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Instruction Manual
Corning Model 312 Portable Dissolved Oxygen Meter
This manual contains complete instructions for
setting up and using the Corning Model 312
Portable Dissolved Oxygen Meter.
The information contained in this manual was
correct at the time of going to print. However, we
continue to improve products and reserve the right
to change specifications, equipment and
maintenance procedures at any time.
This manual is copyrighted, and all rights are
reserved. No part of this manual may be
reproduced by any means or in any form without
prior consent in writing.
CB.015.98 ©1998 Corning Incorporated
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Instruction Manual
Corning Model 312 Portable Dissolved Oxygen Meter
Contents
1 Set Up
1.1 Unpacking and Installation 3
1.2 Product Description 3
1.3 Functional Description 4
1.4 Initial Probe Preparation 5
2 Operation
2.1 Calibration 6
2.2 Measurements 6
2.3 Altitude Compensation 7
2.4 NaCl Compensation 7
3 Support Information
3.1 Probe and Membrane Maintenance 8
3.2 Battery Replacement 9
3.3 Specifications 9
Consumables/Accessories 10
Warranty 10
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Instruction Manual
Corning Model 312 Portable Dissolved Oxygen Meter
1.1 Unpacking and Installation
1. Unpack the meter and examine it to make
sure that no damage has occurred during
shipping. If there is any damage, notify your
distributor immediately.
2. In addition to this manual, you will find the
following items:
Meter w/Wrist Strap 1
DO Probe (476611) 1
Carry Case (470442) 1
Membrane Caps (473730) 3
Membrane Fill Solution
(30 ml Sample Bottle) 1
Warranty Card 1
Guide to Conductivity and
Dissolved Oxygen (470439) 1
9V Battery (471027) 1
Calibration Trimmer Screwdriver 1
3. Save all packing material until you are sure
that the instrument functions correctly. Any
defective or damaged items must be returned
in the original carton with the supplied
accessories.
4. Fill in and return the warranty card. For your
own record make a note of the serial number,
date of purchase and supplier on page 10 of
this manual.
1.2 Product Description
The Corning Model 312 is a water resistant,
micro-processor-based Dissolved Oxygen Meter
with automatic temperature compensation. It has
been developed for dissolved oxygen
measurements in water and waste water
applications as well as other applications such as
fish farming.
Dissolved oxygen is displayed in milligrams/litre
(mg/l).
The displayed value is compensated for changes
in solubility of oxygen in water and for permeability
of the membrane as well as temperature.
One 9V Alkaline battery provides power and
makes the instrument completely portable. A
microprocessor is used for accurate and rapid
calibration measurement.
The dissolved oxygen probe has a membrane
covering the polargraphic sensors and a built-in
thermistor for temperature measurements and
compensation. The thin permeable membrane
isolates the sensor elements from the testing
solution, but allows the oxygen to enter. When a
voltage is applied across the sensor, oxygen that
has passed through the membrane reacts causing
the current to flow.
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Instruction Manual
Corning Model 312 Portable Dissolved Oxygen Meter
1.3 Functional Description
Model 312
1 Probe Connector
2 Zero Oxygen Trimmer
3 LOW BAT Indicator
4 on/off Button
5 100% Oxygen Trimmer
6 Calibration Trimmer Housing
1
2
5
3
6
7
13
7 Liquid Crystal Display
8 cal Button
(to enter or exit calibration mode)
9 temp Button
(to enter or exit temperature mode)
10 Battery Compartment
11 O-Ring Seal
12 Silver Chloride Anode (sensor)
13 Water Resistant Shielded Cable
14 Polypropylene Probe Body
15 Temperature Sensor
16 Platinum Cathode (sensor)
17 Membrane Cap
18 Oxygen Permeable Teflon Membrane
19 Protective Cap
4
8
14
9
15
11
12
17
16
18
10
19
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Instruction Manual
Corning Model 312 Portable Dissolved Oxygen Meter
1.4 Initial Probe Preparation
All probes are shipped in a dry state. To hydrate
the probe and prepare it for use, connect it to the
meter and proceed as follows:
1. Remove the plastic black and red cap. This
cap is for shipping purposes and can be
thrown away.
2. Wet the sensor by soaking the bottom 20mm
of the probe in electrolyte (473731) for 5
minutes.
3. Rinse the membrane (473730 - supplied in the
kit with the meter) with electrolyte while
shaking it gently. Refill with clean electrolyte.
4. Gently tap the sides of the membrane cap with
your finger tip to ensure that no air bubbles
remain. To avoid damaging the membrane, do
not tap the membrane directly on the bottom.
5. With the sensor facing down, firmly screw the
cap clockwise to the end of the threads. Some
electrolyte will overflow.
