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

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NEVER EXTEND THE CABLE
WITH CHEAP JUMPER WIRES!
DO NOT CUT THE PROBE CABLE
WITHOUT REFERING TO THIS DOCUMENT!
5Copyright © Atlas Scientific LLC

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DO NOT MAKE YOUR OWN
UNSHIELDED CABLES!
ONLY USE SHIELDED CABLES.
REFER TO THIS DOCUMENT!
6Copyright © 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

Range .001 − 14.000
1 reading per sec
Response time
+/– 0.002
Accuracy
Any type & brand
Supported probes
1, 2, 3 pointCalibration
UART & I2CData protocol
99 (0x63)
Default I2C address
3.3V − 5V
Operating voltage
ASCII
Data format
YesTemp compensation
Reads pH
.001
Resolution
EZO-pH™
Embedded pH Circuit
V 5.1
Revised 10/23/18
This is an evolving document, check back for updates.
Written by Jordan Press
Designed by Noah Press
PATENT PROTECTED

This is sensitive electronic equipment. Get this device working in
a solderless breadboard first. Once this device has been soldered
it is no longer covered by our warranty.
This device has been designed to be soldered and can be soldered
at any time. Once that decision has been made, Atlas Scientific no
longer assumes responsibility for the device’s continued operation.
The embedded systems engineer is now the responsible party.
Get this device working in a
solderless breadboard first!
Do not embed this device without
testing it in a solderless breadboard!
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r 0.1

UART I2C
Circuit dimensions
Power consumption
Absolute max ratings
EZO
TM circuit identification
Operating principle
Calibration theory
Power and data isolation
Correct wiring
Available data protocols
Circuit footprint
Datasheet change log
Warranty
UART mode
Default state
Receiving data from device
Sending commands to device
LED color definition
UART quick command page
LED control
Find
Continuous reading mode
Single reading mode
Calibration
Export/import calibration
Slope
Temperature compensation
Naming device
Device information
Response codes
Reading device status
Sleep mode/low power
Change baud rate
Protocol lock
Factory reset
Change to I2C mode
Manual switching to I2C
I2C mode
Sending commands
Requesting data
Response codes
LED color definition
I2C quick command page
LED control
Find
Taking reading
Calibration
Export/import calibration
Slope
Temperature compensation
Device information
Reading device status
Sleep mode/low power
Protocol lock
I2C address change
Factory reset
Change to UART mode
Manual switching to UART
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Table of contents
3Copyright © Atlas Scientific LLC

Power consumption
1.16 mA
0.995 mA
LED MAX STANDBY SLEEP
ON 18.3 mA 16 mA
13.8 mA 13.8 mA
14.5 mA 13.9 mA
13.3 mA 13.3 mA
ON
OFF
OFF
5V
3.3V
Absolute max ratings
MIN MAXTYPParameter
-65 °C 125 °C
85 °C25 °C-40 °C
Storage temperature
(EZO™ pH)
VCC
Operational temperature
(EZO™ pH)
5V 5.5V3.3V
EZO
TM circuit dimensions
13.97mm
(0.55”)
20.16mm
(0.79”)
8.38mm
(0.32”)
10.8mm
(0.4”)
5.8mm
(0.22”) 1mm Ø
r 0.1
4Copyright © Atlas Scientific LLC

EZO
TM circuit identification
Viewing correct datasheet Viewing incorrect datasheet
EZO™ pH circuit Legacy pH circuit
Click here to view legacy datasheet
r 0.1
5.0
5.0
5Copyright © 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 > 7Neutral: pH = 7Acid: pH < 7
Junction
Reference wire
Silver chloride
Silver wire
KCL reference solution
6Copyright © Atlas Scientific LLC

Calibration theory
The Atlas Scientific EZO™class pH circuit has a flexible calibration protocol, allowing for
single point, two point, or three point calibration.
The EZO™pH circuits default temperature compensation is set to 25° C. If the temperature
of the calibration solution is +/- 2° C from 25° C, consider setting the temperature
compensation first. Temperature changes of < 2° C are insignificant.
The first calibration point must be the Midpoint (pH 7)
Single point calibration
1. Remove soaker bottle and rinse off pH probe.
2. Pour a small amount of the calibration solution into a cup.
3. Let the probe sit in calibration solution until readings stabilize (1 – 2 minutes).
4. Calibrate the midpoint value using the command "Cal,mid,n".
Where "n" is any floating point value that represents the calibration midpoint.
5. Do not pour the calibration solution back into the bottle.
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1 2 3 1:00 −2:00 4 5
“Cal,mid,n”
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1 2 3 1:00 −2:00 4 5
“Cal,low,n”
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1 2 3 1:00 −2:00 4 5
“Cal,high,n”
Lowpoint HighpointMidpoint
14
"cal,low,n" "cal,mid,n" "cal,high,n"
The most important part of calibration is watching the readings during the calibration
process. It's easiest to calibrate the device in its default state (UART mode, continuous
readings). Switching the device to I2C mode after calibration will not affect the stored
calibration. If the device must be calibrated in I2C mode be sure to request readings
continuously so you can see the output from the probe.
7Copyright © Atlas Scientific LLC

