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Welcome to OHAUS (www.ohaus.com)!
After more than a century of perfecting the art of measurement through our durable weighing products, OHAUS
precision is now available in a line of portable electrochemistry products that provides accurate measurement of DO,
pH, ORP, conductivity, TDS and salinity.
ST series pen meters are the economical option when you are simply looking for meters that are easy to use and
provide accurate measurements.
The pen meters should not be used by Children of age 12 or younger.
This product conforms to the EMC Directive 2004/108/EC. The Declaration of Conformity is available online at
europe.ohaus.com/europe/en/home/support/compliance.aspx.
Thank you for choosing OHAUS waterproof pen Dissolved Oxygen meter ST20D. Please read the manual completely before
use.
First Usage
Take o the membrane part by turning it, ll the electrolyte, then put on the membrane. Warm up the DO pen meter by turning it on. The meter will
turn off automatically after 10 minutes.
Calibration and measurement
After warm up, turn on the meter. Put the ST20D in the air and press button "Cal";
The meter display will show a blinking "100", the meter is now calibrating 100% DO value. After 3 to 5 minutes when the blinking has stopped,
press button "Hold/Enter" to nish 100% DO calibration.
There are now two options:
1. Press button "Hold/Enter" to nish 1 point calibration and exit to measurement interface.
Note: Ohaus suggest to only do 1 point (100%) calibration for ST20D. There is no need to perform 2 point (0%) calibration
unless the sample DO value is too low (e.g. <1 mg/L).
2. Put the ST20D into the Zero-Oxygen solution. Press button "Cal" to do the 0% point calibration, LCD will show a blinking "0".
After about 3 minutes, when the blinking has stopped, press button "Hold/Enter" to nish 0% calibration.
Zero-Oxygen solution is saturated Na SO (CAS NO 7757-83-7) solution. Ohaus provides DO zero-oxygen chemical (30059257).
After calibration, rinse the pen DO tip. The sample can now be measured.
Maintenance and Storage
After usage, take o the membrane, rinse the electrode and membrane, dry them and put the membrane back on. Store the meter.
Harsh samples, such as sticky, dirty or oily liquids, may shorten the pen meters life time, .
The electrode is replaceable.
ST 20D Pen DO Meter
Instruction Manual
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