Hach sension 6 Instruction Sheet

Introduction

Specifications

51970-88

DISSOLVED OXYGEN PROBE

This instruction sheet provides information on the Hach Dissolved

™

Oxygen Probe for use with the sens

ion

The Dissolved Oxyge n Pro be is a Clar k-type amperomet ric se nsor us ed
to measure dissolved oxygen in aqueous solutions. It consists of an
anode/cathode electrode system and potassium chloride-based
electrolyte, separated from the sample by a replaceable oxygen­permeable Teflon membrane. A built-in thermistor provides automatic
temperature compensation when using the sens
Oxygen Meter.

6 Dissolved Oxygen Meter.

ion6 Dissolved

Dissolved Oxygen
Probe
1-meter cable

Warranty 1 year 1 year 1 year
Concentration Range 0 - 20 mg/L or

0 - 200% saturation

Accuracy ± 1.0% Full Scale ± 1.0% Full Scale ± 1.0% Full Scale
Temperature Range 0 - 50 °C 0 - 50 °C 0 - 50 °C
Response Time 99% of full value in

1 minute

Minimum Sample
Flow

Drift < 1%/day < 1%/day < 1%/day
Length 150 mm 150 mm 150 mm
Diameter 12 mm 12 mm 12 mm
Connector 5-pin circular 5-pin circular 5-pin circular
Weight Accessory Optional Optional Included

20 cm/sec 20 cm/sec 20 cm/sec

Dissolved Oxygen
Probe
3-mete r cable

0 - 20 mg/L or
0 - 200% saturation

99% of full value in
1 minute

Dissolved Oxygen
Probe
15-meter cable

0 - 20 mg/L or
0 - 200% saturation

99% of full value in
1 minute

DISSOLVED OXYGEN PROBE, continued
Assembly Instructions

1. Hold the membrane module cap in a vertical position.

2

2. Fill the module c ap about

Electrolyte Filling Solution, Hach Cat. No. 27591-26.

3. Hold the DO probe in a vertical position with the tip down and

gently screw the module cap onto the tip. Electrolyte should leak
out of the threads.

Note: If electrolyte does not leak out of the threads, air may remain inside the

module cap. To ensure accurate results, repeat this procedure using more
filling solution.

Attach the DO probe cable connector to the input connec tor at the top of
the meter. Refer to the sens
Manual for additiona l informatio n.

/3 of the way full wit h Dissolve d Oxygen

ion6 Dissolved Oxygen Meter Instruction

Using the Weight Assembly

The Weight Assembly is included with the probe equipped with the
15 m cable. Install the weight assembly as follows:

1. Remove the cap from the body of the weight.

2. Insert the probe into the body.

3. Slide the cap over the cable and thread the cap onto the body.

The weight will help to ensure that the probe travels straight down after
being placed in the w ate r and a lso p rotects the membr ane fro m da mage.

Zeroing the Probe

Chemically zeroing the probe is only necessary when measuring
dissolved oxygen at a level less than 1 ppm (or 10% saturation). When
measuring in this range, zero the probe prior to calibration. It is only
necessary to zero a probe once.

Refer to the sens
specific instructions.

ion6 Dissolved Oxygen Meter Instruction Manual for

2

DISSOLVED OXYGEN PROBE, continued
General Probe Operation

Follow the procedures presented in this section to obtain maximum
performance and accuracy from your DO probe:

• Use the DO probe only for aqueous applications.

• Take extra care when handling and storing the oxygen membrane

module cap.

• Do not allow the DO probe’s sensing area (cap reservoir) to dry out.

• Perform the calibration procedure at the beginning of each day for

maximum performance. Recalibrate the DO probe every two hours
for maximum accuracy.

The DO probe can be left out of solution for up to 24 hours without
damage. If the DO probe is not being used for more than 24 hours,
prevent electrolyte evaporation by storing it in the storage/calibration
chamber. Refer to the meter instru ction manu al fo r more inf ormati on on
probe storage.

Probe Polarization

Note: Prior to
operation , connect t he
probe to the meter.
Allow the probe to
stabilize for 30-50
minutes before
attempting
a calibration.

Hach dissolved oxygen probes are continuously polarized when they
are connected to the instrument. A steady reading will not be seen for

30–50 minutes when the probe is new or when it has been unplugged
for more than an hour. Interrupted connections of less than one hour
will require 5–25 minutes before stabilizing. Refer to the sens
Dissolved Oxyg en Meter Instruct ion Manual f or additiona l information.

Probe Calibration

Detailed instructions for calibrating the Dissolved Oxygen Probe using
a Water-saturated Air or Winkler Titration method are presented in the

sens

calibration procedure at the begin ning of eac h day for best performance.
Obtain maximum accuracy by recalibrating the probe every two hours.

ion6

ion 6 Dissolved Oxygen Meter Instruction Manual. Perform a

3

DISSOLVED OXYGEN PROBE, continued
Dissolved Oxygen Measurement

After the probe is properly stabilized, chemically zeroed (for
measurements below 1 mg/L), and calibr ated, take measurements
as follows:

1. Add the weight assembly to the probe if required (3 m or 15 m

cable versions only).

