Digital display for half wave detector with cubic spline interpolation – part 1 and following articles laid out the design concepts of a power meter display.
Whilst the preferred target was an Arduino Zero (SAMD21G) for its 32bit architecture, speed, and 12bit ADC, the code was developed to run on a Zero or a Arduino Nano (ATmega328P).
This article explores a trial of an external ADC module using an ADS1115 chip, 4 channels 16bit +/- ADC.
Above is the prototype, Arduino Nano on the left, the ADS1115 module is to the right of the display.
The code is running averaging four successive readings and refreshes the display twice per second.
This is far and away the lowest noise solution, with a short circuit on the ADC input, noise is around10/32768 or -70dBfs. The noise floor of a completed prototype will be interesting.
The cubic spline fit is a very good approximation of the detector response, measurement of a completed prototype will inform.
Next step is to evaluation ADC noise on some more dev board candidates (another Arduino Zero board coming).
Continued at Digital display for half wave detector with cubic spline interpolation – part 4.
A work in progress..