Extech Instruments SDL150 User manual

User's Guide
Dissolved Oxygen (DO) Meter
SD Card real-time Datalogger
Model SDL150

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Introduction
Congratulations on your purchase of the Extech SDL150 Dissolved Oxygen Meter, an SD Logger
Series meter. This meter displays and stores Dissolved Oxygen readings in the 0 to 20.0mg/L
range, Oxygen in air from 0 to 100%, and Temperature from 0 to 50
o
C (32 to 122
o
F). The SDL150
uses a polarographic oxygen probe that also measures temperature. %Salt and Altitude
compensation can be fine tuned by the user in the Setup mode. Logged data readings are stored on
an SD card for transfer to a PC. In addition, an RS232 port allows data streaming to a PC. This
meter is shipped fully tested and calibrated and, with proper use, will provide years of reliable
service.
Safety
International Safety Symbols
This symbol, adjacent to another symbol or terminal, indicates the user must refer to the
manual for further information.
Meter Description
1. Oxygen Probe Input Plug
2. Dissolved Oxygen or Oxygen in Air reading
3. Temperature reading
4. Power ON-OFF key
5. SET and Clock key
6. Up arrow ▲/ CAL key
7. Down arrow ▼/ Function key
8. ENTER and LOG key
9. SD card slot
10. Dissolved Oxygen/Temperature Probe
11. HOLD and Backlight key
12. MAX-MIN key
13. PC interface jack
14. Reset button
15. Power Adaptor jack
Notes:
Items 13, 14, and 15 are located behind the snap-off compartment cover on meter’s right side.
Battery compartment, tilt stand, and tripod mount are located on the rearof the instrument

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Probe Description
1. Probe to meter input plug
2. Probe body handle
3. Temperature Sensor
4. Probe head
5. Protective cap
Getting Started
Accessories
•The SDL150 includes batteries, SD card, probe (with spare probe head and diaphragm),
electrolyte, and carry case. If items are missing please contact the distributor through which this
product was purchased
•Optional AC adaptor and universal AC adaptors (UK, EU, US), as well as replacement probes,
membranes, and electrolyte are available through Extech distributors
Power ON-OFF
•Press and hold the power button for at least 1.5 seconds to power ON the meter.
•Press and hold the power button for 1.5 seconds to power OFF the meter.
•This meter is powered by six (6) 1.5VDC ‘AA’ batteries or by optional AC adaptor. If the meter
will not switch ON please check that fresh batteries are installed in the rear battery compartment
or, in the case of the AC adaptor, check that the adaptor is connected correctly to the meter and
to an AC source.
Measurements
Connect the Oxygen Probe
The supplied probe connects to the keyed input jack (DIN style) at the top of the meter.
Measurement Ranges
Dissolved Oxygen measurements are displayed in the range of 0 to 20mg/L in the upper, larger digit
display area of the meter’s LCD. Measurements outside of this range will yield dashes (- - -) on the
meter’s LCD. Oxygen in Air measurements (O2) are displayed in the range of 0 to 100%.
Temperature measurements are displayed in the range of 0 to 50
o
C (32 to 122
o
F) on the lower LCD
line in smaller sized digits.
Calibration Considerations
For best accuracy, calibrate the meter with the probe before each use. The calibration should at be
performed before first use and after long periods of non-use. The calibration procedure is provided
in a later section of this user guide.

