YSI 52 User Manual
YSI Model 52
Dissolved Oxygen Meter
Operations
Manual
CONTENTS
SECTION 1 INTRODUCTION................................................................................................................. 1
1.1 PRINCIPLES
1.2 DISPLAY
1.3 FUNCTION
1.4 POWER
OF OPERATION...................................................................................................... 1
AND FUNCTION KEYS............................................................................................... 2
SWITCH ..................................................................................................................... 2
ON SELF-TEST................................................................................................................ 2
SECTION 2 PREPARING THE METER ............................................................................................... 3
SECTION 3 CALIBRATION ................................................................................................................... 5
PERCENT AND MG/L.................................................................................................................... 5
3.1
3.2 DETERMINING
3.3 CALIBRATION
3.4 CALIBRATION
3.5 CALIBRATION
3.6 ZERO
CALIBRATION ................................................................................................................... 8
3.7 RESETTING
CALIBRATION VALUE....................................................................................5
IN AIR.................................................................................................................. 6
IN AIR-SATURATED WATER.......................................................................... 7
BY WINKLER TITRATION............................................................................... 7
THE DEFAULT ZERO CALIBRATION ............................................................... 10
SECTION 4 SALINITY........................................................................................................................... 11
SECTION 5 OPERATION...................................................................................................................... 13
5.1 TEMPERATURE
5.2 DISSOLVED
5.3 MEASURING
5.4 RECORDING
5.5 REVIEWING
5.6 PRINTING
5.7 SENDING
5.8 ERASING
MEASUREMENTS ......................................................................................... 13
OXYGEN MEASUREMENTS .............................................................................. 13
OXYGEN IN FLUIDS OTHER THAN WATER.................................................. 13
TO INTERNAL MEMORY................................................................................... 14
RECORDED LIVE DATA..................................................................................... 15
DATA FROM MEMORY .......................................................................................... 16
RECORDED DATA TO A PERSONAL COMPUTER .............................................. 16
THE MODEL 52 MEMORY ....................................................................................... 17
SECTION 6 SYSTEM SETUP................................................................................................................18
6.1 SETTING
6.2 SETTING
6.3 SETTING
6.4 LAST
6.5 CONTRAST
THE TIME AND DATE............................................................................................... 18
UP AUTOSTABLE...................................................................................................... 18
COMMUNICATION PARAMETERS ........................................................................ 20
DIGIT SUPPRESSION....................................................................................................... 21
ADJUSTMENT........................................................................................................ 21
SECTION 7 PERSONAL COMPUTER INTERFACE........................................................................ 23
7.1 WRITING
YOUR OWN APPLICATIONS SOFTWARE ............................................................ 23
SECTION 8 MAINTENANCE AND TROUBLESHOOTING............................................................ 25
8.1 BATTERIES.................................................................................................................................. 25
8.2 POWER
ON SELF-TESTING AND ERROR DISPLAY MESSAGES ........................................ 25
SECTION 9 DISCUSSION OF MEASUREMENT ERRORS............................................................. 27
9.1 TYPE
9.2 TYPE
9.3 TYPE
9.4 ERROR
1 ERRORS – INSTRUMENT COMPONENTS.................................................................. 27
2 ERRORS – PROBE ACCURACY ................................................................................... 27
3 ERRORS - CALIBRATION............................................................................................. 28
CALCULATION EXAMPLE.......................................................................................... 28
SECTION 10 WARRANTY AND REPAIR ...................................................................................... 31
i
AUTHORIZED
CLEANING
PACKING
U.S. SERVICE CENTERS............................................................................................ 32
INSTRUCTIONS............................................................................................................... 34
INSTRUCTIONS.................................................................................................................. 34
APPENDIX A GENERAL SPECIFICATIONS................................................................................... 37
APPENDIX B REQUIRED NOTICE ................................................................................................... 39
APPENDIX C OXYGEN SOLUBILITY.............................................................................................. 41
APPENDIX D CALIBRATION TABLES............................................................................................ 43
ii
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 semi
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.
