the fittings and
shift calibration.shift calibration.

shift calibration.

shift calibration.shift calibration.

/2 turns beyond hand-tight.

For the first installation of compression fittings, simply insert the
tubing into the fitting. Make sure that the tubing rests firmly on
the shoulder of the fitting and that the nut is hand-tight. Scribe the
nut at the six o’clock position. While holding the fitting body steady

1

with a back-up wrench, tighten the nut 1

/4 turns, watching the
scribe mark make one complete revolution and continue to the nine
o’clock position. After this, the fitting can be reconnected by
snugging with a wrench. Do not fail to use a back-up wrench or the
inlet fitting may be damaged.

2.4

Plumbing

Connections

Page 9

MAS Instruction Manual

Figure 2-1

Plumbing Requirements
for Model’s 1100/2100

FLOW

➡

5.0"

(127 mm)

1

/2" NPT PIPE

(10 DIAMETERS)

EXAMPLE: Cross Section

CORRECT

1

/2" NPT pipe for

1

/2" NPT flow body

CAUTION! Do not mix or interchange parts of tube fittingsCAUTION! Do not mix or interchange parts of tube fittings

CAUTION! Do not mix or interchange parts of tube fittings

CAUTION! Do not mix or interchange parts of tube fittingsCAUTION! Do not mix or interchange parts of tube fittings
made by different manufacturers.made by different manufacturers.

made by different manufacturers.

made by different manufacturers.made by different manufacturers.

INCORRECT
Avoid use of compression
fitting on inlet of flow body. The
reduction of internal diameter of
the fitting results in a “jet”, creating
noise and affecting calibration.
DO NOT reduce down right at the
inlet with

1

/4" pipe.

2.50"

(63.5 mm)

1

/2" NPT PIPE

(5 DIAMETERS)

Finally, check the system’s entire flow path thoroughly for leaks
before proceeding to Section 3, O

CAUTION! All instruments are leak-tested prior to shipping.CAUTION! All instruments are leak-tested prior to shipping.

CAUTION! All instruments are leak-tested prior to shipping.

CAUTION! All instruments are leak-tested prior to shipping.CAUTION! All instruments are leak-tested prior to shipping.
To check your installation, test the fittings only. Do not useTo check your installation, test the fittings only. Do not use

To check your installation, test the fittings only. Do not use

To check your installation, test the fittings only. Do not useTo check your installation, test the fittings only. Do not use
liquid leak detectors such as Snoop® to search for leaksliquid leak detectors such as Snoop® to search for leaks

liquid leak detectors such as Snoop® to search for leaks

liquid leak detectors such as Snoop® to search for leaksliquid leak detectors such as Snoop® to search for leaks
inside or outside the MAS. Instead, monitor pressureinside or outside the MAS. Instead, monitor pressure

inside or outside the MAS. Instead, monitor pressure

inside or outside the MAS. Instead, monitor pressureinside or outside the MAS. Instead, monitor pressure
decay.decay.

decay.

decay.decay.

Page 10

PERATION.

MAS Instruction Manual

MAS flowmeters require a single +12 to +15 VDC power supply
capable of providing a minimum current of 100 mA. The MAS can
also be configured for +24 VDC power at 100 mA.

Operating power input is via either the DC power jack or the 9-pin
“D” connector on the side of the enclosure. Kobold offers the Model
MAS-5000 single channel power supplies for single transducer
applications and the Model MAS-5100 for powering up to eight
transducers through the "D" connector.

CAUTION! Do not supply + DC power at the “D” connectorCAUTION! Do not supply + DC power at the “D” connector

CAUTION! Do not supply + DC power at the “D” connector

CAUTION! Do not supply + DC power at the “D” connectorCAUTION! Do not supply + DC power at the “D” connector
while using an MAS-5000 power supply at the DC powerwhile using an MAS-5000 power supply at the DC power

while using an MAS-5000 power supply at the DC power

while using an MAS-5000 power supply at the DC powerwhile using an MAS-5000 power supply at the DC power
jack. Do not plug power connector into DB9 connector.jack. Do not plug power connector into DB9 connector.

jack. Do not plug power connector into DB9 connector.

jack. Do not plug power connector into DB9 connector.jack. Do not plug power connector into DB9 connector.
Damage to electronics will result.Damage to electronics will result.

Damage to electronics will result.

Damage to electronics will result.Damage to electronics will result.

The standard MAS is provided with a 9-pin “D” sub type connector
located on the side of the MAS enclosure as shown in Figure 2-2.
The pin numbers for this “D” connector are also shown in Figure 2­2, and the pin assignments are given in Table 2-1 on the next page.
The output signal is obtained from the 9-pin “D” connector. A 0 to
5 VDC output signal linearly proportional to gas mass flow rate is
standard. A 4-20 mA current loop signal is optionally available.
The mating connector is included.

