Martek Mark 25 User manual

Martek Instruments, Inc.
Mark 25
Dissolved Oxygen
Analyzer
Instruction Manual

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WARRANTY POLICY
Unless otherwise stated, MARTEK INSTRUMENTS, INC. warrants this equipment
to be free from defects in material and workmanship and to perform in
accordance with applicable specifications for five years (one year for portable
equipment) from date of shipment. All conductivity sensors are guaranteed for
life.
MARTEK will provide free service at the factory, including parts, labor and
transportation back to the customer, for any malfunction of its products which
are returned transportation charges prepaid.
Customers desiring to return a product to MARTEK for repair should contact the
Service Department by telephone at [phone] or fax [phone] or via
our website at www.martekinstruments.com to obtain return authorization. The
information required at this time will be the complete model number and serial
number of the product and a brief description of the problem.
All shipments to MARTEK must be freight prepaid and addressed as follows:
MARTEK INSTRUMENTS, INC.
2609 Discovery Drive
Raleigh, NC 27616
Attn: Repair Department
A complete and detailed statement of the reason for return must accompany the
unit. If possible, include a copy of sample reading or a printout.
Returned units must be packed as well as they were when first shipped. If
possible, use the original packing. Do not return detachable cords or manuals
with the unit.
MARTEK reserves the right to void this warranty if the product has been
subjected to misuse, neglect, accident, improper installation or application, and
for consumable items such as batteries, membranes, or solutions.
This warranty is expressly in lieu of all other obligations or liabilities on the part
of MARTEK. MARTEK neither assumes nor authorizes any other person or
organization to assume on behalf of Martek any other liability in connection with
the sales or use of MARTEK instrumentation.

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MARK 25 TABLE OF CONTENTS
1. IntroductionPage
1.1 Description ……………………………………………………………………………….3
1.2 Specifications ……………………………………………………………………………4
2. Installation
2.1 Panel Cutout for Monitor ..………………………………………………………………5
2.2 Sensor & FlowChamber Dimensions ..………………………………………………. 5
2.3 Electrical connections to the monitor ……………………………………………….…6
3. Operation
3.1 Keyboard & display……………………………………………………………………….7
3.2 The CALIB Key...…….….…………………………………………………………………8
3.3 Calibrating Temperature.…………………………………………………………………8
3.4 Calibrating Dissolved Oxygen ..………………………………………………………….9
3.5 Setting Alarms…………….. …….………………………………………………………..9
3.6 Setting Recorder Outputs….……………………………………………………………10
3.7 Setting the Password..…….…………………………………………………….……….11
3.8 Setting the ID Number…………………….……………………………………………..11
3.9 Changing the Serial Output……………………………………………………….……..11
3.10 Setting the Auto-Ranging Function….…………………………………………….….12
3.11 Troubleshooting……………………….…………………………….…………………..13

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1. Introduction
1.1 Description
The Mark 25 Dissolved Oxygen Analyzer is a simple, lowcost, 4 channel,
microprocessor-based monitoring system designed for ultrapure water applications. The
system consists ofa readout module that can be used with up to four galvanic-style
dissolved oxygen sensors; each sensor being placed into a separate flowchamber.
A large 4 digit LED displayindicates either temperature,parts-per-million (ppm) or
parts-per-billion (ppb) dissolved oxygen. An 8-keymembrane keypad allows the
operator to quicklysetup and calibrate the analyzer.
The Mark 25 measures dissolved oxygen in four ranges; 0-20 ppb, 0-200 ppb, 0-2
ppm, and 0-20 ppm. Automatic calibration within the Mark 25 provides a fairlyreliable
measurement. However, comparison to a referee system remains the most accurate
method ofcalibration available. (Please refer to Martek’s Mark 21 Portable Dissolved
Oxygen Analyzer for further information).
Four alarm set points with relaycontacts are standard in addition to four analog
recorder outputs (0-20 mA) and a serial RS232 digital output for hookup to external
recording equipment. For maximum flexibility, alarm set points and analog outputs
can be assigned to anyrange on anyparameter on anychannel.
Housed in a ¼ DIN corrosion-resistant plastic case, the readout module can be panel
mounted with a minimum oftools. The analyzer accepts power inputs from 97 to 240
VAC 50/60 Hzor 24 Vdc and comes with an ON/OFF switch located on the rear panel.
Alarm and recorder wires are easilyinstalled in removable terminal strips.
Sensors connect via a DB-9 connector located on the rear panel ofthe Mark 25 and the
sensors mount easilyto anyflat surface. In addition, Martek offers adapter plates
specificallydesigned to cover the space occupied byother brands ofconductivity
analyzers.
Sensors come standard with 6 feet (2 meters) ofcable.