YSI, Incorporated Model 52 1
Introduction Section 1
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,¿ ,À , and CONFIRM. ¿ andÀ 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
O
-TEMP, the instrument is measuring dissolved oxygen and temperature. To begin
2
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 2
SECTION 2 PREPARING THE METER
To prepare the meter for use, connect a prepared probe to the meter. Set the function
switch to O
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. If you have a problem you cannot resolve, call YSI Technical Support,
(937) 767-7241 or (800) 765-4974.
-TEMP. Observe temperature and oxygen readings for stability, or set up
2
6.33 mg/L 19.9C
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.
88.1 % 11: 52
YSI, Incorporated Model 52 3
Preparing the Meter Section 2
YSI, Incorporated Model 52 4
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 D 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.
YSI, Incorporated Model 52 5
Calibration Section 3
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.
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 À, 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 À. 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.
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 %
C a l i b r a t e
i n p e r c e n t ?
YSI, Incorporated Model 52 6
Calibration Section 3
4. When you have adjusted the reading to the desired value (let’s say you chose 98.0%),
press CONFIRM. The instrument will display the legend “Please wait” for a few seconds.
Then it will display:
You are now ready to measure dissolved oxygen.
C a l i b r a t e d t o
9 8. 0 %
3.4 CALIBRATION IN AIR-SATURATED WATER
A second alternative for calibration is to calibrate in air-saturated water. This procedure
is the same as the procedure for calibration in air except that the calibration medium is
saturated water rather than saturated air.
To calibrate in air-saturated water:
1. Air-saturate a volume of water (300 to 500 mL) by aerating for at least 15 minutes at a
relatively constant temperature.
2. Place the probe in the sample and provide adequate stirring (at least 1 foot per second).
Switch to O
take 5 minutes for the temperature to come to equilibrium. If you have just turned the
instrument on, allow 15 minutes for the system to equilibrate.
3. Switch to CALIBRATE, select percent calibration, then adjust the number in the
display to the correct value based on current barometric pressure or altitude and press
CONFIRM.
-TEMP and observe temperature and oxygen readings for stability. It may
2
3.5 CALIBRATION BY WINKLER TITRATION
A third alternative for calibration is to calibrate to a known oxygen value determined by a
Winkler titration.
To calibrate using a Winkler-titrated sample:
1. Determine the dissolved oxygen value of a sample by Winkler titration.
2. Place the probe in the sample and provide adequate stirring (at least 1 foot per second).
Switch to O
-TEMP and observe temperature and oxygen readings for stability.
2
YSI, Incorporated Model 52 7
Calibration Section 3
3. Switch to CALIBRATE. The display will read:
Press SKIP. The display will read:
Press CONFIRM to select mg/L calibration. A display similar to the one below will be
shown.
C a l i b r a t e
i n p e r c e n t ?
C a l i b r a t e
i n m g / L ?
4. Use ¿ and À to set the calibration value determined by Winkler titration. You may be
able to set the value more quickly by using the SKIP key to bring the value near the one
you want, then continuing with ¿ and À. Pressing SKIP once sets the value to the
saturation value of oxygen in water at the probe temperature. A display similar to the one
below will be shown.
Pressing SKIP again sets the value to 0.00 mg/L. (See Zero Calibration, below.) Pressing
SKIP a third time brings it back to the last calibration value.
5. When the correct value is set, press CONFIRM. The display will show the legend
“Please wait” for a few seconds, and then display “Calibrated to...” To take dissolved
oxygen readings in mg/L, switch to O
Note: Since there is no way to determine percent air saturation after a calibration in
mg/L, the % reading will be disabled.
E n t e r c a l v a l u e
L a s t = 8 . 1 5 m g / L
E n t e r c a l v a l u e
S a t . = 8 . 5 8 m g / L
-TEMP.
2
3.6 ZERO CALIBRATION
In rare applications, the accuracy of the calibration can be improved by performing a zero
calibration along with one of the procedures discussed previously.
All oxygen probes have a small background current, even in the absence of oxygen.
