YSI Model 52 User manual

YSI Model 52
Dissolved Oxygen Meter
Operations
Manual

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CONTENTS
SECTION 1 INTRODUCTION......................................................................................1
1.1 Principles of Operation..................................................................................................................... 1
1.2 Display and Function Keys............................................................................................................... 2
1.3 Function Switch................................................................................................................................ 2
1.4 Power On Self Test (POST).............................................................................................................. 2
SECTION 2 PREPARING THE METER................................................................................................. 3
SECTION 3 CALIBRATION..................................................................................................................... 5
3.1 Percent and mg/L.............................................................................................................................. 5
3.2 Determining Calibration Value......................................................................................................... 5
3.3 Calibration in Air.............................................................................................................................. 6
3.4 Calibration in Air-Saturated Water................................................................................................... 7
3.5 Calibration by Winkler Titration ...................................................................................................... 7
3.6 Zero Calibration................................................................................................................................ 8
3.7 Resetting the Default Zero Calibration ........................................................................................... 10
SECTION 4 SALINITY ............................................................................................................................ 11
SECTION 5 OPERATION ....................................................................................................................... 13
5.1 Temperature Measurement ............................................................................................................. 13
5.2 Dissolved Oxygen Measurement .................................................................................................... 13
5.3 Measuring Oxygen in Fluids Other Than Water............................................................................. 13
5.4 Recording to Internal Memory........................................................................................................ 14
5.5 Reviewing Recorded Data .............................................................................................................. 15
5.6 Printing Data from Memory............................................................................................................ 16
5.7 Sending Recorded Data to a Personal Computer............................................................................ 16
5.8 Erasing the Model 52 Memory....................................................................................................... 17
SECTION 6 SYSTEM SETUP ................................................................................................................. 19
6.1 Setting the Time and Date............................................................................................................... 19
6.2 Setting Up Autostable..................................................................................................................... 19
6.3 Setting Communication Parameters................................................................................................ 21
6.4 Last Digit Suppression.................................................................................................................... 22
6.5 Contrast Adjustment ....................................................................................................................... 22
SECTION 7 PERSONAL COMPUTER INTERFACE.......................................................................... 25
7.1 Writing Your Own Applications Software...................................................................................... 25
SECTION 8 MAINTENANCE AND TROUBLESHOOTING.............................................................. 27
8.1 Batteries.......................................................................................................................................... 27
8.2 Power On Self Testing and Error Display Messages...................................................................... 27
SECTION 9 MEASUREMENT ERRORS .............................................................................................. 29
9.1 Type 1 Errors: Instrument Components.......................................................................................... 29
9.2 Type 2 Errors: Probe Accuracy ...................................................................................................... 29
9.3 Type 3 Errors: Calibration.............................................................................................................. 30

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9.4 Error Calculation Example ............................................................................................................. 30
SECTION 10 WARRANTY AND REPAIR............................................................................................ 32
APPENDIX A GENERAL SPECIFICATIONS...................................................................................... 39
APPENDIX B REQUIRED NOTICE...................................................................................................... 41
APPENDIX C OXYGEN SOLUBILITY ................................................................................................ 45
APPENDIX D CALIBRATION TABLES............................................................................................... 43

YSI, Incorporated Model 52 1
SECTION 1 INTRODUCTION
The YSI Model 52 is a microprocessor-based instrument designed for field and laboratory
measurement of dissolved oxygen. Readings are automatically compensated for
temperature. When calibrated to percent air saturation, the display simultaneously shows
dissolved oxygen in mg/L and in percent air saturation as well as temperature in degrees
Celsius.
An RS232 port permits results to be sent directly to your serial printer or personal
computer. Salinity compensation can be adjusted manually. To assure the highest
accuracy, an auto stable feature indicates when the readings have reached user-defined
criteria for stability. To assure correct operation, the meter performs a self-testing routine
each time it is turned on; any error is then signaled on the display.
Calibration is quick and easy. Procedures for calibrating with and without compensation
for temperature, altitude, pressure, and salinity are described in this manual. The YSI
Model 52 is also equipped with non-volatile memory, capable of storing up to 70 DO and
temperature readings. Any data stored in internal memory can be reviewed on the LCD,
or batch uploaded to a PC or an RS232 printer.
Power can be provided by an AC adapter (optional), or batteries that permit field use.
1.1 PRINCIPLES OF OPERATION
YSI dissolved oxygen probes use membrane covered, Clark-type polarographic 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
Oxygen diffuses through the membrane 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 zero. Hence, the amount of oxygen diffusing
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.

Introduction Section 1
YSI, Incorporated Model 52 2
1.2 DISPLAY AND FUNCTION KEYS
A rotary function switch and four keys provide complete control of the Model 52. The
four keys are SKIP,!,", and CONFIRM. !
!!
!and"are used to modify a setting
either up or down (for example, calibration or salinity values can be modified for each
calibration process if required). The CONFIRM key is used to accept your setting.
The display often asks questions such as “Calibrate in percent?” Use CONFIRM to
answer yes. Use SKIP to go on to the next choice. The SKIP key can also be used to
select among several default values.
1.3 FUNCTION SWITCH
The rotary function switch allows easy selection among the meter’s basic functions. In
O2-TEMP, the instrument is measuring dissolved oxygen and temperature. To begin
calibrating, switch to CALIBRATE. To begin setting the clock, communication, and
auto-stable parameters, switch to SYSTEM SETUP. EXTERNAL CONTROL activates
the RS232 port. Salinity can be set after switching to SALINITY.
1.4 POWER ON SELF-TEST
A Power On Self-Test (POST) takes place whenever the meter is turned on. This ensures
correct performance. If anything is wrong, the operator is signaled and the error
identified. An error message will appear on the display. For more information see Section
8.2, Power On Self-Testing and Error Display Messages.

