YSI 58 User Manual

YSI 58

Dissolved Oxygen Meter

Operations Manual

SECTION 1 INTRODUCTION .......................................................................................................................1

SECTION 2 PREPARING THE METER......................................................................................................2

2.1 UNPACKING ..............................................................................................................................................2

2.2 WARRANTY CARD.................................................................................................................................. 2

2.3 BATTERIES................................................................................................................................................. 2

SECTION 3 PREPARING THE PROBE.......................................................................................................3

3.1 CHOOSING THE CORRECT PROBE...................................................................................................... 3

3.1.1 YSI 5239 DO FIELD PROBE ...........................................................................................................3

3.1.2 YSI 5905 BOD PROBE .....................................................................................................................3

3.1.3 YSI 5739 DO PROBE........................................................................................................................ 4

3.1.4 YSI 5718 DO FIELD PROBE ...........................................................................................................4

3.1.5 YSI 5750 BOD BOTTLE PROBE ....................................................................................................4

3.2 PROBE INSTALLATION - YSI 5739.......................................................................................................5

3.3 CHOOSING THE CORRECT MEMBRANE........................................................................................... 5

3.3.1 MEMBRANE INSTALLATION FOR THE 5239 PROBE............................................................ 6

3.3.2 MEMBRANE INSTALLATION FOR THE 5905 PROBE............................................................ 7

3.3.3 MEMBRANE INSTALLATION FOR THE 5700-SERIES PROBES........................................... 8

SECTION 4 OPERATION.............................................................................................................................. 10

4.1 PRINCIPLES OF OPERATION............................................................................................................... 10

4.2 TURNING THE INSTRUMENT ON...................................................................................................... 11

4.3 CALIBRATION......................................................................................................................................... 11

4.3.1 AIR CALIBRATION....................................................................................................................... 12

4.3.2 WINKLER TITRATION................................................................................................................. 13

4.3.3 AIR-SATURATED WATER CALIBRATION............................................................................. 13

4.3.4 CALIBRATION FREQUENCY .....................................................................................................14

4.4 MAKING MEASUREMENTS................................................................................................................. 14

4.4.1 ENVIRONMENTAL CONSIDERATIONS..................................................................................14

4.4.2 MEASURING OXYGEN IN FLUIDS OTHER THAN WATER................................................ 15

4.4.3 CALIBRATING TO DISPLAY OXYGEN PARTIAL PRESSURE IN MM HG.......................15

4.5 RECORDER OUTPUT.............................................................................................................................16

SECTION 5 CARE AND MAINTENANCE................................................................................................17

5.1 THE METER CASE.................................................................................................................................. 17

5.2 PROBE PERFORMANCE CHECK......................................................................................................... 17

5.3 PROBE PRECAUTIONS..........................................................................................................................17

5.3.1 5905 AND 5239 PROBE CARE .....................................................................................................18

5.3.2 5700-SERIES PROBE CARE..........................................................................................................19

5.4 PROBE STORAGE...................................................................................................................................19

5.4.1 5905 AND 5239 PROBE STORAGE............................................................................................. 19

5.4.2 5700 SERIES PROBE STORAGE.................................................................................................. 19

SECTION 6 DISCUSSION OF MEASUREMENT ERRORS.................................................................. 20

SECTION 7 TROUBLESHOOTING............................................................................................................ 21

SECTION 8 WARRANTY AND SERVICE INFORMATION................................................................ 23

APPENDIX A GENERAL SPECIFICATIONS......................................................................................... 28

APPENDIX B REQUIRED NOTICE .........................................................................................................30

APPENDIX C ACCESSORIES AND REPLACEMENT PARTS...........................................................31

APPENDIX D UNIT CONVERSION CHART..........................................................................................32

APPENDIX E OXYGEN SOLUBILITY TABLE..................................................................................... 33

APPENDIX F CALIBRATION VALUES TABLE..................................................................................35

SECTION 1 INTRODUCTION

The YSI 58 Dissolved Oxygen Meter is intended for field or laboratory use for dissolved oxygen and temperature measurement and water, but is also suitable for use in certain other fluids. See Section

4.4.2, Measuring Oxygen in Fluids Other than Water. The meter may be used with the YSI 5239 probe, 5905 probe or the 5700 Series probes.

