ISFET with built-in calibration registers through segmented eight-bit binary search in three-point algorithm using FPGA

The calibration of chemical sensors is done manually or wherever the sensor is actually deployed. There are certain procedures that should be accurately followed, otherwise the pH measurement will produce an incorrect output. The main purpose of this paper is to create the circuit of an Ion-Sensitive Field-Effect Transistor (ISFET) with built-in calibration registers through segmented eight-bit binary search in three-point algorithm using FPGA. The circuit used the three-point calibration algorithm and the three standard buffers pH4, pH7, and pH10. The block diagram, schematic diagram, and the number of logic gates were derived after synthesizing the Verilog program in Xilinx/FPGA. An average of 0.30% error was computed to prove reliability of the created circuit in FPGA. Having an ISFET with built-in calibration registers will ease the work of the experts in performing calibrations and could be used as a pH level meter or a remote sensor node in several applications.