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Taking Dissolved Oxygen Measurements
1. Immerse the DO probe into the solution under test to a depth of at least 10cm. The depth
specification is important since the temperature measurement of the solution and the automatic
temperature compensation circuitry rely on the probe depth to operate correctly.
2. Allow the test to stabilize for several minutes to achieve thermal equilibrium between the probe
and measurement sample.
3. To successfully measure DO the velocity of the solution striking the probe must be at least 0.2-
0.3m/s (meters per second); if not, simply agitate the solution with the probe while waiting for
thermal equilibrium to be achieved.
4. In laboratory environments use of a magnetic agitator to ensure proper velocity is
recommended. In this way, errors due to the diffusion of the oxygen present in the surrounding
air are minimized.
5. The Dissolved Oxygen measurements are displayed on the upper, larger digit display area of
the meter’s LCD. Measurements outside of the specified range will yield dashes (- - -).
Temperature measurements are displayed in the range of 0 to 50
o
C (32 to 122
o
F) on the lower
LCD line in smaller sized digits.
6. %SALT, Altitude (height) compensation, temperature units of measure, and other parameters,
can be modified in the SETUP mode (refer to the SETUP mode section later in this guide).
Taking Oxygen in Air Measurements
1. The probe measures Oxygen in the air surrounding the probe (in percent).
2. The meter defaults to the DO measurement mode. Therefore, press and hold the FUNCTION
button for 1.5 seconds to switch to the %O2 mode (oxygen in air). The displayed unit of
measure will switch from mg/L to 02. To return to the DO measurement mode simply press and
hold the FUNCTION button again for 1.5 seconds.
3. The Oxygen in Air measurements are displayed on the upper, larger digit display area of the
meter’s LCD. Measurements outside of the specified range will yield dashes (- - -). Temperature
measurements are displayed in the range of 0 to 50
o
C (32 to 122
o
F) on the lower LCD line in
smaller sized digits.

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Calibration
20.9% Oxygen in Air Calibration
1. Connect the DO probe to the input jack at the top of the meter
2. Power the meter by pressing and holding the power button for 1.5 seconds
3. Press and hold the FUNCTION button for 1.5 seconds to switch from mg/L mode to O2 mode
4. Allow the probe to stabilize for at least 5 minutes in a large well ventilated environment.
5. Press and hold the CAL button for 1.5 seconds. The CAL icon will appear
6. Momentarily press the ENTER button while the CAL icon is displayed. The display will indicate a
countdown from 30 to zero. Note that if the ENTER button is not pressed while the CAL icon is
being displayed, the calibration procedure must be attempted again
7. When the countdown finishes the calibration is complete
8. If the calibration is unstable, check the electrolyte level and/or replace the probe head (includes
diaphragm)
Zero Calibration
The 0% calibration is available for high accuracy measurements at low O
2
levels. The calibration
requires a Zero Oxygen Solution which can be purchased from most laboratory supply distributors.
This calibration is not required for typical O
2
measurements.
1. Power the meter on and set it to DO mode (you should see mg/L in the top right of display).
2. Immerse the probe in 4” of zero oxygen solution; agitate or slowly stir the probe in the solution
to remove any air bubbles and allow the reading to stabilize.
3. Once the reading has stabilized, press and hold the UP and DOWN arrow buttons until CAL 0
appears in the lower portion of the display.
4. Release the UP and DOWN arrow buttons; calibration is complete.

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Probe Maintenance
First time use
Before first use, ensure that the probe is filled with the supplied electrolyte solution (refer to the
electrolyte filling instructions later in this guide)
Subsequent uses
1. Ensure proper electrolyte level in probe
2. Calibrate the probe with the meter before each use
3. Replace the probe head and diaphragm if the diaphragm appears soiled (re-calibrate after
replacing diaphragm)
Diaphragm considerations
The main oxygen probe component is the thin Teflon diaphragm housed in the tip of the supplied
probe. The diaphragm is made permeable by the oxygen molecules but not by the considerably
larger molecules contained in the electrolyte. Due to this characteristic, the oxygen may diffuse
throughout the electrolyte solution contained in the probe and its concentration is quantified by the
meter’s measurement circuitry.
Refilling the Probe’s Electrolyte
Refer to the illustrated instructions below.
1. Unscrew the probe head
2. Pour out the old electrolyte from the probe head container
3. Fill the probe head container with the fresh electrolyte
4. Replace the probe head onto the probe body
5. When not in use the probe head should be kept in the protective cover