Model 52 compensation is based on the average background current of YSI 5700 and
YSI, Incorporated Model 52 8
Calibration Section 3
5900 Series probes. This is the default zero value. Although using this average will result
in errors with probes whose background current differs from the average.
Note: Errors will be insignificant in most applications. See Discussion of Measurement
Errors.
For highest accuracy measurements, a zero calibration should be performed to
compensate for the specific background current of the probe in use.
To calibrate to a true zero, place the probe in a zero oxygen environment and adjust the
calibration value to zero.
A standard method for creating such an environment is to dissolve in water (preferably
the water should come from the sample to be measured) excess sodium sulfite (Na
and a trace of cobalt chloride (CoCl
). These chemicals will remove all oxygen from the
2
2SO3
),
sample (See Standard Methods for the Examination of Water & Wastewater, 17th
edition, 1989, page 4-161.) Alternatively, you may place the probe in 100% nitrogen gas.
Place the probe in the zero oxygen sample, switch to O
-TEMP and allow at least 20
2
minutes for the probe to come to equilibrium.
Switch to CALIBRATE. The display will show:
C a l i b r a t e
i n p e r c e n t ?
Press CONFIRM to select percent calibration. A display similar to the one below will be
shown:
E n t e r c a l v a l u e
L a s t = 9 2 . 5 %
Press SKIP twice to set the calibration value to 0.0%. The following display will be
shown.
E n t e r c a l v a l u e
Z e r o = 0. 0 %
Press CONFIRM to calibrate to zero. The display will ask you to wait, then show
"Calibrated to 0.0 %." After zeroing, rinse the probe thoroughly to remove any residual
trace of chemicals.
The Model 52 is calibrated at two points: the calibration value you select, and its default
zero.
YSI, Incorporated Model 52 9
Calibration Section 3
Note: When you change the zero calibration point, you offset the other value, so that
after zeroing the probe for zero oxygen, you must recalibrate in an oxygen environment.
If you try to take readings without recalibrating, the display will provide this warning:
You may also select mg/L calibration and then zero-calibrate and the result will be the
same.
8 . 7 4 m g / L 2 5 . 6 C
R e c a l i b r a t e
3.7 RESETTING THE DEFAULT ZERO CALIBRATION
To reset the zero calibration to its default value, turn the instrument off and then hold
down SKIP and ¿ while turning the instrument back on again. The display below will
show briefly, then the POST operation and display will resume.
This procedure resets the meter to its original state. You must reset the time, date,
salinity, and the RS232 parameters after restoring the default zero. As with the zero
calibration, you must also recalibrate after restoring the default zero.
S y s t e m r e s e t t o
d e f a u l t v a l u e s
YSI, Incorporated Model 52 10
SECTION 4 SALINITY
Salt reduces the ability of water to hold oxygen in solution. Enter the salinity of the
sample you are measuring, and the meter will automatically compensate for the effect of
salinity on dissolved oxygen. The default salinity setting is 0.0 ppt. You can enter any
salinity setting between 0.0 and 40.0 ppt. To do this, turn the function switch to
SALINITY. A display similar to the one below will show:
Use ¿ and À to adjust the salinity setting. You might find it quicker to press SKIP first,
which will set the value to 35.0 ppt. The following display will be shown:
Pressing SKIP again will set the value to 0.0 ppt for fresh water measurements. The
following display will be shown:
E n t e r s a l i n i t y
S e t t i n g = 0 . 0
E n t e r s a l i n i t y
S e a w a t e r = 3 5 . 0
E n t e r salinity
Fresh = 0. 0
Pressing SKIP once more will bring the setting to its original value. Once you have set
the salinity correctly, press CONFIRM. The instrument will ask you to wait, then show
you the new salinity setting.
If you have calibrated using the air saturation method, there is no need to recalibrate after
changing the salinity setting. If you have calibrated in mg/L, then you must recalibrate
after setting the salinity.
After calibrating in air or in air-saturated water, you may change the meter's salinity
setting without recalibrating. You may, for instance, calibrate only once and then proceed
to measure oxygen in a variety of samples at different salinity by simply setting the
proper salinity before making each measurement.
YSI, Incorporated Model 52 11
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