Dissolved oxygen is displayed in mg/L (1 mg/L = 1 part per million) or in percent air saturation. The air saturation feature is discussed in detail in the next section. Display sensitivity in the mg/L mode may be selected to read in tenths to in hundredths of a mg/L.

Temperature is displayed in °C from -5 °C to +45 °C with 0.1°C resolution. The mg/L mode is automatically temperature compensated for changes in solubility of oxygen in water and for permeability of the probe membrane. A salinity compensation control allows direct determination for mg/L of dissolved oxygen in oceanic or estuarine waters.

The probes use Clark-type membrane covered polargraphic sensors with built-in thermistors for temperature measurement and compensation. A thin, permeable membrane stretched over the sensor isolates the sensor elements from the environment, but allows oxygen and certain other gases to enter. When a polarizing voltage is applied across the sensor, oxygen that has passed through the membrane reacts at the cathode, causing a current to flow.

The membrane passes oxygen at a rate proportional to the pressure difference across it. Since oxygen is rapidly consumed at the cathode, it can be assumed that the oxygen pressure inside the membrane is effectively zero. Hence, the force causing the oxygen to diffuse through the membrane is proportional to the absolute pressure of oxygen outside the membrane. If the oxygen pressure increases, more oxygen diffuses through the membrane and more current flows through the sensor. A lower pressure results in less current.

PERCENT SATURATION

The percent saturation feature of this instrument allows quick determination of the degree of air saturation occurring in fresh or saline water. This feature also allows measurement in fluids of unknown oxygen solubility.

The percent saturation displayed in this mode is the saturation that would occur if the sample were saturated with air under a normal barometric pressure of 1013 millibars (760 mm Hg or 29.92 inches Hg). Results reported from such measurements should be noted as air saturation, corrected to standard pressure.

This feature also makes possible a simple and quick calibration procedure that eliminates the need to determine exact probe temperature or to calculate the barometric pressure effect on the calibration value.

SECTION 2 PREPARING THE METER

2.1 UNPACKING

When you unpack your new YSI 58 Dissolved Oxygen and Temperature System for the first time, compare the packing list with the contents of the shipping box. If there is anything missing or damaged, contact your YSI dealer from whom you purchased the YSI 58 or YSI Customer Service at 800-765-4974 or 937-767-7241.

2.2 WARRANTY CARD

Please complete the Warranty Card and return it to YSI. The warranty card allows the entry of your purchase of this instrument in our computer system.

2.3 BATTERIES

Batteries provide complete portability; a battery eliminator feature bypasses the instrument batteries for extended line-powered use (not including stirrer). Instrument batteries are carried internally in one holder while a second holder allows internal installation of batteries for powering a submersible stirrer for use in the field.

Instrument batteries are in the upper holder. Four D-size carbon-zinc batteries are used. The LOBAT warning shows on the display when about 50 hours of use remain. This warning reminds the operator to change batteries at their earliest convenience. Batteries may be removed when the instrument will be used on a long-term basis for laboratory measurement powered by the YSI 5401 or 5402 battery eliminator.

Stirrer batteries fit in the lower battery holder. Four D-size carbon-zinc batteries are used. When about five hours or less of battery life remains, the LOBAT warning will show on the display when the STIRRER control is held at the spring-loaded BATT CHK position. Instrument must be turned

on. Batteries are needed only when the YSI 5795A Submersible Stirrer will be used.