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Display Backlight
To turn the display backlight ON or OFF, press and hold the backlight button for at least 1.5
seconds.
Data Hold
To freeze a displayed reading on the LCD, momentarily press the HOLD button (the HOLD display
icon will appear). To release the held reading, press the HOLD button again.
Max-Min Reading Record and Recall
For a given measurement session, this meter can record the highest (MAX) and the lowest (MIN)
readings for later recall.
1. Press the MAX-MIN button momentarily to access this mode of operation (REC icon appears)
the meter is now recording the MAX and MIN readings.
2. Press the MAX-MIN button again to view the current MAX readings (MAX icon appears). The
readings on the display are now the highest readings encountered since the REC icon was
switched on (when the MAX-MIN button was first pressed).
3. Press the MAX-MIN button again to view the current MIN readings (MIN icon appears). The
readings on the display are now the lowest readings encountered since the REC icon was
switched on (when the MAX-MIN button was first pressed).
4. To exit the MAX-MIN mode, press and hold the MAX-MIN button for at least 1.5 seconds The
meter will beep, the REC-MAX-MIN icons will switch off, the MAX-MIN memory will clear, and
the meter will return to the normal operating mode.

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Setup Mode
Basic settings at a glance
To view the current configuration of the meter with regard to time, date, and datalogging sampling
rate press the SET button momentarily. The meter will now display the configuration in quick
succession. Repeat as necessary to observe all the information.
Accessing the Setup mode
1. Press and hold the SET button for at least 1.5 seconds to access the Setup menu.
2. Press the SET button momentarily to step through the available parameters. The parameter
type is shown on the bottom of the LCD and the current selection for that type is shown above it.
3. When a parameter is displayed that is to be changed, use the arrow keys to change the setting.
Press the ENTER button to confirm a change.
4. Press and hold the SET button for at least 1.5 seconds to exit the Setup mode. Note that the
meter automatically switches out of the Setup mode if no key is pressed within 7 seconds.
5. The available Setup parameters are listed below. Additional detailed information is provided
below this list:
dAtE Set the clock (Year/Month/Date; Hours/Minutes/Seconds)
SP-t Set the datalogger sampling rate (Hours/Minutes/Seconds)
PoFF Automatic power-off (Enable/disable the auto-power off function)
bEEP Set the beeper sound ON/OFF
dEC Set the numerical format; USA (decimal: 20.00) or European (comma: 20,00)
Sd F Format the SD memory card
t-CF Select the desired unit of measure for temperature C or F
SALT %Salt compensation (0 to 50%)
HEIGHT Altitude compensation (in meters) up to 8900 meters
HEIGHT-F Altitude compensation (in feet) up to 29300 feet
Setting the Clock Time
1. Access the dAtE parameter.
2. Use the arrow keys to change a value
3. Use the ENTER button to step through the selections
4. Press and hold the SET button for at least 1.5 seconds to exit to the normal operation mode (or
simply wait 7 seconds for the meter to automatically switch to the normal operating mode).
5. The clock will keep accurate time even when the meter is switched off. However, if the battery
expires the clock will have to be reset after fresh batteries are installed.
Setting the Datalogger Sampling Time (Rate)
1. Access the SP-t parameter.
2. The sampling rate can be set from ‘0’ seconds (manual log mode) up to 8 hours, 59 minutes,
and 59 seconds.
3. Use the ENTER button to move through the Hours, Minutes, and Seconds digit groups and use
the arrow keys to change the digit values.
4. PresstheENTERbuttontoconfirm theentry.
5. Press and hold the SET button for at least 1.5 seconds to exit to the normal operation mode (or
simply wait 7 seconds for the meter to automatically switch to the normal operating mode).