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1.2 Specifications
ParameterRangeAccuracyResolution
Dissolved Oxygen0-20.00 ppb+0.1 ppb 0.01 ppb
0-200.0 ppb+1.0 ppb 0.1 ppb
0-2.000 ppm+0.01 ppm 0.001 ppm
0-20.00 ppm+0.1 ppm 0.01 ppm
Temperature0-50.0o C+0.1o C 0.01o C
Power: 97-240 VAC, 50/60 Hz, 24Vdc, fuse protected
Recorder Output: Four, scaleable 0-20 mA DC analog & RS232C serial ASCII digital output
Alarm Output: Four solid-state relays, 5 amp, 250 V
Weight: 2 lbs (0.9 kg) including one sensor with 6 feet (2 meters)
Construction: Readout Module Case: ABS plastic, NEMA 12 (IP65)
Sensor: Type 316 Stainless Steel, Delrin, CPVC, Platinum& lead, Teflon
Cabling: 8-conductor, 24 gauge, PVC jacket, shielded, 0.25 inch (0.63 cm)
Dimensions: ¼ DIN case, 6.51 x 3.78 x 3.78 (165.5 x 96 x 96 mm) LWH
Installation: Panel mount (mounting hardware included). Recommend mounting flowchamber
and sensor vertically.
Flowrate: 50-250 ml/min

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2. Installation
2.1 Panel Cutout for Monitor2.2 FlowChamber Mounting
Bracket
3.60”2.20”
.266” dia.
3.60”2.00”
1.25”
Panel Cut-out
2.3 Sensor & FlowChamber Dimensions
2.25”
4.25”3.50”

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2.4 Electrical connections to the monitor
Alarm OutputsRecorder Outputs
ON/OFF
Switch
AC Cord
RS232
Digital Output RS2321234
Sensors
To set up the Mark 25 for operation, simplyplug the sensor connector in, then plug the
AC power cord into a properlygrounded outlet. Ifrecorder, digital or alarm outputs are
to be used, make certain the Mark 25 is unplugged before connecting the cable to the
appropriate recorder or computer. Followthe wiring diagram belowfor hooking up the
Mark 25 alarm and analog recorder outputs:
ALARMRECORDER
Channel 1 NO/NCChannel 1 4-20 mA
COMMON
Channel 2 NO/NCChannel 2 4-20 mA
COMMON
Channel 3 NO/NCChannel 3 4-20 mA
COMMON
Channel 4 NO/NCChannel 4 4-20 mA
COMMON

