What Is Hardware Reliability Testing

What Is Hardware Reliability Testing with TofuPilot

Hardware reliability testing stresses a product beyond normal conditions to find failure modes before customers do. It predicts how long a product will last and which components fail first. This guide covers the main reliability test methods, how to build reliability test scripts in Python, and how to track results with TofuPilot.

Why Reliability Testing Matters

Production test tells you a unit works right now. Reliability testing tells you it will still work in six months, two years, or ten years. The cost difference between finding a failure mode in the lab versus in the field is typically 10x to 100x.

Reliability testing is required or expected in:

• Medical devices (FDA 21 CFR Part 820)
• Aerospace (DO-160, MIL-STD-810)
• Automotive (AEC-Q100/Q200, IATF 16949)
• Consumer electronics (IEC 60068, JESD22)

Common Reliability Test Methods

HALT vs ALT

HALT is qualitative: you're looking for weak spots. ALT is quantitative: you're predicting how long the product lasts.

Prerequisites

• Python 3.10+
• OpenHTF installed (pip install openhtf)
• TofuPilot Python SDK installed (pip install tofupilot)

Step 1: Define Reliability Check Phases

Reliability tests often run a functional check between stress cycles. This detects degradation over time.

import openhtf as htf
from openhtf.util import units


@htf.measures(
    htf.Measurement("output_voltage_V")
    .in_range(
        minimum=3.0, maximum=3.6,
        marginal_minimum=3.1, marginal_maximum=3.5,
    )
    .with_units(units.VOLT),
    htf.Measurement("current_draw_mA")
    .in_range(minimum=40, maximum=65)
    .with_units(units.MILLIAMPERE),
)
def phase_functional_check(test):
    """Run after each stress cycle to detect degradation."""
    test.measurements.output_voltage_V = 3.31
    test.measurements.current_draw_mA = 49.8


@htf.measures(
    htf.Measurement("insulation_resistance_MOhm")
    .in_range(minimum=100)
    .with_units(units.OHM),
)
def phase_insulation_check(test):
    """Verify insulation resistance hasn't degraded."""
    test.measurements.insulation_resistance_MOhm = 450.0

Step 2: Log Each Cycle to TofuPilot

Run the functional check after every stress cycle and log it as a separate test run. This creates a timeline of measurements per unit that shows degradation trends.

from tofupilot.openhtf import TofuPilot

test = htf.Test(
    phase_functional_check,
    phase_insulation_check,
)

with TofuPilot(test):
    test.execute(test_start=lambda: input("Scan unit serial: "))

Run this script after each temperature cycle, vibration session, or time interval. Each execution creates a new test run linked to the same serial number.

Step 3: Track Degradation in TofuPilot

TofuPilot tracks every run per serial number. Open the unit history to see:

• Measurement trends over time for each unit (voltage drift, current increase)
• Marginal results flagged before hard failures occur
• Control charts showing when a parameter starts trending toward a limit
• Failure analysis identifying which phase fails first across the test lot

This data feeds directly into reliability reports. Instead of pulling numbers from chamber logs and multimeter screenshots, the full test history lives in one place.

When to Use Each Method

Reliability testing is an investment. Start with HALT in EVT to find the obvious failures, then run ALT in DVT to quantify the margins. By PVT, your design should survive the stress levels your customers will see.