When not in use, place the transparent
protective cap supplied in the kit with the
meter.
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Instruction Manual
Corning Model 312 Portable Dissolved Oxygen Meter
2.1 Calibration
The instrument has to be calibrated every time
it is turned on. This operation is very simple
and fast.
Proceed as follows (calibration at sea level):
l Ensure the probe is ready for measurements
(see Initial Preparation on page 5). The
membrane should be filled with electrolyte, the
probe connected to the meter and the
transparent protective cap removed.
l Switch the meter on. For an accurate
calibration, it is recommended that you wait 5
or 10 minutes to ensure precise conditions of
the probe.
l Remove the protective cap (19 in the
Functional Description, page 4) from the D.O.
Probe.
Zero Oxygen Calibration:
l Dip the electrode into zero oxygen solution
(473625 or 473739).
l Press cal to change display to % Saturation.
l Allow 2 minutes for the LCD to stabilize.
l Adjust the zero oxygen trimmer until the
display reads 0.0.
Slope Calibration:
l Rinse the electrode in a large amount of clean
water to remove any residual zero oxygen
solution.
l Blot the electrode tip dry and allow a few
minutes for the LCD to stabilize.
l Adjust the slope trimmer on the top of the
meter to read 100% on the LCD.
l Press the cal button and the LCD will return to
mg/I of oxygen.
l The instrument must be recalibrated
whenever the probe, membrane or electrolyte
are changed.
l If you want to exit the calibration mode during
calibration, press cal.
NOTE:
The zero calibration of the Model 312 is very
stable and therefore, the zero calibration
procedure need only be performed whenever the
probe is replaced. However, because the slope
calibration is critical relative to the usage, it is
recommended that the procedure is repeated
every time the meter is turned on.
2.2 Measurements
Ensure the meter has been calibrated.
Press on, remove the transparent protective cap
and immerse the tip of the probe in your sample.
Ensure the temperature sensor is also immersed.
When the reading has stabilized, record the value.
NOTE:
For accurate dissolved oxygen measurements, a
water movement of about 1 meter every 3
seconds is required. This is to ensure that the
oxygen-depleted membrane surface is constantly
replenished. A moving stream will provide
adequate circulation.
During field measurements, this condition may be
met by manually agitating the probe within the
solution being measured. Accurate readings are
not possible while the liquid is at rest. During
laboratory measurements, the use of a magnetic
stirrer to ensure a certain velocity in the fluid is
recommended. In this way, errors due to the
diffusion of the oxygen present in the air in the
solution are reduced to a minimum.
The Model 312 displays oxygen at sea level.
Compensation for salinity and altitude are not
automatic and therefore the readout values should
be corrected using the charts in Sections 2.3 and
2.4.
To display temperature press the temp button.
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Corning Model 312 Portable Dissolved Oxygen Meter
2.3 Altitude Compensation
Below is the chart showing correction factors for
Altitude Compensation. Locate your altitude and
the corresponding correction factor. Use the
example below to compensate for altitude.
Example: Meter displays 6.95 ppm on sample at
an altitude of 1000 m. Refer to chart and correct.
6.95 ppm x .88 = 6.12 ppm
Altitude Atmospheric Correction
(Meters) Pressure (Kpa) Factor
Sea level 101.3 1.00
50 100.7 .99
100 100.1 .99
150 99.4 .98
200 98.8 .98
300 97.6 .96
400 96.4 .95
500 95.2 .94
600 94.0 .93
700 92.8 .92
800 91.7 .90
900 90.5 .89
1000 89.4 .88
1100 88.3 .87
1200 87.2 .86
1300 86.1 .85
1400 85.0 .84
1500 84.0 .83
1600 82.9 .82
1700 81.9 .81
1800 80.9 .80
1900 79.9 .79
2.4 NaCl Compensation
Below is the chart showing the influence of salt in
the oxygen measurement. Determine the
temperature of your sample and the
corresponding quantity to be subtracted per g/l of
NaCl. Use the example below to compensate for
salinity.
Example: Meter displays 6.95 ppm at 20°C and
sample has a salinity of 15 g/l. Refer to chart for
correction factor (.0478).
