I am new to this forum but not to op-amps. I would like to know if the Arduino Mega can do what the INA125 (instrumentation amplifier) does almost (but making a digital output number) sitting at the null point of a wheatstone bridge. I imagine using the analogReference command and some kind of differential input (hopefully the reference input is an internal voltage) and using one of the rumored gains (5, 10, 20, 40).
I do not see any commands for this in the C language reference. This is unfortunate because I am using the easily understood C that the Mega uses and so far everything is written in C.
My present input is a 1K resistor in series with a 1K ohm RTD (yes it is not the 100 ohm standard RTD) generating 2.5Vdc. If I have to make the other side of the wheatstone bridge with real resistors and use an op-amp to increase the gain, then that will work but it is considered to be a failure.
Once again what I need is the C instruction keywords and maybe an example showing how to use them. I am already familiar with analogRead and analogReference. I need something additional.
The ADC in the atmel mega328 chip's internal ADC hardware supports single-ended inputs only, there is no differential input suitable for measuring across the null point of a DC excited Wheatstone bridge arrangement. There are ways to lower the ADC reference voltage used by the ADC to get smaller resolution step size over a reduced ground to reference voltage measurement range but that is not the same as having differential input capabilities. There are simple to use external I2C ADC chips that have differential inputs, programmable gains, better resolution, etc available such as:http://www.adafruit.com/products/1085http://www.adafruit.com/products/1083
Once again what I need is the C instruction keywords and maybe an example showing how to use them.
I think you are mixing apples and oranges here. The C/C++ programming language keywords have nothing to do with any specific support for anyone's hardware features. Such hardware features must have user or IDE implementers custom written C/C++ functions or libraries written to support a specific microcontrollers hardware features. That's what analogRead() is, a custom written function that knows how to manipulated the internal ADC hardware inside AVR chips supported by the arduino IDE. They are not considered C/C++ 'key words' but rather are functions and library that can be used in programs written in C/C++.