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3. Operation
3.1 Keyboard and display
The Mark 25 front panel consists ofa
4 digit red LED display, 3 parameter and
channel LED’s, an alarm LED, and an 8-
keykeypad. The displayis used to
present all parameter measurements,
operator prompts and system errors.
The keys are arranged in two rows, four
keys in each row.
The top row of keys consist ofthree
color-outlined function keys and are
used to perform instrument operations
such as selecting which parameter to
view, what range the parameter is to be
viewed in, parameter calibration and
system set up.
The bottom rowof keys are multi-
colored, multi-legend keys and are used
in conjunction with the function keys.
The same colored legends correspond
to the same colored function key.
The arrowkeys are used to view
channels, select functions during setup
and calibration, and increment or
decrement a displayed value.
READ key - When the <READ> keyis
pressed, the Mark 25 will display rd. If
one ofthe bottom keys is selected, the
parameter high-lighted in red will be
displayed and its corresponding LED lit.
RANGE key - Range changes can be
made manuallyfor dissolved oxygen. To
displayand/or change the range, press
the <RANGE> key, then select one of
the following keys:
LOW= rG 1: 0-20 ppb
MED = rG 2: 0-200 ppb
HIGH = rG 3: 0-2 ppm
DOWN ARROW= rG 4: 0-20 ppm
UP ARROW= rG A: Auto-ranging
NOTE: Manually changing the range for
dissolved oxygen changes the analog
recorder output scaling. See Section 3.6
for details.
Viewing a different channel is easily
done bypressing the <UP> or <DOWN>
arrowkey. The parameter LED’s to the
left ofthe Mark 25 displayalso indicate
which channel is being viewed. Channel
ID’s are as follows:
Red LED - Channel 1
Green LED - Channel 2
Red/Green LED - Channel 3
Flashing Red LED - Channel 4
READ Range CALIB
o
C
LOW
ZERO
PPM
MED
SPAN
PPB
HIGH
RUN
oC
PPMALARM
PPB
DISSOLVED OXYGEN ANALYZER
www.martekinstruments.com

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3.2 The CALIB key
All setup and calibration functions are
conducted via the <CALIB> key. The
<CALIB> allows you to set the following:
• Calibrate temperature and
dissolved oxygen
• Assign and set alarm points
• Assign and set recorder outputs
• Set a password
• Set up an analyzer ID and serial
output
Once the sensors have been connected
to the Mark 25, the power cord can be
plugged into anyoutlet supplying 97-240
V AC 50/60 Hzpower. When the Mark
25 is switched on, it will immediately
start monitoring temperature.
Pressing the <CALIB> keywill cause
the Mark 25 to displaya flashing oC.
Ifyou continue pressing the <DOWN
ARROW> keythe displaywill flash the
following prompts: dO, ALA, rEC, PAS,
uSr. After uSr, the Mark 25 returns to
monitoring temperature.
Here are two basic rules to remember
when using the <CALIB> key:
1. Pressing the <UP ARROW> keywill
select anyflashing prompt.
2. Pressing the <RUN> keywill return
the Mark 25 to the monitoring mode.
3.3 Calibrating Temperature
The Mark 25 can be calibrated
automaticallyor manuallyfor
temperature.
NOTE: Automatic, electronic calibration
is a less accurate method of calibration.
For best results, the Mark 25 should be
calibrated to ASTM or NIST- traceable
standards.
To calibrate temperature, press the
<CALIB> key. The displaywill flash oC.
To select temperature, press the <UP
ARROW> key. The flashing will stop.
Next, press the <ZERO> key. The Mark
25 will displaythree calibration bars and
automaticallyzero the temperature
before returning to the monitoring mode.
To span temperature, press the
<CALIB> key, then the <UP ARROW>
keywhen the temperature prompt is
displayed. Next, select the <SPAN> key.
The Mark 25 will display Aut which is
short for Automatic.
To automaticallycalibrate temperature,
press the <UP ARROW> key. After the
calibration bars appear, the Mark 25 will
brieflydisplaya span temperature of
50.0 before returning to monitor mode.
The Mark 25 has nowbeen calibrated
for temperature.
To manuallycalibrate temperature,
simplypress the <DOWN ARROW> key
when Aut is displayed. The Mark 25 will
momentarilydisplaythree lines, then a
number indicating the input voltage will
appear in the display. Once this number
has stabilized, press the <CALIB> key
and select the appropriate span value
using the up or down arrowkeys (the
displaydefaults to 25 deg. C). When
complete, press the <CALIB> keyto

