Atlas Scientific EZO EC Calibration Procedure

About: Founded in 2005, Atlas Scientific specializes in building laboratory grade sensing equipment for robots, appliances, and industrial control systems. Thousands of Atlas Scientific sensors can be found in a wi...

Theory

The most important part of calibration is watching the readings during the calibration process. It is easiest to calibrate the device in its default state (UART mode, with continuous readings enabled). 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 continuously request readings so you can see the output from the probe. For instructions on how to change between protocols refer to: How to change data protocol of Atlas sensors

The Atlas EZO EC circuit has a flexible calibration protocol, allowing for single-point or two-point calibration. Two-point calibration will provide a wider range of accuracy.

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Step 1: Set Probe Type and Do a Dry Calibration

Probe Type

If the probe is not K1.0, then set the probe type by sending the command k,n where n is the k value of the probe.

Dry Calibration

This is a necessary part of the calibration process and must be done before the single point of two-point calibration.

a) Enable continuous readings by sending the command c,1 which will output a reading every second.

b) Ensure that the probe is dry. With the probe in air, issue the command cal,dry

Step 2: Two Point Calibration - Low Point

a) Pour some of the 12880µS calibration solution into a cup. Ensure that there is enough solution to cover the sensing area of the probe.

b) Place the probe into the cup and stir it around to remove trapped air. Let the probe sit in the solution. Readings maybe off by +/- 40% from the stated value of the calibration solution.

c) Wait for readings to stabilize (small movement from one reading to the next is normal) and send the command cal,low,12880

Note: The readings will not change after this command is entered.

Step 3: Two Point Calibration - High Point

a) Rinse off the probe before calibrating to the high point.

b) Pour some of the 80000µS calibration solution into a cup. Ensure that there is enough solution to cover the sensing area of the probe.

c) Place the probe into the cup and stir it around to remove trapped air. Let the probe sit in the solution. Readings may be off by +/- 40% from the stated value of the calibration solution.

d) Wait for readings to stabilize (small movement from one reading to the next is normal) and send the command cal,high,80000

Note: The readings will change after this command is entered. Calibration is now complete.

Step 4: Single Point Calibration

a) Pour some calibration solution into a cup (μS value of your choice). Ensure that there is enough solution to cover the sensing area of the probe.

b) Place the probe into the cup and stir it around to remove trapped air. Let the probe sit in the solution. Readings maybe off by +/- 40% from the stated value of the calibration solution.

c) Wait for readings to stabilize (small movement from one reading to the next is normal) and send the command cal,n where n is the value of the calibration solution. Note: Readings will change after the command is entered. Calibration is now complete.

Step 5: Temperature Compensation During Calibration

Temperature has a significant effect on conductivity/salinity readings. The EZO conductivity circuit has its temperature set to 25 ̊ C as the default.

At no point should you change the default temperature compensation during calibration.

If the calibration solution is +/- 5 ̊ C (or more), refer to the chart on the bottle and calibrate to the corresponding value.

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