YSI 5401 (115 VAC) AND 5402 (230 VAC) BATTERY ELIMINATORS

For exclusive or long-term laboratory use, the 5401 or 5402 Battery Eliminator may power the YSI

58. When the battery eliminator is in use, batteries may be removed from the instrument battery compartment (upper compartment).

Note: The battery eliminator does not power the 5795A Field Stirrer, which operates only when there are batteries in the stirrer battery compartment (lower compartment).

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SECTION 3 PREPARING THE PROBE

3.1 CHOOSING THE CORRECT PROBE

Five different YSI oxygen probes may be used with the YSI 58 Meter.

¾ YSI 5239 is designed for field use with cable lengths of 10, 25 or 50 foot. ¾ YSI 5905 is a self-stirring BOD bottle probe. ¾ YSI 5739 is designed for field use and may be used with or without a stirrer. A 5740 probe cable

or 5795A stirring cable is required for use with the 5739 probe. YSI 5795A has a dual-purpose cable to which both stirrer and probe are connected.

¾ YSI 5750 is a BOD bottle probe with no stirrer. ¾ YSI 5718 is designed for field use with no pressure compensation and has a permanently attached

cable.

3.1.1 YSI 5239 DO FIELD PROBE

The YSI YSI 5239 probe is used for measuring dissolved oxygen in the field. It features cap membranes for easy membrane replacement (YSI 5906 membrane caps). The probe is rugged, with the DO and temperature sensors enclosed in a heavy-duty probe guard. A 10, 25 or 50 foot cable is directly connected to the probe body making it waterproof. A 5-pin MS connector at the end of the cable makes the 5239 fully compatible with all YSI 50 series DO meters retaining the accuracy of the system. The 5239 has been optimized for YSI meters which have a microprocessor for sampling and processing data, such as YSIs 50B and 52.

NOTE: The 5239 probe is shipped dry. A shipping membrane was installed to protect the electrodes. A new membrane cap must be installed before first use.

3.1.2 YSI 5905 BOD PROBE

The YSI 5905 BOD (Biochemical Oxygen Demand) probe is used for measuring dissolved oxygen in all popular size BOD bottles. This probe features a self-stirring probe and an easily replaced membrane cap and a refurbishable electrode system.

IMPORTANT: Intended Use

The 5905 probe is intended for laboratory use, not field use. It is not waterproof and should never be

immersed past the taper on the stem of the probe.

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The 5905 probe is designed for use with all YSI dissolved oxygen meters, except for the YSI 55, 85 or YSI 95. The 5905 probe comes in several versions, designed to fit different bottle sizes.

5905

5905 - J

5905 - K

5905 - L

5905 - W

5° taper per side to fit U.S. Standard BOD bottles.

Includes an adapter to fit 5° taper per side smaller bottles with built - in overflow funnels.

Includes a s 19 funnel.

Includes a s 24 funnel.

6″ long probe for use with wine bottles.

3.1.3 YSI 5739 DO PROBE

For user convenience, the 5739 probe is equipped with a disconnecting cable to facilitate changing cable lengths and replacing damaged cables or probes. The probe and cable assembly is held together with a threaded retaining nut. The connection is not designed for casual disconnection and should only be disconnected when necessary. For sample stirring with the 5739 probe, the 5795A Submersible Stirrer has a dual-purpose cable to which both stirrer and probe are connected.

YSI 5795A SUBMERSIBLE STIRRER

The YSI 5795A Stirrer, which can only be used with the 5739 probe, features a single cable for both probe and stirrer to permit convenient manipulation and storage.

When a stirrer and probe are assembled, the stirrer agitates the sample directly in front of the sensor by means of a rotating eccentric weight that causes the spring-mounted, sealed motor housing to vibrate. An impeller on the end of the motor housing flushes the fluid being assayed across the sensor surface.

Figure 1

3.1.4 YSI 5718 DO FIELD PROBE

The YSI 5718 field probe has a permanently attached cable and no pressure compensation.