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enter the data into the Mark 25’s
memory.
3.4 Calibrating Dissolved Oxygen
Calibrating dissolved oxygen follows the
same procedure as the temperature
calibration. However, there are several
differences.
Press the <CALIB> key, then the
<DOWN ARROW> keyuntil dO is
flashing. Followthe same procedure for
zero calibration for dissolved oxygen
that was used for temperature.
To span dissolved oxygen, press the
<CALIB> keyand select the D.O.
prompt. Next, press the <UP ARROW>
keywhen the Aut prompt is displayed.
The Mark 25 will displaythe calibration
bars then brieflydisplay 20.00 ppm
before returning to the monitor mode.
NOTE: If the auto-ranging function is
OFF while the Mark 25 is monitoring
dissolved oxygen and the measurement
exceeds the current selected range, the
Mark 25 will display Err. If an error
message occurs, you must select a
higher range.
3.5 Setting Alarms
The Mark 25 has four alarm set points
that can be assigned to anyparameter
on anychannel.
Press the <CALIB> until the display
indicates the alarm prompt, ALA. Next,
press the <UP ARROW> key. The
displaywill prompt with AL 1 and all
parameter LED’s will be lit. The <UP
ARROW> keycan be used to change
the alarm set point to 2, 3, or 4.
To assign a particular alarm set point,
press the <CALIB> key. The Mark 25
will displaythree bars. The bars indicate
no alarm set point. Use the <UP> or
<DOWN ARROW> keys to select
temperature (t), or dissolved oxygen
(do). Press the <CALIB> keyto select
the desired parameter.
The Mark 25 will then display Lo. To
select a lowset point, press the
<CALIB> key. Ifa high alarm set point is
desired, use the <UP> or <DOWN
ARROW> keyto change the displayto
hi then press the <CALIB> keyto
select.
The Mark 25 will display .000 (dissolved
oxygen is selected) though the decimal
point mayvarydepending on the range
previouslyselected.
Use the <UP> or <DOWN ARROW>
keyto change the value to the desired
alarm set point. When the desired set
point is reached, press the <CALIB> key
to set and activate alarm.
NOTE: For convenience, pressing the
<RANGE> key will advance the digit left
of the decimal point.
To disable alarm, return the set point
value to .000.
Once an alarm set point has been
assigned to a particular parameter on a
channel, it cannot be assigned to
another parameter or channel until it
has been disabled.
When the Mark 25 reaches an alarm
state, the Alarm LED will light and the
alarm relayactivate. The factory-set
position for the alarm relays is
NORMALLY OPEN. To change to a
NORMALLY CLOSED position, contact
Martek Instruments.
NOTE: The AlarmLED will blink if there
are active alarms that are not being

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viewed and will remain steady if the
channel viewed is in an alarmstate.
3.6 Setting Recorder Outputs
The Mark 25 comes standard with four
4-20 mA analog recorder outputs and
one RS232 digital output. Like the alarm
set points, the four analog recorder
outputs can be assigned to anyrange of
anyparameter on anychannel.
Press the <CALIB> until the display
indicates the recorder prompt, rEC.
Next, press the <UP ARROW> key. The
displaywill prompt with ou 1 and all
parameter LED’s will be lit. The <UP
ARROW> keycan be used to change
the recorder output to 2, 3, or 4.
To assign a particular analog output,
press the <CALIB> key. The Mark 25
will displaythree bars. The bars indicate
no analog output assigned. Use the
<UP> or <DOWN ARROW> keys to
select temperature (t) or dissolved
oxygen (do).
NOTE: A decimal point will be present
for do which indicates which one of the
four ranges the channel is currently
using. The range can be changed by
pressing the <RANGE> key.
When the desired parameter is
displayed, the standard 4-20 mA output
range can be changed to anyvalue
desired. In addition, a “balance” is
provided to “fine-tune” each end ofthe
recorder range.
To change the lower end ofthe recorder
range, press the <ZERO> key. The
Mark 25 will display 4.00. Use the <UP>
or <DOWN ARROW> keyto change the
number to the desired value. When the
desired value is reached, press the
<CALIB> keyto set the value in
memory.
At this point, the Mark 25 will display
000. This is the “balance”. Use the
<UP> or <DOWN ARROW> keyto
change the value in order to make the
lower end ofthe recorder range agree
with the external recorder. When the
desired balance is reached, press the
<CALIB> keyto set the value in
memory.
The same procedure is used to change
and “balance” the upper range ofthe
recorder output. To exit the menu,
simplypress the <RUN> key.
To disable anyassigned analog
recorder output, select the particular
output and press the <CALIB> key.
Once the parameter is displayed, use
the <UP> or <DOWN ARROW> keys
until three bars are displayed. Press the
<CALIB> keyto disable the output.
Once a recorder output has been
assigned to a particular parameter on a
channel, it cannot be assigned to
another parameter or channel until it
has been disabled.
NOTE: When the auto-ranging function
is OFF, changing a dissolved oxygen
range with an assigned analog output
automatically changes the scaling of the
recorder output to the new range.
When the auto-ranging function is ON,
the assigned analog output will remain
in the range it was assigned to.
When the RS232 digital output is used,
calibration is not necessary. However,
the receiving computer must be set up
to accommodate the Mark 25’s digital
output configuration:
Baud Rate - 9600
Parity- Even
Word length - 7
Stop Bit - 1

