Liquid PH0-14 Value Detect Sensor Module + PH Electrode Probe BNC for Arduino (PH Sensor and Module)

I tried every calibration method in arduino code I can find but still not getting accurate readings. The reason is the first stepin calibrating is shorting the probe connector and adjusting output to 2.5V. Can not adjust below 2.83V for some reason. Also there seem to not bet any led indicators on the module board.The remedy was to adjust the module output to the center of its output range (2.83-4.83) which is 3.83. Then I used 4.01 and 6.86 test solutions to get the voltage readings I need Then I used 4.01 and 6.86 test solutions to get the voltage readings I needed to do the slope equation. Once I did that I took the C and m products of the slope equation and entered them into my arduino code. Now my ph values are smack on!! Working perfectly!

I ended up going with the pH gravity sensor from DFRobot (atlas scientific makes one too) because it outputs 0 to 5 volts where a neutral pH of 7 is 2.5 volts (pH 0 is 5 volts and pH 14 is 0 volts) whereas this pH meter outputs negative for a pH under 7 and positive for above 7). You can adjust the gain on this probe to change that but it loses a lot of accuracy. This module is so inaccurate that after calibration it was reading calibration solution off by 1 pH number. Not to mention there is no documentation or support, I tried contacting support for a data sheet and got no response twice.