6.95 ppm - (0.0478 x 15 g/l) = 6.23 ppm
Quantity to be Quantity to be
Subtracted per Subtracted per
°C g/l of NaCl °C g/l of NaCl
0 0.0892 26 0.0410
1 0.0861 27 0.0400
2 0.0830 28 0.0391
3 0.0802 29 0.0382
4 0.0779 30 0.0373
5 0.0749 31 0.0364
6 0.0724 32 0.0356
7 0.0701 33 0.0348
8 0.0678 34 0.0341
9 0.0657 35 0.0333
10 0.0637 36 0.0326
11 0.0618 37 0.0319
12 0.0599 38 0.0312
13 0.0582 39 0.0306
14 0.0565 40 0.0299
15 0.0549 41 0.0293
16 0.0533 42 0.0287
17 0.0519 43 0.0281
18 0.0505 44 0.0275
19 0.0491 45 0.0270
20 0.0478 46 0.0265
21 0.0466 47 0.0259
22 0.0454 48 0.0254
23 0.0442 49 0.0249
24 0.0431 50 0.0244
25 0.0421
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Instruction Manual
Corning Model 312 Portable Dissolved Oxygen Meter
3.1 Probe and Membrane Maintenance
The oxygen probe body is made of reinforced
plastic for maximum durability.
A thermistor temperature sensor provides
temperature compensation for the solution being
tested. It is always recommended that the
protective cap be kept on when the probe is not in
use to provide protection against damage and dirt.
To replace the membrane or refill with electrolyte,
proceed as follows:
l Remove the protective cap by gently twisting
and pulling it off the body of the probe (see
Fig. 2).
l While holding the probe in one hand, unscrew
the membrane by turning it counter-clockwise
with the other hand (see Fig. 1).
l Wet the sensor by soaking the bottom 25mm
of the probe in electrolyte for 5 minutes.
l Rinse the new membrane supplied with the
meter with electrolyte while shaking it gently.
Refill with clean electrolyte.
l Gently tap the sides of the membrane with your
finger tip to ensure that no air bubbles remain.
Do not directly tap the bottom with your finger as
this will damage the membrane.
The Platinum cathode (16 in the Functional
Description on page 4) should always be bright
and untarnished. If it is tarnished or stained, which
could be due to contact with certain gases or
extended use with a loose or damaged
membrane, the cathode should be cleaned. You
can use a fiberglass brush, clean lint-free
cardboard or cloth. Rub the cathode gently side to
side to polish and remove any stains. Afterwards,
rinse the probe with deionized or distilled water
and install a new membrane cap using fresh
electrolyte and follow the steps above.
Important: In order to have accurate and stable
measurements, it is important that the surface of
the membrane is in perfect condition. This semipermeable membrane isolates the sensor
elements from the environment but allows oxygen
to enter. If any dirt is observed on the membrane,
rinse carefully with distilled or deionized water. If
any imperfections still exist, or any damage is
evident (such as wrinkles or tears - holes are
evident by KCI formation), the membrane should
be replaced. Be sure that the O-Ring is properly
sealed in the membrane cap.
l With the sensor facing down firmly screw the
membrane cap clockwise to the end of the
threads. Some electrolyte will overflow.
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Corning Model 312 Portable Dissolved Oxygen Meter
3.2 Battery Replacement
When battery power becomes low, the LCD will
display a V in the upper left corner. At this point
the meter has approximately 25 hours of power
remaining.
To replace the battery simply remove the two
screws holding the cover and take out the battery.
Replace with a new 9V battery paying attention to
the indicated polarity.
3.3 Specifications
Range 0.0 to 19.9 mg/l
0 to 60°C
Resolution 0.1 mg/l
1°C
Accuracy ±1.5% of full scale, 1°C
Calibration 0 and 100% with trimmers
(manual)
Temperature Automatic from 0 to 30°C
Compensation (32 to 86°F)
Operating From 0 to +50°C (+32 to +122°F)
Conditions Humidity: 100%
Battery 9V 100 hours continuous use
Dimensions 190L x 84W x 43D
(mm)
Weight (g) 340
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Instruction Manual
Corning Model 312 Portable Dissolved Oxygen Meter
Consumables/Accessories
476611 Dissolved Oxygen Probe w/4m Cable
473730 DO Membrane Caps (3 per pack) and
Fill Solution, 30 ml
473625 Zero Oxygen Standard, 500 ml
473739 Zero Oxygen Sachets, 30 per pack
470442 Carrying Case
470439 Guide Book to Dissolved Oxygen &
Conductivity
Warranty
Corning warrants this product to be free from
defects in materials and workmanship. The
warranty period for the meter is one (1) year from
the date of purchase and the probe is six (6)
months from the date of purchase.
This instrument is in compliance with the CE
directives EN 50081-1 and EN 50082-1.
For your reference, make a note of the serial
number, date of purchase and supplier here.
Serial No . ..............................................................
Date Purchased .....................................................
Supplier ..................................................................
Corning Incorporated
Science Products Division
Big Flats Plant, New York 14831, USA
Tel: +1 800 222 7740 or +1 607 974 0353
www.corninglabware.com
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