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“Cal,mid,n”
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“Cal,low,n”
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“Cal,high,n”
Two point calibration
1. Rinse off pH probe.
2. Pour a small amount of the calibration solution into a cup
3. Let the probe sit in calibration solution until readings stabilize (1 – 2 minutes).
4. Calibrate the lowpoint value using the command "Cal,low,n".
Where "n" is any floating point value that represents the calibration lowpoint.
5. Do not pour the calibration solution back into the bottle.
1. Rinse off pH probe.
2. Pour a small amount of the calibration solution into a cup
3. Let the probe sit in calibration solution until readings stabilize (1 – 2 minutes).
4. Calibrate the highpoint value using the command "Cal,high,n".
Where "n" is any floating point value that represents the calibration highpoint.
5. Do not pour the calibration solution back into the bottle.
Three point calibration
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“Cal,high,n”
Issuing the cal,mid command after the EZO™pH circuit
has been calibrated will clear the other calibration points.
Full calibration will have to be redone.
8Copyright © Atlas Scientific LLC

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Correct
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Incorrect
Power and data isolation
The Atlas Scientific EZO™pH circuit is a very sensitive device. This sensitivity is what gives
the pH circuit its accuracy. This also means that the pH circuit is capable of reading
micro-voltages that are bleeding into the water from unnatural sources such as pumps,
solenoid valves or other probes/sensors.
When electrical noise is interfering with the pH readings it is common to see rapidly
fluctuating readings or readings that are consistently off. To verify that electrical noise is
causing inaccurate readings, place the pH probe in a cup of water by itself. The readings
should stabilize quickly, confirming that electrical noise was the issue.
When reading pH and Conductivity or Dissolved Oxygen together, it is
strongly recommended that the EZO™ pH circuit is electrically isolated from
the EZO™Conductivity or Dissolved Oxygen circuit.
Without isolation, Conductivity and Dissolved Oxygen
readings will effect pH accuracy.
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Correct
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Incorrect
Basic EZO
TM
Inline Voltage Isolator
r 0.1
9Copyright © Atlas Scientific LLC

This schematic shows exactly how we isolate data and power using the ADM3260
and a few passive components. The ADM3260 can output isolated power up to 150 mW
and incorporates two bidirectional data channels.
This technology works by using tiny transformers to induce the voltage across an air gap.
PCB layout requires special attention for EMI/EMC and RF Control, having proper ground
planes and keeping the capacitors as close to the chip as possible are crucial for proper
performance. The two data channels have a 4.7kΩpull up resistor on both the isolated
and non-isolated lines (R1, R2, R3, and R4) The output voltage is set using a voltage
divider (R5, R6, and R,7) this produces a voltage of 3.9V regardless of your input voltage.
Isolated ground is different from non-isolated ground, these two lines should not
be connected together.
r 0.2
C4
10uF
C1
0.1uf
VDDP
ADM3260
HDR_BTM
ISO-VCC
ISO-VCC
ISO-VCC
ISO-VCC
ISO-VCC
R5 R7
R4
R3
1.5K
R6
1.5K
C3
C2
C6
C5
10uF
10uF
0.1uF
0.1uF
1.5K
4.7K
4.7K
VDDISO
VISO
VSEL
NCNC
SCL1
SDA1
SCL2
SDA2
VIN
GNDP
GNDISO
GNDISO
GNDISO
GNDISO
GNDP
GNDP
GNDP
PDIS
VCC
VCC
VCC
VCC
VCC
VCC
RX/SCL
TX/SDA
NC
GND
ISO-GND
ISO-GND
GND
R2 R14.7K 4.7K
R5
1M
HDR_TOP
VCC
RX/SCL
TX/SDA
EN
GND
Non-isolated
N-FET
VCC = 3.0v − 5.5v
Isolated
D
G
S
GND
VCC
R8
1M
10 Copyright © Atlas Scientific LLC