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A communication program such as
PROCOMM or Microsoft HYPERLINK
can be used to write data from the Mark
25 to a computer file which can then be
imported into a spreadsheet program
such as EXCEL or LOTUS NOTES.
The data will be displayed in the
following format:
ID, Chan, Temp, Dissolved Oxygen.
3.7 Setting the Password
The Mark 25 can be assigned a numeric
password to prevent unauthorized
personnel from changing anyofthe
settings.
Press the <CALIB> until the display
indicates the password prompt, PAS.
Next, press the <UP ARROW> key. The
displaywill prompt with 1999 and all
parameter LED’s will be lit and flashing.
Use the <UP> or <DOWN ARROW>
keys to change the displayed value to
anynumber other than 0. When the
desired value has been reached, press
the <CALIB> keyto set and activate the
password.
Once the password is enabled, the
displaywill default to 1999 whenever the
password prompt is selected. To gain
access to anyother function, you must
use the arrowkeys to scroll to the
correct value password then press the
<CALIB> key.
To disable the password, use the <UP
ARROW> keyto move the value to 000
then press the <CALIB> key. The
password function will then be disabled.
3.8 Setting the ID Number
The Mark 25 can be assigned a three
digit numeric ID number that will be
displayed on the digital output.
Press the <CALIB> until the display
indicates the user prompt, uSr. Next,
press the <UP ARROW> key. The
displaywill prompt with id and all
parameter LED’s will be lit and flashing.
When the <CALIB> is pressed, the Mark
25 will display 000. To assign an ID
number, use the <UP> or <DOWN
ARROW> keys to change the displayed
value to anynumber other than 000.
When the desired value has been
reached, press the <CALIB> keyto set
the ID number.
To disable the ID number, use the <UP
ARROW> keyto move the value to 000
then press the <CALIB> key. The ID
function will then be disabled.
3.9 Changing the Serial Output
The Mark 25 provides a standard
RS232 digital output. This output can be
configured in one oftwo ways:
1. Polling - The Mark 25 will provide the
digital output onlywhen polled bythe
host computer.
2. Periodic - The Mark 25 will
automaticallyprovide a digital output
at a 30 second interval.
Press the <CALIB> until the display
indicates the user prompt, uSr. Next,
press the <UP ARROW> key. The
displaywill prompt with id and all
parameter LED’s will be lit and flashing.
Use the <UP> or <DOWN ARROW>
keyto advance to the serial prompt,
SEr. When the <CALIB> is pressed, the
Mark 25 will display PoL. To change the
output to periodic interval, press either

