Atlas Scientific EZO Complete-pH USB pH Meter User Guide
- June 9, 2024
- Atlas Scientific
Table of Contents
Atlas Scientific EZO Complete-pH USB pH Meter User Guide
The EZO Complete-pH™ has all the features of this benchtop meter
- Three decimal pH reading
- Temperature used for reading
- Calibration slope
- Extended range capability
- Immediate reading
- Timed readings
- Set device name
- Voltage usage
- Multi-point variable calibration
- Temperature compensation
Interference free
The EZO complete readings are unaffected by other sensors in the same water
Ingress protection – IP62
The EZO-pH Complete ™ is dust proof and resistant to splashing water.
Two areas of concern are the USB connector and the probe connector.
Ingress protection – IP62
An electrical short can occur if water enters the USB connector. A USB short
could permanently damage the EZO-Complete. A USB short is not covered under
warranty.
A connector short can occur if water enters the SMA connector. A connector short will cause the pH readings to pin to 0, 14, or the probe will respond slowly to changes in pH.
A connector short is reversible and will not damage the EZO-Complete. However,
frequent shorts will eventually damage the pH probe.
The SMA connector is part of your probe; Nothing should be in contact with this part.
Do not use this as a mounting point!
Setup
pH probe with SMA Connector
pH probe with BNC Connector
Micro pH probe with half-cell adapter
AtlasDesktop
Setup
Once you have installed the AtlasDesktop monitoring software, you can begin
monitoring and logging your readings
Calibration theory
The accuracy of your readings is directly related to the quality of your calibration. (Calibration is not difficult, and a little bit of care goes a long way)
Single, Two point, or Three point calibration accuracy
Confirm the pH probe is working correctly
A new Atlas Scientific pH probe, still in its soaker bottle will read a pH of ~3.4 – 3.8
If your pH probe gives a reading of zero, seven or 14 continuously and that reading cannot be changed n matter what solution the probe is in, your probe cannot be calibrated and may be damaged.
Contact Atlas Scientific customer support for assistance.
Calibration order
If this is your first time calibrating the EZO Complete-pH, we recommend
following this calibration orde
Calibration solutions
The Atlas Scientific EZO Complete-pH can work with any brand or value of
calibration solution. We recommend using calibration solutions that have
simple values.
While you can use calibration solutions with complex values, we recommend avoiding unnecessary complexity. Unusually specific calibration values should be treated with suspicion.
Best practices for calibration
Always watch the readings throughout the calibration process. Issue
calibration commands once the readings have stabilized.
Never do a blind calibration!
Issuing a calibration command before the readings stabilize will result in
drifting readings.
Best practices for calibration
Avoid extended stabilization time.
Letting the probes pre-calibrtion readings stabilize over an extended period will cause your calibrated readings to take a long time to stabilize.
Avoid frequent recalibrations.
if it ain’t broke, don’t fix it.
pH probes lose accuracy slowly. Frequent recalibrations (to ensure high accuracy), will often have the opposite effect. It is far more likely that you will misscalibrate the probe than improve its accuracy
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Mid point calibration
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Low point calibration
-
High point calibration
Optional steps:
Confirm your calibration accuracy using the slope command. Recalibrate a single point if required.
Understanding pH slope
The slope function is a powerful tool used to verify calibration and determine the overall health of a pH probe. By evaluating the slope of a pH probe’s response curve, you can determine how well a pH probe was calibrated or when that probe is reaching end of life.
Slope and calibration are directly related. The slope is updated when a calibration command is given. The slope does not update automatically
Generally speaking, all pH probes behave the same way. This means a probe’s
response to calibration can be compared to a simulated pH probe that is
mathematically perfect in all ways.
The slope is broken into three sections; acid, base, and neutral. Each section is evaluated separately
- Acid (pH 1 – 6.9)
- Base (pH 7.1 – 14)
- Neutral (pH 7)
An uncalibrated pH probe will have a mathematically perfect slope. Because no pH probe is mathematically perfect, the slope can be used to determine if the pH was calibrated
Uncalibrated slope : 100, 100, 0 (acid, base, neutral)
% % mV
The first two numbers are percentages, and the third is millivolts. The slope shows that the probe’s response to acid and base is 100% correct, and it detects 0 mv in a pH 7. Because such perfection does not exist in the real world, we know this probe was not calibrated.0
Understanding pH slope
pH 7 is the absence of pH; it is not an acid or a base. Therefore it should
always be your first calibration point. It is equivalent to the tare function
on a scale because it establishes the probe’s zero point.
After pH 7 calibration, use the slope command to see how the probe performed during calibration.
The slope after pH 7 calibration : 100, 100, -1.2
Here we see the probe reads -1.2mV in pH 7. The closer this number is to 0, the better. A new pH probe should give a millivolt offset no greater than -5mV to 5mV. Over time this number’s distance to 0 may increase; the larger the number, the lower the accuracy. A reading >10mV will result in noticeable performance issues.
It is important to remember that a high number is not definitive evidence that the probe is inaccurate or malfunctioning. It is very common to see a high number if the calibration solution was contaminated and not actually its stated value.
The next two calibration points (pH 4 and pH 10) report their slope in percentage. A new pH probe should have a slope of >95%.
- The slope after pH 4 calibration : 98.2, 100, -1.2
- The slope after pH 10 calibration : 98.2, 97.8, -1.2
Tips:
Throughout this explanation, we have looked at the slope after each calibration event. This is unnecessary; in reality, it is best to fully calibrate the probe and look at the slope once calibration has been completed.
To gain a deeper understanding of how slope affects the stability and accuracy
of a pH probe, intentionally miscalibrate the probe and see how it affects the
slope.