2.5

Electrical

Connections

2.5.1

9-Pin “D”-Connector

Pin Assignments

When the MAS is configured for a remote display, connections are
made via the 9-pin “D” connector. Power connections for the
display and transducer are shared in this mode unless the accessory
MAS-5000 power supply is used.

“D” CONNECTOR

7
8
9

6

1
2
3
4
5

DC POWER JACK

Figure 2-2

“D” Connector and DC

Power Jack Location and

Number Assignments

Page 11

MAS Instruction Manual

Figure 2-3

Printed Circuit Board
Input/Output Solder Pad
Assignments (wires shown
are typical)

Table 2-1

The following connection points can be made through the “D”
connector or, in OEM applications, made through the circuit board
solder pad connections.

The display pad connections are shown for applications requiring
remote mounting of the digital display. The letters appear on the
display circuit board and are shown in Figure 2-3.
___________________________________________________________

____________________________________________________________

Pin No. Function Display Pad

1 No Connection N/A
2 Signal Common N/A
3 0 to +5 VDC Flow Signal N/A
4 + Power Supply (12 or 24 VDC)

*1, *2

(A)
5 Remote Display Flow Signal (D)
6 Remote Display Reference (C)
7 Power Common (B)
8 4 to 20 mA Return (Common) N/A

____________________________________________________________

9 4 to 20 mA Output N/A

NOTE: the numbers on the connector plug may not agree with the
numbering system as it appears on our Figure 2-2 (on previous
page). It is important to make sure that the proper wires are in the
proper location rather than the proper number. Most connectors
utilize a standard numbering scheme but there are a few that do
not.

The remote display connects through the 9-pin “D” connector only.
The pads A-D in the top right of the main circuit board are for
integral display mounting only.

*1 Power supply voltage must be specified at time of order. Operating a 12 VDC meter at

*2 Do not supply + DC power at the “D” connector while using a power supply at the DC

Page 12

24 VDC will cause damage. Running a 24 VDC meter at 12 VDC will result in faulty
operation.

power jack. Both supplies may be damaged.

MAS Instruction Manual

As shown in Figure 2-4, the digital display on your MAS may be
removed and mounted remotely on a front panel. The MAS
transducer is mounted at any convenient location in your system.

Remote installation is not recommended unless you possess the
proper soldering tools and skills to accomplish the job. Remote
installation of the digital display is accomplished by following
these steps:

1. Remove the digital display from your MAS by following the
procedure described in Section 2.5.3, OEM E

TIONS.

LECTRICAL C ONNEC-

2. Gain access to the printed circuit board (PCB) also by following
the procedure in Section 2.5.3, OEM E

LECTRICAL C ONNECTIONS.

3. Very carefully unsolder the four short leads from the PCB to the
display.

4. Gain access to the display circuit board by removing the two
snap rings (No. 36) and opening the “clam shell” display enclo­sure. Remove the four short wires by carefully unsoldering.
Solder the longer four wires (26AWG, 100 ft. max shielded cable
recommended) to the digital display and solder the other ends
to the appropriate pin numbers of the 9-pin “D” connector as
shown in Figure 2-3 and Table 2-1 (on previous page).

2.5.2

Remote Installation of

Digital Display

5. Reassemble the MAS, replacing the display base (No. 35) with
the Model TP Plain Top Cover (No. 28).

6. Make the necessary plumbing connections to the unit.

7. Mount the digital display as shown in Figure 2-4 referring to the
panel mounting hole dimensions in Section 1.3, S

PECIFICATIONS.

Figure 2-4

Remote Installation of

Digital Display

Page 13

MAS Instruction Manual

2.5.3
OEM Electrical
Connections

The OEM version MAS flowmeter has an electrical port (hole) on
its side for electrical input/outputs. This port is just above the
input power jack (see Figure 2-2). Wires entering the MAS via this
port are soldered to the printed circuit board as shown in Figure 2-

3. The solder pad assignments are given in Table 2-1.

How to Gain Access to the MAS’s Printed Circuit Board (PCB):
To gain access to the PCB to make the solder connections, please
refer to the exploded view in Appendix A and follow these simple
steps.

1. If your MAS has the digital display:

(a) First, remove the display by carefully rotating the display
until it hits the top plate. Slowly continue to rotate until this
lever arm action snaps out the two yokes holding the display
(Nos. 30). Use extra caution during this operation as excessive
force will break the delicate wire connections. Carefully move
the display assembly to expose the two screws securing the
display base (No. 35). Do not exert excessive force on the display
while rotating as doing so could crack the LCD display.

(b) Next, remove the two screws (Nos. 21) in the display base
(No. 35) and the two screws (also Nos. 21) in the back of the
enclosure (No. 10).

2.5.4
Using Kobold’s Single,
Dual, and Flo-Box™
Electronics

(c) The top, front, and back sides of the enclosure can now be
removed, (the front slides out towards you and perpendicular to
the flow path) exposing the PCB.