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the <UP> or <DOWN ARROW> key
until the Mark 25 displays PEr.
To return to the monitor mode, press the
<RUN> key.
3.10 Sensor Design & Maintenance
The dissolved oxygen sensor is a
galvanic-style sensor using a platinum
cathode, lead anode, potassium iodide
electrolyte and a gas-permeable Teflon
membrane.
The dissolved oxygen sensor consists of
five principle parts:
• Spindle
• Outer body
• Filler Valve
• Membrane Ring
• Teflon Membrane
Refer to the photos at the back ofthis
manual for additional information.
The sensor is normallyshipped dryfrom
the factorywithout electrolyte or a
Teflon membrane installed. The
following procedure should be used
when changing the membrane or
replacing the electrolyte.
1. Turn the Filler Valve clockwise until it
stops.
2. Unscrewthe black Outer Body
counter-clockwise and remove it
from the graySpindle. Emptyout
anyelectrolyte still in the Outer
Body.
3. Unscrewthe stainless steel
Membrane ring from the Outer Body
and remove the old membrane.
4. Place a newmembrane in the
bottom ofthe Membrane Ring and
place several drops ofelectrolyte
onto the Membrane.
5. Screwthe Membrane Ring onto the
Outer Bodyand gentlytighten.
6. Using the dropper from the
electrolyte bottle, carefullyfill the
four small flow-through holes located
around the platinum tip ofthe
Spindle.
7. Fill the Outer Bodywith electrolyte
just above the interior ledge ofthe
Outer Body.
8. With the Filler Valve facing up at a
45oangle, screwthe Outer Body
back onto the Spindle and gently
tighten (some electrolyte should flow
out ofthe Filler Valve).
9. Gently screwout the Filler Valve
until it stops (two or three threads
should be visible).
10. Followthe normal calibration
procedure.
Ifthe dissolved oxygen sensor is not
going to be immediatelyused, fill the red
vinyl wetting cap with water and place
over the Membrane Ring squeezing as
much air from the cap as possible.
Ifthe sensor is not to be used within two
weeks, emptythe electrolyte out ofthe
sensor, dryall ofthe parts and store the
probe in a cool place.
Normally, verylittle maintenance is
required for the dissolved oxygen
sensor and it can operate for weeks,
even months, without the need to
change the electrolyte or membrane,
especiallyifthe sample stream has little
or no dissolved oxygen present.
However, over time or in a sample
stream with a high dissolved oxygen
content, lead oxide will form on the lead

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anode portion ofthe Spindle. A possible
indication oflead oxide build-up is lower
than normal readings due to less
surface area on the lead anode. The
lead strip will appear dull and possibly
have yellowdeposits near the edges.
To clean the lead anode, simplytake a
toothbrush or plastic scouring pad (i.e.
Scotch-Brite) and gentlyscrub the lead
anode with distilled water until it shines.
You should also check the platinum
cathode tip and the four flow-through
holes for dirt or debris. Ifanyexists, use
a fine wire to clean the holes.
NOTE: Do NOT scrub the platinum
cathode. However, you can polish the
platinum tip using a polishing cloth.
Lastly, make sure the o-rings used in
the Outer Body, Filler Valve, and Flow
Chamber are intact and in good
condition.
When placing the dissolved oxygen
sensor into the stainless steel Flow
Chamber, followthe steps outlined
below:
1. Gentlyremove the red vinyl wetting
cap from the end ofthe dissolved
oxygen sensor.
2. Carefullyinsert the dissolved oxygen
sensor into the flowchamber until it
rests flush with the top ofthe
chamber. Anytwisting of the probe
should always be clockwise. Place
the locking nut over the dissolved
oxygen sensor cable and secure it
firmlyonto the flowchamber.
3. To hook up sample flowto the Flow
Chamber, place the inlet flowon the
left fitting (with the mounting bracket
facing awayfrom you) and the outlet
flowon the right fitting. Ifthe Flow
Chamber is to be permanently
mounted on-line, stainless steel
fittings with ¼ inch stainless steel
tubing is recommended. Ifthe
installation is a portable application,
nylon or heavy-wall Tygon tubing
maybe used.
3.11 Troubleshooting
The Martek Mark 25 represents over
thirtyyears ofexperience in water
qualitymeasurements and, as such, has
been designed to provide simple,
reliable operation for manyyears.
To obtain optimum performance from
the Mark 25, care should be taken to
ensure the sensor has adequate flow
and is free ofobstructions. In addition, it
is important to maintain correct
calibration on a regular basis.
Comparison ofthe Mark 25 to a referee
system is the preferred method of
validation, however, calibration using
the Mark 25’s internal circuitryis also
acceptable.
In the event a problem develops with
the Mark 25 that cannot be resolved
through calibration or maintenance,
contact Martek Instruments directlyvia
telephone, fax, or e-mail located at our
website, ww.martekinstruments.com.

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