3.1.5 YSI 5750 BOD BOTTLE PROBE

The YSI 5750 probe is similar in design to the 5739, but has a tapered body designed to fit standard US BOD bottles. It does not have a stirrer or cap membranes. Agitation of the sample must be provided by other means, such as a magnetic stirrer.

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Four D-size carbon-zinc batteries that are housed in the lower battery compartment of the YSI 58 power the stirrer. When the stirrer will not be used for an extended period, these batteries should be removed from the instrument.

3.2 PROBE INSTALLATION - YSI 5739

To disconnect the cable, unscrew the retaining nut and slide it down the cable to expose the connector. Pull gently on the cable and connector until the connector comes away from the probe body.

To reassemble, inspect the connector and O-Ring for cleanliness. If the O-ring is frayed or damaged, remove it by squeezing it in the groove causing it to bulge, then roll it out of the groove and off of the connector. A replacement O-ring is supplied with the cable.

Push the connector into the probe body, rotating it until the two halves match up. A VERY LIGHT coating of silicone grease on the O-Ring will make reassembly easier.

CAUTION: DO NOT apply more than a light coating of grease, as it will attract dirt and particles that may compromise the seal of the O-ring.

Air trapped between the connector halves that may cause them to spring apart slightly is normal. Screw on the retaining nut, HAND TIGHTEN ONLY!

Note: If erratic readings are experienced, disconnect the cable and inspect for the presence of water. If water is present, dry out and reconnect, replacing the O-Ring.

Pressure Compensation

The vent on the side of the probe is part of a unique pressure compensating system that helps assure accurate readings at great depths of water. Pressure compensation is effective to 0.5% of reading with pressures to 100psi (230 feet water). The quantity of air bubbles trapped under the membrane determines how serious the pressure error will be, which is why proper preparation of the probe is essential. See Section 4, Operation. The system is designed to accommodate a small amount of trapped air and still function properly, but the amount should be kept to a minimum.

The compensating system normally does not require servicing and should not be taken apart. However, if electrolyte is leaking through the diaphragm or if there is an obvious puncture, the diaphragm must be replaced. A spare is supplied with the probe. Using a coin, unscrew the retaining plug and remove the washer and diaphragm, flush any salt crystals from the reservoir, install the new diaphragm (ridged side in), replace the washer and screw in the retaining plug.

3.3 CHOOSING THE CORRECT MEMBRANE

An extremely thin membrane increases O probe’s response; but it achieves this at the cost of ruggedness. The membrane normally used with the YSI 58’s probes is the 1 ml (.001”) membrane. This 1 ml membrane represents a compromise between quickness of response, and membrane strength and integrity.

For special circumstances, a 0.5 ml (.0005”) membrane is available. This half-thickness membrane hastens response at low temperatures and helps suppress background current at very low dissolved

2 permeability and probe signal current, and hastens a

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oxygen levels. When data is routinely collected with sample temperatures below 15°C and at DO levels below 20% air saturation, the low signal current resulting from the use if the standard membranes tends to magnify the probe’s inherent constant background signal. Using the high sensitivity membranes in this situation will decrease the percent error due to the probe’s background current.

For long-term monitoring situations only, a half-sensitivity, double-thickness 2 ml (.002”) membrane is available. Order the YSI Item # 5685 2 ml membrane, which includes membranes and electrolyte for the 5718 and 5739 probes.

A selector switch inside the YSI 58 modifies the circuit for the membrane in use. This switch must be set to the position corresponding to the membrane in use. Facing the back of the instrument, with the back cover removed, the switch will be found on the top, right corner of the main PC board. Its positions are labeled .5, 1 and 2 MIL. Also, See Section 4.4.2, Oxygen Measurements in Fluids Other Than Water, for use of this switch in special measurement circumstances.

Membrane life depends on usage. However, if the electrolyte is allowed to evaporate and an excessive amount of bubbles form under the membrane, or the membrane becomes damaged, thoroughly flush the reservoir with electrolyte and install a new membrane.

