A digital power-quality meter: communication, sensing, calibration and the numbers on the screen.
The reference drawing and the ADS1115 program follow different routes. The drawing names ESP-WROOM-32, takes the sensor signals into the controller's ADC inputs and shows I²C serving an LCD. The application reads an external ADS1115 over I²C instead. I find the comparison useful because the pur
The calibration pairs are literal differences between saved versions. The report and smaller RMS sketch contain 769.0 and 0.85. The final-named file contains 766.0 and 0.85, while another copy contains 625.0 and 30.0. I can compare those actual values without assuming that three files represent
Delay(500) looks quite ordinary at the end of the raw sampler. Against a 50 Hz waveform, it is a long wait: half a second contains 25 ideal cycles. Before that wait, the sketch reads A0 and A1, converts them with computeVolts and prints counts beside input volts. That makes its purpose clearer
The four saved sketches give me four ways to look at the meter. The scanner searches for replies, the raw sampler prints counts and input volts, the RMS program works through separate collections, and the full meter combines stored readings into more quantities. I like the fact that their jobs
The first build began in June 2025 and took about four months in my project notes. Looking back at the saved work, I can give that period a more particular shape: communication with the ADC, trouble with temporary connections, the move to perfboard and the mathematics that gives sampled values
The RMS loop gives me a particular explanation to try in my own words. A reading becomes input volts, the offset is removed, its square joins a running total, and that total is averaged and rooted. Then a calibration factor supplies the sensor scale. I can point to each operation in the saved p
The display precision is chosen in Serial.printf. Voltage and power get two decimal places, current gets three, and power factor and crest factor get three. I find that a useful detail to remember while looking at the complete output: printed digits are a formatting choice, while their physical
The peak in the final sketch is the largest absolute calibrated voltage sample. fabs makes the convention explicit: both positive and negative excursions can supply the magnitude. The program divides that peak by RMS only when RMS voltage is above 10 V, otherwise returning zero. I can connect t
The saved frequency rule counts one direction of crossing. A previous centred voltage sample must be below zero and the next at or above it. After the collection, the program uses the crossing count minus one divided by the duration of the whole acquisition. Those are definite choices I can fol
The reactive-power expression sits behind a definite condition in the saved file. reactive_power begins at zero, and the program calculates the square root of S squared minus P squared only when apparent power is greater than active power. I can study that choice alongside the familiar power tr
The ratio in the saved code is active power divided by apparent power. That gives me a particular way to examine the word efficiency in the plot in the report's power-factor title. Both inputs to the ratio come from electrical measurements; there is no useful-output measurement in that calculat
The full program takes two different routes to a power value. For active power, it adds calibrated voltage-current products and averages them. For apparent power, it multiplies the separate RMS results. I can locate both operations in the code, which makes the W and VA labels much easier to exp
The final gate changes more than the current display. When i_rms is strictly below 0.05 A, the code sets both current and active power to zero before calculating apparent power. That gives a displayed zero a specific software explanation. The smaller RMS version has another route: it gates curr
The calibration guide gives a concrete adjustment rule: new factor equals old factor times the reference reading divided by the program reading. It gives separate voltage and current versions of that relationship. That’s much more useful to me than treating 769.0 and 0.85 as numbers that simply
The two values share an array index, but they do not come from one simultaneous call. The final sketch reads A0 and then A1 for every entry. Later, their calibrated values are multiplied into sum_p. That’s the precise place where the relationship between voltage and current enters the result. I