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Enabling/Disabling the Auto Power OFF Feature
1. Access the PoFF parameter.
2. Use the arrow buttons to select ON (enable) or OFF (disable). With the Auto Power OFF
feature enabled, the meter will automatically switch OFF after 5 minutes of inactivity.
3. Press ENTER to confirm setting.
4. Press and hold the SET button for at least 1.5 seconds to exit to the normal operation mode (or
simply wait 7 seconds for the meter to automatically switch to the normal operating mode).
Set the Beeper Sound ON or OFF
1. Access the bEEP parameter.
2. Use the arrow buttons to select ON (enable) or OFF (disable).
3. Press ENTER to confirm setting.
4. Press and hold the SET button for at least 1.5 seconds to exit to the normal operation mode (or
simply wait 7 seconds for the meter to automatically switch to the normal operating mode).
Numerical Format (comma or decimal)
European and USA numerical formats differ. The meter defaults to USA mode where a decimal
point is used to separate units from tenths, i.e. 20.00; The European format uses a comma, i.e.
20,00 to separate units from tenths. To change this setting:
1. Access the dEC parameter.
2. Use the arrow buttons to select USA or EUro.
3. Press ENTER to confirm setting.
4. Press and hold the SET button for at least 1.5 seconds to exit to the normal operation mode (or
simply wait 7 seconds for the meter to automatically switch to the normal operating mode).
SD Card FORMATTING
1. Access the Sd F parameter.
2. Use the arrow buttons to select YES to format the card (select NO to abort). Note that all data
on the card will be lost if formatting is attempted.
3. Press ENTER to confirm selection.
4. Press ENTER again to re-confirm.
5. The meter will automatically return to the normal operating mode when formatting is complete.
If not, press and hold the SET button for at least 1.5 seconds to exit to the normal operation
mode.
Set the Temperature Units of Measure (°C or °F)
1. Access the t-CF parameter.
2. Use the arrow keys to select °C or °F.
3. Press ENTER to confirm setting.
4. Press and hold the SET key for at least 1.5 seconds to exit to the normal operation mode (or
simply wait 7 seconds for the meter to automatically switch to the normal operating mode).
Set the %SALT Compensation
1. Access the SALT parameter.
2. Use the arrow keys to select the %SALT compensation (0 to 50%)
3. Press ENTER to confirm setting.
4. Press and hold the SET key for at least 1.5 seconds to exit to the normal operation mode (or
simply wait 7 seconds for the meter to automatically switch to the normal operating mode).

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Set the Altitude Compensation (in meters) for DO measurements only
1. Access the Height parameter.
2. Use the arrow keys to select the altitude compensation (0 to 8900 meters in 100 meter steps)
3. Press ENTER to confirm setting.
4. Press and hold the SET key for at least 1.5 seconds to exit to the normal operation mode (or
simply wait 7 seconds for the meter to automatically switch to the normal operating mode).
Set the Altitude (F) Compensation (in feet) for DO measurements only
1. Access the Height-F parameter.
2. Use the arrow keys to select the altitude compensation (0 to 29,300 feet in 100 feet steps)
3. Press ENTER to confirm setting.
4. Press and hold the SET key for at least 1.5 seconds to exit to the normal operation mode (or
simply wait 7 seconds for the meter to automatically switch to the normal operating mode).
System Reset
If the meter’s keys become inoperable or if the display freezes the Reset button can be used to
reset the instrument.
1. Use a paper clip or similar item to momentarily press the reset button located on the lower right
side of the instrument under the snap-off compartment cover.
2. After pressing the Reset button, switch the instrument ON by pressing and holding the
POWER key for at least 1.5 seconds. If using the power adaptor unplug the adaptor and then
plug it back in again to power the meter.
Datalogging
Types of Data Recording
•Manual Datalogging: Manually log up to 99 readings onto an SD card via push-button press.
•Automatic Datalogging: Automatically log data onto an SD memory card where the number of
data points is virtually limited only by the card size. Readings are logged at a rate specified by
the user.
SD Card Information
•Insert an SD card (from 1G size up to 16G) into the SD card slot at the bottom of the meter. The
card must be inserted with the front of the card (label side) facing toward the rear of the meter.
•If the SD card is being used for the first time it is recommended that the card be formatted and
the logger’s clock set to allow for accurate date/time stamping during datalogging sessions.
Refer to the Setup Mode section for SD card formatting and time/date setting instructions.
•European and USA numerical formats differ. The data on the SD card can be formatted for
either format. The meter defaults to USA mode where a decimal point is used to separate units
from tenths, i.e. 20.00. The European format uses a comma, i.e. 20,00. To change this setting,
refer to the Setup Mode section.