-The client has been updated to version 2.0.4
-calibration PH
-fix PH timers

PH sensor calibration instructions:
1. The sensor is calibrated against two test liquids with a known pH.
2. The pH level of the calibration fluids can be anything (try to use any liquid with a pH between ~ 4.01 and ~ 6.86).
3. We close the signal contact at the BNC connector to ground on the PH-45020 board, while simultaneously connecting the tester in the voltage measurement mode to the P0 output and ground. Rotating the tuning resistor (which is closer to the BNC), we determine the voltage interval in the photo, it is a shaded rectangle.
4. Next, we set the trimmed resistor so that when the sensor's PH is immersed in both liquids, the voltages lie within the voltage range, this is not always the average value. (Point 3-4 is done once during the first setup)
5. Next, immerse the sensor in solution # 1 with a lower pH, wait enough time for the values to stop changing. Press the button "pH solution No. 1" and enter the value of the pH of the liquid in which the sensor is immersed.
6. Rinse the sensor and immerse it in the second solution, perform the same steps 

as in point 5.
7. Calibration is complete.
ps Measurements are based on linear interpolation. Which does not always give high accuracy, but in this case, for our purposes, it is quite a suitable method.
ps. Calibration solutions from China are very inaccurate, you can buy a pH meter for these purposes, although its accuracy will be even lower, but still it is the best option ...