If erratic readings are observed or calibration is stable, you need to replace the membrane.

The gold cathode should always be bright and untarnished. If it is tarnished, which can result from contact with certain gases, or plated with silver, which can result from extended use with a loose or wrinkled membrane, return it to YSI for service. You can also clean the gold cathode with the YSI 5680 Probe Reconditioning Kit. Never use chemicals or any abrasive other that what is supplied with the kit. See Section 8 for contact information.

3.3.1 MEMBRANE INSTALLATION FOR THE 5239 PROBE

NOTE: The 5239 probe is shipped dry. A shipping membrane was installed to protect the electrodes. A new membrane cap must be installed before first use.

Follow the steps below to install a membrane cap:

1. Unscrew and rem ove the probe guard. See figure 2.

2. Unscrew the old m embrane cap and rem ove it from the probe.

3. Thoroughly rinse the entire area of the silver anode, gold cathode and threads with clean

water (distilled or deionized) to remove any dry crystals of the old electrolyte.

4. Hold the m embrane cap and fill it with 6 to 7 drops of YSI standard electrolyte (KCl probe

solution) provided.

5. Tap the bottom of the mem brane cap with your finger a few times (don’t touch the

membrane) to shake loose any trapped air bubbles.

6. Screw the m embrane cap onto the probe m oderately tight. A small amount of electrolyte

should overflow.

7. Rinse off the excess electrolyte with clean water.

8. Screw the probe guard onto the probe body.

9. Place the probe in the calibration bottle provided. Verify that sponge in the bottle is wet.

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Fill membrane cap with 6-7 drops of KCl solution. Tap cap with finger to remove bubbles.

Unscrew guard

Unscrew cap

Screw cap on moderately tight

Screw guard on Moderately tight

Figure 2

3.3.2 MEMBRANE INSTALLATION FOR THE 5905 PROBE

New Probe Use

New probes are shipped with a dry membrane cap to protect the electrodes. A new membrane

cap must be installed before first use.

Follow these instructions to change membrane caps:

1. Remove the stir paddle from the probe by pulling it straight out. See figure 3.

2. Unscrew the old membrane cap from the probe. Before installing a new membrane, clean the

probe tip with deionized water in order to remove any contaminants.

3. Hold the membrane cap and fill it at least half full with the electrolyte solution provided. Screw the

membrane cap onto the probe moderately tight. A small amount of electrolyte should overflow.

4. Rinse off excess electrolyte from the probe with deionized water.

5. Reinstall the stir paddle.

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Remove

Stir Paddle

Fill Membrane Cap

with Solution

Unscrew Cap

Replace

Stir Paddle

Screw Cap on

moderately tight

Figure 3

CHECKING THE PROBE ZERO

The probe zero is checked by immersing the probe in a sodium sulfite solution (0.08M or 3g Na

/300mL), or in water which has an inert gas bubbling through it (e.g. nitrogen, argon). The

2SO3

meter should read less than 1% dissolved oxygen in either of these environments. If it does not, change the membrane or clean the probe.

3.3.3 MEMBRANE INSTALLATION FOR THE 5700-SERIES PROBES

MEMBRANE INSTALLATION

All YSI 5700 Series Probes have similar sensors and should be cared for in the same way. They are precision devices and require careful treatment if measurements of high accuracy are to be made. Prepare the probe as described below.

WARNING: All probes are shipped dry, you must follow these instructions!

1. Open the membrane kit and prepare the electrolyte solution. Dissolve the KCl in the dropper bottle by filling it to the neck with deionized or distilled water and shaking until the solids are fully dissolved. After the KCL is dissolved, wait a few minutes until the solution is free of bubbles.

Remove the o-ring and the dry membrane from (after unscrewing the sensor guard. Thoroughly rinse the sensor with electrolyte fluid.

ADD DI OR DISTILLE

WATER

Figure

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