2. Insert the probe into the sample to the desired depth. Agitate the

probe in the sampl e to di slodg e air b ubbles from t he sen sing a rea of
the probe tip.

3. Stir the sample vigorously using the probe or a stir stand and stir

bar. When sampling bodies of water, create motion around the
probe tip by pulling on the cable to move the probe up and down
approximately 3-6 inches.

Storage

4. When the rea ding on the meter stabil izes, record the value or store

in meter memory.

To store the probe between measurements, insert the probe tip into the
provided Calibration/Storage Chamber containing deionized water.

To prepare the probe for long-term storage complete the following:

1. Disconnect the prob e from the meter.

2. Remove the membrane cap assembly.

3. Rinse the anode, cathode, and membrane cap assembly with

deionized water.

4. Shake the deionized water out of the membrane cap.

5. Use a clean lab wipe to blot the moisture from the electrode anode

and cathode.

6. Thread the membrane cap assembly loosely onto the body of

the probe.

4

DISSOLVED OXYGEN PROBE, continued
Maintenance

Membrane cap replacement and refilling are required at scheduled
intervals or if the probe does not function properly, e.g. in the case of a
damaged membrane or c ontaminated DO probe. If the me mb ran e i s not
damaged, the recommended time interval for replacing the Electrolyte
Filling Solution is 1-2 months.

Note: Hach supplies a
DO probe servi c e kit
that includes one
50-mL bottle of
Dissolved Oxygen
Electrolyte Filling
Solution, two
Membrane Modu le
Caps and a
Polishing cloth.

Prior to replacing a membrane cap, rub the anode (the outer, metallic
stem of the probe that is visible when the membrane cap is removed)
with the polishing cloth supplied with the probe. The polishing cloth
will remove deposits that may decrease the performance of the probe.
Polish the anode whenever the membrane cap is replaced or between
membrane cap replacements if the performance of the probe seems to
have degraded over time.

BOD Measurement

Adapt the Model 51970 Dissolved Oxygen Probe for BOD
measurements using the BOD Accessary Kit (Cat. No. 51971-00). The
kit includes a fun nel and spacer that fit th e M odel 519 70 DO Probe and
a standard 300 mL BOD bottle. The funnel has a stir bar incorporated
into the end which, when used with a stir stand, creates the proper
stirring motion required for BOD measurement. The spacer positions
the DO probe properly in the funnel. The funnel allows for sample
displacement with insertion of the DO probe and limits exposure to
atmospheric oxygen. Consult the sens
Instruction Manual for more information.

ion6 Dissolved Oxygen Meter

Barometric Pressure Correction

The values presented in Table 1 are based on the assumption that the
barometric pressure at sea level is 760 mm Hg. Use Table 1 to
determine the barometric pressure at specific elevations or obtain the
current barometric pressure from a local weather service. See the

sens
calibration instructions when using Table 1.

ion6 Dissolved Oxygen Meter Instruction Manual for specific

5

DISSOLVED OXYGEN PROBE, continued

Table 1 Elevation Barometric Pressure

Elevation

in feet

0 0 760 6000 1829 613

500 152 746 6500 1981 601
1000 305 733 7000 2134 590
1500 457 720 7500 2286 579
2000 610 708 8000 2438 568
2500 762 695 8500 2591 559
3000 914 683 9000 2743 548
3500 1067 671 9500 2896 538
4000 1219 659 10000 3048 527
4500 1372 647 10500 3200 517
5000 1524 635 11000 3353 506
5500 1676 624

Elevation
in meters

Barometric

pressure in

mm Hg

Elevation

in feet

Elevation
in meters

Barometric

pressure in

mm Hg

Replacement Parts and Accessories

BOD Accessory Kit (includes funnel and spacer for DO probe 51970) ......................51971-00

Bottle, BOD w/stopper, 300-mL.......................................................................................621-00

Calibration and Storage Chamber.................................................................................51974-00

DO Probe Service Kit (includes DO Electrolyte Filling

Solution, two Membrane Module Caps, and Polishing cloth)...................................51968-00

Electrode Holder w/Electromagnetic Stirrer, 115 V.....................................................45300-01

Electrode Holder w/Electromagnetic Stirrer, 230 V (without plug) .............................45300-02

Filling Solution, 50 mL.................................................................................................27591-26

Replacement Membranes, 2/pkg...................................................................................51973-00

Weight Assembly for the DO Probe.............................................................................51969-00

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© Hach Company, 1999. All rights reserved. Printed in the U.S.A. dd/dk 2/99 1ed