YSI, Incorporated Model 52 3
SECTION 2 PREPARING THE METER
To prepare the meter for use, connect a prepared probe to the meter. Set the function
switch to O2-TEMP. Observe temperature and oxygen readings for stability, or see
section VIII.B to set up Autostable. Since complete equilibration can take as long as 15
minutes after the meter is turned on, it is customary to leave the instrument on throughout
the working day.
When the instrument is turned on, a beep signals the beginning of a Power On Self Test
(POST). A series of displays will appear. A final beep and a return to the normal display
signal the conclusion of the test. The whole process takes about 10 seconds. If the
instrument detects an error, it will display an error message. These messages, with
appropriate corrective actions, are listed in the Maintenance and Troubleshooting section
of this manual (see section X.B.). If you have a problem you cannot resolve, call YSI
Technical Support, [phone] or [phone].
Low Batt
Stirring: Since the oxygen level in the layer of liquid at the membrane surface is
continuously depleted, it is essential that water movement of 1 foot per second or more be
maintained while making dissolved oxygen measurements. When using the Model 52 in
field applications, a moving stream will usually provide adequate motion, as will moving
the probe through the sample by hand. For lab applications, we recommend one of the
YSI self-stirring BOD probes.
When the temperature and oxygen readings have stabilized, you are ready to begin
calibration.
6.33 mg/L 19.9C
88.1 % 11: 52

Preparing the Meter Section 2
YSI, Incorporated Model 52 4

YSI, Incorporated Model 52 5
SECTION 3 CALIBRATION
Calibration is accomplished by exposing the probe to a known concentration of oxygen
and then adjusting the calibration value to match. Since the oxygen content of our
atmosphere varies predictably according to relative humidity and atmospheric pressure,
we recommend that you calibrate in air, see Section 3.3, Calibration in Air.
Daily calibration is usually appropriate. Calibration can be disturbed by a physical shock,
touching the membrane, fouling of the membrane or drying out of the electrolyte. Check
calibration after each series of measurements, and in time you will develop a realistic
schedule for recalibration.
3.1 PERCENT AND MG/L
100 percent air saturation corrected to standard pressure is the dissolved oxygen value of
water saturated with air at 760 mm Hg (1013 millibars or 29.92 inches Hg). The mg/L
values describe the concentration of oxygen. Since calibrations in mg/L do not necessarily
yield correct percent readings, the percent readings are disabled after calibrations in mg/L.
Calibrations in percent are correct for both percent and mg/L readings.
3.2 DETERMINING CALIBRATION VALUE
Typically, local barometric pressure is not equal to "standard pressure." Therefore, unless
you are calibrating with a known sample determined by a Winkler titration, you should
determine the proper calibration point for the local barometric pressure. This corresponds
to a reading from a mercury barometer. Do not use the pressure reported by the Weather
Bureau that has been adjusted to sea level. The calibration value for a given barometric
pressure can be read from the chart on the back of the meter, or the one in Appendix B. of
this manual.
The chart also lists calibration values according to altitude. These values are only
approximate because they are derived from the average pressure at the given altitudes,
and do not take pressure variations into account. The typical error resulting from
calibration to altitude alone will be ±4% of your reading. Use altitude values only when
you cannot determine the true barometric pressure.

Calibration Section 3
YSI, Incorporated Model 52 6
3.3 CALIBRATION IN AIR
Three separate calibration techniques are discussed here: calibration in air, calibration in
air-saturated water, and calibration by Winkler titration. Choose the one technique which
best fits your application. Calibration in air is the simplest and most accurate method of
calibration.
To calibrate in air:
1. Place a prepared probe in air at 100% relative humidity. To achieve this, BOD probes
can be placed in a BOD bottle with approximately 1” of water. Field probes can be placed
in the plastic calibration bottle with a moistened sponge, or calibrated with the 5075A
Calibration Chamber (see probe instructions Appendix A).
2. Switch to CALIBRATE. The display will read:
Select percent calibration by pressing CONFIRM. A display similar to the one below
will be shown.
3. Using !and ", adjust the number to the calibration value determined from the
altitude or pressure chart on the back of the Model 52. SKIP sets the value to 100.0%;
and shows the following display:
you may wish to do this to bring the setting quickly to a value near the one you want, then
continue with !and ". Pressing SKIP again sets the value to 0.0% (see Zeroing the
Probe). Pressing SKIP a third time brings it back to the last calibration value.
C a l i b r a t e
i n p e r c e n t ?
E n t e r c a l v a l u e
L a s t = 9 6. 4 %
E n t e r c a l v a l u e
S a t . = 1 0 0 %