CT Clamp Burden Resistor Selection and ADS1115 Calibration
Hardware used in this build
- Split-core CT clamp (x2)
JANSANE SCT-013-000 100 A split-core CT clamp. Works, but a split core that is not fully closed reads low silently. Calibration constant is empirically fitted. - ADS1115 16-bit I2C ADC breakout
HiLetgo ADS1115 16-bit 4-channel I2C ADC. Fine for relative load trends; 860 SPS is ~14 samples/cycle at 60 Hz, so harmonics alias. - Raspberry Pi 4
Used in the running shed build; works reliably.
This guide is generated from data/guides.json and data/parts.json. Don’t edit by hand — edit the data.
Comparison
| Part | Role | Interface | Verdict | Price |
|---|---|---|---|---|
| Split-core CT clamp (x2) | Current sensing on both 120 V legs of the panel | Analog into ADS1115 A2/A3 | conditional | — |
| JANSANE SCT-013-000 100 A split-core CT clamp. Works, but a split core that is not fully closed reads low silently. Calibration constant is empirically fitted. | ||||
| ADS1115 16-bit I2C ADC breakout | Reads the two CT clamps (channels A2/A3) for whole-house current | I2C, single-ended A2/A3 | conditional | — |
| HiLetgo ADS1115 16-bit 4-channel I2C ADC. Fine for relative load trends; 860 SPS is ~14 samples/cycle at 60 Hz, so harmonics alias. | ||||
| Raspberry Pi 4 | 1-Wire master + villa collector | dtoverlay=w1-gpio; SQLite timeseries.db | yes | — |
| Used in the running shed build; works reliably. |
Verdict
Pick the part that matches your interface and accuracy needs. If you need humidity, prefer BME280 over BMP180. For long 1-Wire runs, DS18B20 is the most robust choice.
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Related reading
- How to Spot a Fake DS18B20 Temperature Sensor on a Raspberry Pi
Spot a fake DS18B20 on a Raspberry Pi: family-code check, sysfs CRC test, and ice/boil calibration against the datasheet. 3 of 7 probes in one batch were counterfeits, drifting 1.5–3.5 °C.
- SQLite Rollups and Retention: Stop Your Sensor DB From Eating the SD Card
How rollup tables and a retention policy keep a Raspberry Pi sensor SQLite database from growing unbounded — and why SD-card wear is rarely the real problem.
- CT Clamp Burden Resistor Calibration for ADS1115 on Raspberry Pi
CT clamp burden resistor calibration for ADS1115 on Raspberry Pi: pick the external burden, stabilise with a decoupling cap, and apply the DC-bias correction that separates a stable watt reading from drift — with the 51 Ω + 10 µF combination I actually measured.