USER MANUAL
MI 605
Portable
Dissolved Oxygen Meter
MANMI605 06/04
2
TABLE OF CONTENTS
Specifications ........................................................... 3
Accessories ............................................................. 3
Initial operations ....................................................... 4
Probe preparation .....................................................4
Probe polarization .................................................... 5
Measurements ......................................................... 5
Altitude compensation .............................................. 7
Salinity compensation .............................................. 8
Calibration procedure ............................................... 9
Probe & membrane maintenance ........................... 10
Battery replacement................................................ 11
WARRANTY
This instrument is warranted against defects in materials
and manufacturing for a period of two years from the date
of purchase. Probe is warranted for 6 months. If during
this period the repair or replacement of parts is required,
where the damage is not due to negligence or erroneous
operation by the user, please return the parts to either
distributor or our office and the repair will be effected free
of charge.
Damages due to accidents, misuse, tampering or lack of
prescribed maintenance are not covered.
11
If the Platinum cathode is tarnished or stained, which could
be due to contact with certain gases or to an extended use
with a loose or damaged membrane, it should be cleaned.
Use a clean lint-free cloth and rub the cathode very gently
side to side 4-5 times. This will be enough to polish it and
remove any stains without damaging the Platinum tip.
Afterwards, rinse the probe with deionized or distilled
water and install a new membrane cap using fresh electrolyte and follow the steps above. Recalibrate the instrument.
Note: To obtain accurate and stable measurements, it is
important that the surface of the membrane be in
perfect condition. This semipermeable membrane iso-
lates the sensor elements from the environment, but
allows oxygen to enter. If any dirt is observed on the
membrane, rinse it carefully with distilled or deionized
water. If any imperfections still exist, or any damage
is evident (such as wrinkles or tears-holes), replace
the membrane. Make sure that the O-Ring is properly
seated in the membrane cap.
Note: If don’t take measurements for a few hours, protect the
probe with the supplied cap.
BATTERY REPLACEMENT
When the battery becomes weak, the meter will display the
blinking battery symbol to indicate that only about 10 hours of
battery life remain. A low battery will result in unreliable
measurements. It is recommended to replace the battery
immediately by using an alkaline 9V battery.
Turn the meter off, unscrew the two screws on the rear of the
instrument, remove the cover and replace the 9V battery
with a new one. Install the battery while paying attention to
its polarity and reattach the cover.
3
SPECIFICATIONS
RANGE 0.0 to 45.00 mg/L (ppm) O
2
0.0 to 300 % O
2
0.0 to 50.0 °C
RESOLUTION 0.01 mg/L (ppm) O2 / 0.1 %O
2
0.1 °C
ACCURACY ± 1.5% F.S. (mg/L O2 / %O2)
(@25°C) ± 0.5 °C
TYPICAL EMC ± 0.3 mg/L (ppm) O2 / ± 3.5 %O
2
DEVIATION ± 0.5 °C
CALIBRATION Automatic in saturated air
TEMPERATURE COMPENSATION
Automatic, from 0 to 50°C
ALTITUDE COMPENSATION
0 to 4000 m; 100 m resolution
SALINITY COMPENSATION
0 to 80 g/L; 1 g/L resolution
PROBE MA840 (included)
ENVIRONMENT 0 to 50°C; 100% RH max.
BATTERY TYPE 1 x 9V alkaline (included)
BATTERY LIFE approx. 100 hours of use
AUTO-OFF after 4 hours of non-use
DIMENSIONS 200 × 85 × 50 mm
WEIGHT 280 g (with battery)
ACCESSORIES
MA840 D.O. probe
MA841 Spare membrane, 5 pcs
MA9071 Refilling Electrolyte solution, 230 ml
10
PROBE & MEMBRANE MAINTENANCE
The D.O. probe body is made of reinforced plastic for
maximum durability.
A thermistor temperature sensor provides temperature measurements of the tested sample. It is always recommended
to keep the protective cap on the probe when not in use, to
protect it against damage and dirt.
To replace the membrane or refill it with electrolyte,
proceed as follows:
• Remove protective cap by gently twist-
ing and pulling it off the probe's body.
