The $2.97 ADC Gamble: When Bargain Hardware Bites Back

For embedded engineers, Texas Instruments' ADS1115 has long been a go-to solution for precision analog-to-digital conversion. With its 16-bit resolution, programmable gain amplifier (PGA), and internal voltage reference, it promises high-fidelity measurements—especially for low-voltage signals where its ±0.256V range delivers 7.8µV precision per LSB. But when James Bowman spotted ADS1115 breakout boards on Amazon for just $2.97 (a fraction of DigiKey's $4/chip price), skepticism set in. What compromises lurk beneath such radical discounts?

Cracks in the Foundation

Initial tests suggested authenticity: The bargain modules delivered true 16-bit outputs, functional PGA adjustments, and correct polarity handling in differential mode. Yet deeper scrutiny exposed alarming flaws:

• Wildly erratic timing: One unit sampled at 300SPS—over 3x faster than its 860SPS spec—injecting noise and violating TI's ±10% data rate tolerance. Others ran slower than permitted.
• Voltage inaccuracies: A calibrated 2.50067V source read as 2.4883V—a 0.5% error versus TI's claimed 0.15% maximum gain error.

Cheap ADS1115 breakout boards like this one showed inconsistent performance

Salvageable—But at What Cost?

A linear correction calibration resolved voltage inaccuracies to within 10µV, proving the hardware isn't useless. But as Bowman notes: "How many end users would actually notice it’s running faster (and hence noisier) than it’s meant to?"* This highlights the invisible risks—uncaught timing flaws could derail sensor integrations or control systems.

The Hobbyist's Dilemma

The units likely originate from LCSC's $0.60 ADS1115s—either counterfeits or factory rejects. With Adafruit's $12.50 (presumably authentic) module en route for comparison, the experiment underscores a harsh reality: ultra-cheap components carry hidden expenses in validation time and reliability risks. For prototyping? Maybe. For production? Potentially catastrophic.

As supply chain opacity grows, Bowman’s probe is a stark reminder: In electronics, price anomalies often signal engineering tradeoffs. When a chip costs less than coffee, skepticism isn't optional—it's essential.

Source: How bad can a $2.97 ADC be? by James Bowman