Atlas Scientific EZO-pH User manual
pH Probe
Range 0 − 14
95% in 1s
Response time
100 PSI
Max pressure
1 meter
Cable length
No
Internal temperature sensor
~1 Year
Time before recalibration
~2.5 Years +
Life expectancy
N/A
Maintenance
Silver / silver chloride
Reads pH
+/- 0.0001
Resolution
1 − 99 °C
Temperature range °C
60m (197 ft)
Max depth
Revised 12/12/18
V 3.1
120mm
(4.7”)
150mm
(6”)
30mm
(1.18”)
12mm
(0.47”)
Ø 14.3mm
Cable Length
1m (3.2’)
Sensing area
15.55mm
(0.61”)
Ø 2.85mm
Max depth
Cable length
Weight
Speed of response
Isopotential point
Dimensions
BNC connector
Sterilization
Food Safe
Specifications
60m (197 ft)
1 meter
49 grams
95% in 1 second
pH 7.00 (0 mV)
12mm x 150mm (0.5" x 6")
Yes
Chemical only
Yes
• Standard lab use
• Field use
• Soil
• Low ionic and ultra-pure water
• High pH solutions (up to 14 pH)
• Samples containing heavy metals
• Hydroponics / aquaponics
• Beer, wine and other liquor
Typical Applications
This pH probe can be fully submerged
in fresh or salt water, up to the BNC
connector indefinitely.
Soaker bottle
~3.8 pH
2Copyright © Atlas Scientific LLC
Operating principle
A pH (potential of Hydrogen) probe measures the hydrogen ion activity in a liquid.
At the tip of a pH probe is a glass membrane. This glass membrane permits hydrogen
ions from the liquid being measured to defuse into the outer layer of the glass, while
larger ions remain in the solution. The difference in the concentration of hydrogen ions
(outside the probe vs. inside the probe) creates a VERY small current. This current
is proportional to the concentration of hydrogen ions in the liquid being measured.
Base: pH > 7
Neutral: pH = 7Acid: pH < 7
Junction
Reference wire
Silver chloride
Silver wire
KCL reference solution
3Copyright © Atlas Scientific LLC
A pH electrode is a passive device that detects a current generated from hydrogen ion
activity. This current (which can be positive or negative) is very weak and cannot be
detected with a multimeter, or an analog to digital converter. This weak electrical signal
can easily be disrupted and care should be taken to only use proper connectors and cables.
The current that is generated from the hydrogen ion activity is the reciprocal of that
activity and can be predicted using this equation:
Because a pH probe is a passive device it can pick up voltages that are transmitted
through the solution being measured. This will result in incorrect readings and will
slowly damage the pH probe over time. In this instance, proper isolation is required.
Where Ris the ideal gas constant.
Tis the temperature in Kelvin.
Fis the Faraday constant.
4Copyright © Atlas Scientific LLC
Extending the probe cable length
You can extend the cable to greater than 100 meters with no loss of signal. Atlas Scientific
has tested up to 300 meters without a problem, however you run the risk of turning your
pH probe into an antennae, picking up noise along the length of your cable.
If you want to extend your cable, we recommend that you use proper isolation, such as
the Basic EZO
TM Inline Voltage Isolator, or Tentacle Shield. Be sure to calibrate your
probe with the extended cable.
Extending a probe cable can be easily done with our BNC Extension Cable. Simply
connect the BNC end of the probe to the Extension cable, and you are all set.
If you need to water proof a BNC connection, we highly recommend using a product like
Coax-Seal to safely cover and prevent any water damage that may occur.
Water proof
7Copyright © Atlas Scientific LLC
During shipment the air bubble in the probes stem may move into the bulb area.
If bubbles are seen in the bulb area, hold the probe by its top cap and shake
downward as done with a clinical thermometer.
Helpful operating tips
1
2
Take out the probe by loosening the cap of the soaker bottle by turning it counter
clockwise, and pulling the probe out. Slide the O-ring and the cap off the probe.
pH probes must stay wet and cannot be allowed to dry out, this is why every pH
probe is shipped in a plastic soaker bottle containing pH probe storage solution. The
probe should remain in the bottle until it is used. If the probe is used infrequently, the
bottle and its solution should be saved and the probe stored inside.
Ready to use
Bubbles
8Copyright © Atlas Scientific LLC
Vigorously stir the probe in the sample, calibration solution, or rinse solution.
This action will bring solution to the probes surface quicker and improve the
speed of response.
3
Response time
Probe cleaning
Coating of the pH bulb can lead to erroneous readings including shortened span (slope).
The type of coating will determine the cleaning technique. Soft coatings can be removed
by vigorous stirring or by the use of a squirt bottle. Organic chemical, or hard coatings,
should be chemically removed. A light bleach solution or even a 5 – 10% hydrochloric acid
(HCl) soak for a few minutes, often removes many coatings. If cleaning does not restore
performance, reconditioning may be tried. Do not use a brush or abrasive materials
on the pH probe.
9Copyright © Atlas Scientific LLC
Probe reconditioning
How often do you need
to recalibrate a pH probe?
Because every use case is different, there is no set schedule for recalibration.
If you are using your probe in a fish tank, a hydroponic system or any environment that
has generally weak levels of acids and bases you will only need to recalibrate your probe
once per year for the first two years. After that every ~six months.
If you are using the pH probe in batch chemical manufacturing, industrial process,
or in a solution that is known to have strong acids and bases, then calibration should be
done monthly or in extreme cases after each batch.
When reconditioning your pH probe is required due to aging, we recommend you use
the Atlas Scientific pH probe reconditioning kit.
10 Copyright © Atlas Scientific LLC
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