• Unscrew the membrane by turning it
counterclockwise with the other hand.
• Wet the sensor by soaking the bottom
2.5 cm of the probe in electrolyte
(MA9071) for 5 minutes.
• Rinse new membrane supplied with meter
with electrolyte, while shaking it gently.
Refill with clean electrolyte.
• Gently tap the sides of the membrane
with the finger tip to ensure that no air
bubbles remain trapped. Do no directly
tap the bottom with the finger as this will
damage the membrane.
• Make sure that the rubber
O-ring is seated properly
inside the membrane cap.
• With the sensor facing
down, screw the membrane
cap clockwise. Some electrolyte will overflow.
TWIST
AND
PULL
UNSCREW
4
PROBE PREPARATION
D.O. probes are shipped dry. To hydrate the probe and
prepare it for use, connect it to the meter and proceed as
follows.
1. Remove the red and black plastic cap.
This cap is used for shipping purposes
only and can be thrown away.
2. Wet the sensor by soaking the bottom 2.5
cm of the probe in electrolyte (MA9071)
for 5 minutes.
3. Rinse the membrane (supplied
with the meter) with electrolyte
while shaking it gently. Refill
with clean electrolyte.
4. Gently tap the sides of the
membrane with the finger tip to
ensure that no air bubbles re-
main trapped. To avoid dam-
aging the membrane, do not
tap the membrane directly on
the bottom.
5. Place rubber O-Ring properly inside the membrane cap.
6. With the sensor facing down, screw the cap clockwise.
Some electrolyte will overflow.
When not in use and during polarization, place the protective cap supplied with the meter.
THEN SCREW
BACK ON
THIRD
TAP
SECOND
FILL
FIRST
INSERT
O’RING
Shipping
cap
black
red
INITIAL OPERATIONS
The meter is supplied with a 9V battery. Remove the
battery compartment cover on the back of the meter and
install the battery while paying attention to its polarity.
9
CALIBRATION PROCEDURE
Calibration is simple and is recommended every time the
meter is switched on.
• Make sure the probe is ready for measurements (see
Probe Preparation), i.e. the membrane is filled with
electrolyte and the probe is connected to the meter and
properly polarized.
• Switch the meter on by pressing the ON/OFF key.
• The "COND" message will be dis-
played for about 45 sec. to inform the
user that the probe is in auto-condition-
ing mode (automatic polarization) .
• Once “COND” disappears, the probe
is polarized and the instrument can be
calibrated.
• Remove the probe protective cap.
• Press CAL. "----" appears on the
larger LCD together with "CAL" to
indicate that the instrument is in cali-
bration mode.
• The instrument will automatically stan-
dardize itself to the actual saturation
value. After approx. 1 minute it will
display "100%" to indicate that the
calibration is complete.
Notes:
• It is recommended to re-calibrate the meter when-
ever probe, membrane or electrolyte is changed.
• To exit the calibration mode, press CAL.
• Switching from readings in % O2 to readings in mg/
L does not require recalibration.
5
PROBE POLARIZATION
The probe is under polarization with a fixed voltage of
approximately 800 mV.
Probe polarization is essential for stable measurements
with the same recurring degree of accuracy.
With the probe properly polarized, oxygen is continually
"consumed" by passing through the sensitive diaphragm
and dissolving in the electrolyte solution inside the probe.
If this operation is interrupted, the electrolyte solution con-
tinues to be enriched with oxygen until it reaches an
equilibrium with the surrounding solution.
Whenever measurements are taken with a non-polarized
probe, the oxygen level indicated is both that of the test
solution as well as that present in the electrolyte solution.
This reading is obviously incorrect.
MEASUREMENTS
Make sure the meter has been calibrated
and the protective cap has been removed.
Immerse the tip of the probe in the sample
to be tested while ensuring that also the
temperature sensor is immersed.
For accurate dissolved oxygen measurements, a water
movement of at least 0.3 m/sec is required. This is to
ensure that the oxygen-depleted membrane surface is
constantly replenished. A moving stream will provide an
adequate circulation. To quickly check if the water speed
is sufficient, wait for the reading to stabilize and then move
the D.O. probe. If the reading remains stable, the measurement conditions are right, while if the reading increases
the water movement is not adequate.
