As shown in FIG. 11, a low-drift differential amplifier 172 receives signals from nodes 160 and 168 of Wheatstone bridge 158 and outputs a signal to a microprocessor 174, which is configured with an ADC. Microprocessor 174 is in signal communication with a non-transient computer readable storage medium 176, such as a RAM, a flash memory, or other storage device, and with a communication module 178