2. If your MAS does not have the digital display:

(a) Remove the label (No. 29) from the plain top cover (No. 28)
to expose the two screws (Nos. 21).

(b) Then follow steps 1(b) and 1(c) above.

To reassemble, just reverse the process.

For applications requiring flow totalization or alarms simply
order the optional Model EC-( ) cable to connect to the rear panel
of Kobold Instruments’ Single-Channel, Dual-Channel, or Flo­Box (1-5 Channels) Electronics. The Kobold electronics will provide
you with a selectable digital readout for each channel, input power,
high, low, or window alarms, and optional flow totalization.

Page 14

MAS Instruction Manual

Quick operating instructions are given on the first page of this
manual.

Following are important notes and comments regarding the Quick
Operating Instructions.

NOTE 1 R

EFERENCING THE FLOW RATE TO OTHER TEMPERATURE AND

PRESSURE CONDITIONS:
The gas flow rate output of your MAS is referenced to “standard”

conditions of 21°C (70°F) and 760 mm of mercury (1 atmosphere),

unless you have specified otherwise. Be sure you know the reference
conditions of your MAS, because it may make a difference if you are
comparing the output of the MAS with another type of flow meter.
For example, the output reading of the MAS will be approximately

7% lower if it is referenced to 0°C rather than 21°C. Appendix B

shows how to convert the flow rate output of your MAS to other
standard conditions and how to find the flow rate referenced to the
actual temperature and pressure conditions in the pipe where your
MAS is located.

NOTE 2 A

CCURACY:

The standard accuracy of the MAS is ±1.5% of full scale. The ±1.5%

of full scale accuracy means the 0-5 VDC output signal is accurate

to within ±0.1 VDC, and the 4-20 mA output is accurate to within
±0.4 mA. This means, for example, that the output signal for zero
flow can be as much as ± 0.1 VDC or ±0.4 mA. Please note if you get

an output signal at zero flow (as long as it is within either of these
two ranges) it does not mean your MAS is malfunctioning. For
MAS’s with the digital readout, the accuracy is simply 1.5% times
the full scale flow rate listed on your MAS’s front label. For
example, if your full scale is 10 SLM, the digital readout will be

accurate to ±0.2 SLM, and the reading at zero flow may be as much
as ±0.2 SLM and still be within the stated accuracy specification.

3

OPERATION

3.1

Quick Operating

Instructions

3.2

Notes to Operating

Instructions

NOTE 3 O

VERRANGING:

If the flow rate exceeds the full scale range listed on your MAS’s
front label, the output signal and digital display (if you have it) will
read a higher value.

The MAS has not been calibrated for overranged flows and probably
will be both non-linear and inaccurate. If the supply voltage is only
12 VDC, the overranged reading may only exceed the full scale
reading by 10% maximum. If the supply voltage is higher, such as
with the 24 VDC option, then the output can exceed full scale by as
much as 50%, or more. If you have the digital display, the display
can not exceed the four digits 1999. If the flow rate exceeds 1999 the

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MAS Instruction Manual

right most digits will blank and only the left-hand “1” will appear
on the display.

Overrange conditions are indicated by the display and/or output
going to a high level, above the full scale range. After the overrange
condition has been removed, it may take several seconds for the
MAS to recover and resume normal operation. This will not harm
the instrument.

NOTE 4 O

PTIONAL 4-20 mA OUTPUT S IGNAL:

The 4-20 mA output signal current flows from the 4-20 mA output
pin on the “D” connector through the load (50 to 500 ohms) to
ground (see Section 2.5.1, 9-P

IN “D” CONNECTOR P IN A SSIGNMENTS).

Figures 3-1 and 3-2 illustrate single and multiple installations
with current loop outputs.

NOTE 5 Z

ERO AND SPAN ADJUSTMENTS:

The zero and span potentiometers are accessed through marked
ports on the right side of your MAS. If your zero output is more than

±1.5% of full scale, you may adjust the zero potentiometer when

you are absolutely certain that you have zero flow.

Since the output does not indicate negative numbers, it is necessary
to adjust down from a slightly positive reading. Slowly rotate the
zero pot clockwise until a positive reading is indicated. To complete
the zero adjustment, slowly turn the pot counterclockwise until
zero is reached.

Normally, span adjustments are not made unless you areNormally, span adjustments are not made unless you are

Normally, span adjustments are not made unless you are

Normally, span adjustments are not made unless you areNormally, span adjustments are not made unless you are
calibrating your MAS, as described in Section 5. calibrating your MAS, as described in Section 5.

calibrating your MAS, as described in Section 5. The span

calibrating your MAS, as described in Section 5. calibrating your MAS, as described in Section 5.
adjustment should not be used unless you have a known precise
non-zero flow rate that you wish to match.

NOTE 6 A
Unless specified otherwise, your MAS has been calibrated for

installation with the flow direction in the horizontal plane (±15°)

with the enclosure facing upward. If your actual installation
orientation is different, you will have to make a small zero
adjustment.

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