Walk through the steps to perform an automatic two-point pH calibration using the Stratos Evo transmitter from Knick with a Memosens pH sensor.

Memosens Benefits

The main benefit of using Memosens digital sensors is that the calibration data stores in the sensor head and not in the transmitter. This allows us to save time by pre-calibrating our sensors and storing them on the shelf. We can now perform our calibrations offline in a controlled environment right here in our workshop. You can also follow these same steps when performing a calibration in the field.

What You Need

To perform a calibration you will need: a Stratos Evo transmitter that has been powered up with a Memosens cable connected, a Memosens pH sensor, at least two buffers and clean containers to pour them into, cleaning water, and finally a clean cloth to dry the sensor.

Connecting Your Sensor

Let’s begin by connecting our Memosens pH sensor pressing the Menu button and then toggling right to the calibration screen. Here you will see our three options for calibrating the sensor: Cal_pH, P Cal or process calibration, and finally Cal_ RTD or calibration of the internal temperature detector. We will select Cal pH to begin the process.

Buffer Sets

Since we’re performing an automatic calibration, it’s very important to select the proper buffer sets when configuring the transmitter. Automatic calibration ensures that the buffer sets are temperature compensated and they’re automatically recognized during the process. If you’re not sure where to select the proper buffer set, please be sure to view our Setup and Configuration video on the Stratos Evo.

Beginning the Calibration

Once the calibration process begins you can see that our transmitter screen turns yellow. The hold icon also indicates that our output to our control room is on hold. First we will rinse our sensor with distilled water and dab dry with a clean cloth. I’m using Knick Calimat at buffers with integrated dosing cup for single dose usage. If you’re not using Knick Calimat buffers, be sure to put your buffers in separate clean containers to prevent cross-contamination and for a more accurate calibration. We recommend using fresh buffer solution for each calibration.

First Buffer

Let’s place our sensor in the first buffer solution and stir lightly. We want to be sure to fully immerse the entire pH measuring bulb along with the sensor’s junction in the buffer. Also make sure that both the pH value and the temperature value at the bottom of the screen have stabilized. In automatic calibration mode, the transmitter will display the recognized buffer value as well as the millivolt value. Once complete with the first buffer solution, the zero point of our sensor is displayed. The Stratos Evo now prompts us to move to the second step in the calibration process.

Second Buffer

We’ll press Enter to continue. Next, we should again rinse our sensor with distilled water and dab dry. Place the sensor in the second buffer solution stir lightly and again, be sure to completely immerse the bulb and the junction. Just like in our first buffer solution, it’s important to let both the pH and temperature value stabilize. We’ll then press Enter. Again, the transmitter automatically recognizes the buffer value, and it also displays our millivolt value.

Finalizing the Calibration

Once the process is completed, in our second buffer solution you’ll see that the Stratos Evo then provides the specific information of our calibration. First, it displays our slope in percentage. Next, it displays our zero point in millivolts and finally, a smiley face indicates a successful calibration. Press Enter and the Stratos Evo will now give us the opportunity to repeat our calibration process or write the calibration to our sensor by selecting Measure.

Pressing Enter on Measure also finalizes the calibration process and returns us to the main measurement screen. We’re now ready to go on-line with our measurement or store our calibrated sensor on the shelf for future use in the field. Thank you for watching and be sure to check out our other videos on the Stratos Evo transmitter.