8
SALINITY COMPENSATION
To enter salinity compensation, press the FACTOR key
twice and the “SALT FACTOR” message will be displayed. Use UP and DOWN keys to set the salinity
between 0 and 80 g/L.
The meter will automatically compensate for salinity effects
(see also following table for verification).
35 g/l
9.0
8.6
8.3
8.0
7.6
7.4
7.1
6.9
6.6
6.4
30 g/l
9.3
8.9
8.6
8.2
7.9
7.6
7.3
7.1
6.8
6.6
°C
10
12
14
16
18
20
22
24
26
28
0 g/l
11.3
10.8
10.3
9.9
9.5
9.1
8.7
8.4
8.1
7.8
10 g/l
10.6
10.1
9.7
9.3
8.9
8.5
8.2
7.9
7.6
7.4
20 g/l
9.9
9.5
9.1
8.7
8.4
8.0
7.8
7.5
7.2
7.0
°F
50.0
53.6
57.2
60.8
64.4
68.0
71.6
75.2
78.8
82.4
Salinity (g/l) at Sea Level
6
During field measurements, this condition may be met by
manually agitating the probe. 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.
Anyway, wait the time necessary for thermal equilibrium
to occur between the probe and the sample (a few minutes
for temperature difference of several degrees).
The meter can display D.O. readings in
mg/L (ppm) and in % O
2
(rate of Oxy-
gen saturation with reference to 100% at
sea level). Press the RANGE key to
select the desired range.
The temperature measurement is always
displayed on the lower part of the LCD.
If the sample contains salts or if the measurement is
performed at altitude different from sea level, the readout
values must be corrected, taking into account the lower
degree of oxygen solubility.
Set altitude and salinity compensations before performing
calibration and taking measurements. The meter will automatically compensate for these factors.
7
ALTITUDE COMPENSATION
To enter altitude compensation, press the FACTOR key
and the meter will display the “ALT FACTOR” message.
Use UP and DOWN keys to set the altitude from 0 to 4.0
km, in steps of 0.1 km.
The meter will automatically compensate for altitude (see
also the table below for verification).
°C
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
0
m
14.6
13.8
13.1
12.4
11.8
11.3
10.8
10.3
9.9
9.5
9.1
8.7
8.4
8.1
7.8
7.5
7.3
7.1
6.8
6.6
6.4
300
m
14.1
13.3
12.7
12.0
11.4
10.9
10.4
9.9
9.7
9.2
8.8
8.4
8.1
7.8
7.5
7.2
7.1
6.9
6.6
6.4
6.2
600
m
13.6
12.9
12.2
11.6
11.0
10.5
10.1
9.6
9.2
8.7
8.5
8.1
7.8
7.5
7.3
7.0
6.8
6.6
6.3
6.2
6.0
1500
m
12.3
11.6
11.0
10.4
9.9
9.5
9.1
8.7
8.3
8.0
7.7
7.3
7.1
6.8
6.6
6.3
6.1
6.0
5.7
5.6
5.4
1800
m
11.8
11.2
10.6
10.1
9.6
9.2
8.8
8.3
8.0
7.7
7.4
7.1
6.8
6.6
6.3
6.1
5.9
5.8
5.5
5.4
5.2
900
m
13.2
12.4
11.9
11.2
10.6
10.2
9.7
9.3
8.9
8.6
8.2
7.8
7.5
7.3
7.0
6.8
6.6
6.4
6.1
5.9
5.8
Altitude, Meters above Sea Level
°F
32.0
35.6
39.2
42.8
46.4
50.0
53.6
57.2
60.8
64.4
68.0
71.6
75.2
78.8
82.4
86.0
89.6
93.2
96.8
100.4
104.4
1200
m
12.7
12.0
11.4
10.8
10.3
9.8
9.4
9.0
8.6
8.3
7.9
7.7
7.3
7.0
6.8
6.5
6.4
6.2
5.9
5.7
5.6
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