Energy Analyzer

Integrate energy and charge, and compute power statistics using an energy-analyzer net

Integrate energy and charge over time, or compute current/voltage/power statistics, from an energy-analyzer net. Requires the energy-analyzer net type.

Import

from lager import Net, NetType

Methods

Method	Description
read_energy(duration)	Integrate energy and charge over duration seconds
read_stats(duration)	Compute mean/min/max/std for current, voltage, and power

Method Reference

Net.get(name, type=NetType.EnergyAnalyzer)

Get an energy analyzer net by name.

from lager import Net, NetType

power = Net.get('POWER_METER', type=NetType.EnergyAnalyzer)

Parameters:

Parameter	Type	Description
name	str	Name of the energy-analyzer net
type	NetType	Must be NetType.EnergyAnalyzer

Returns: Energy analyzer Net instance

read_energy(duration)

Integrate current and power over duration seconds.

result = power.read_energy(10.0)
print(f"Energy: {result['energy_wh'] * 1000:.3f} mWh")
print(f"Charge: {result['charge_ah'] * 1000:.3f} mAh")

Parameters:

Parameter	Type	Description
duration	float	Integration window in seconds

Returns: dict with keys:

Key	Type	Description
"energy_j"	float	Energy in joules
"energy_wh"	float	Energy in watt-hours
"charge_c"	float	Charge in coulombs
"charge_ah"	float	Charge in amp-hours
"duration_s"	float	Duration that was requested

read_stats(duration)

Compute mean, minimum, maximum, and standard deviation for current, voltage, and power over duration seconds.

stats = power.read_stats(1.0)
print(f"Current: {stats['current']['mean'] * 1e6:.1f} uA (mean)")
print(f"Voltage: {stats['voltage']['mean']:.3f} V (mean)")
print(f"Power:   {stats['power']['mean'] * 1000:.3f} mW (mean)")

Parameters:

Parameter	Type	Description
duration	float	Measurement window in seconds

Returns: dict with keys:

Key	Type	Description
"current"	dict	Current statistics in amps
"voltage"	dict	Voltage statistics in volts
"power"	dict	Power statistics in watts
"duration_s"	float	Duration that was requested

Each statistics sub-dict contains:

Key	Type	Description
"mean"	float	Mean value
"min"	float	Minimum value
"max"	float	Maximum value
"std"	float	Standard deviation

Examples

Energy Budget Check

from lager import Net, NetType

power = Net.get('DEVICE_POWER', type=NetType.EnergyAnalyzer)

result = power.read_energy(10.0)

energy_mwh = result['energy_wh'] * 1000
charge_mah = result['charge_ah'] * 1000

print(f"Energy: {energy_mwh:.3f} mWh")
print(f"Charge: {charge_mah:.3f} mAh")

if energy_mwh > 50:
    print("FAIL: Energy consumption exceeds budget")
else:
    print("PASS: Energy within budget")

Sleep Current Verification

from lager import Net, NetType

power = Net.get('DEVICE_POWER', type=NetType.EnergyAnalyzer)

# Measure over 5 seconds for accuracy
stats = power.read_stats(5.0)

sleep_ua = stats['current']['mean'] * 1e6
supply_v = stats['voltage']['mean']

print(f"Sleep current: {sleep_ua:.1f} uA")
print(f"Supply voltage: {supply_v:.3f} V")

if sleep_ua < 100:
    print("PASS: Sleep current below 100 uA")
else:
    print(f"FAIL: Sleep current {sleep_ua:.1f} uA exceeds 100 uA limit")

Battery Life Estimation

from lager import Net, NetType

power = Net.get('DEVICE_POWER', type=NetType.EnergyAnalyzer)

# Measure average current draw over a representative workload
stats = power.read_stats(30.0)

avg_current_ma = stats['current']['mean'] * 1000
avg_voltage_v = stats['voltage']['mean']

# Estimate from a 1000 mAh battery
battery_mah = 1000
hours = battery_mah / avg_current_ma if avg_current_ma > 0 else float('inf')

print(f"Average current: {avg_current_ma:.3f} mA")
print(f"Average voltage: {avg_voltage_v:.3f} V")
print(f"Estimated battery life: {hours:.1f} hours")

Startup Energy Capture

from lager import Net, NetType

power = Net.get('DEVICE_POWER', type=NetType.EnergyAnalyzer)

# Capture energy consumed during device startup (2 seconds)
result = power.read_energy(2.0)

print(f"Startup energy: {result['energy_j'] * 1000:.2f} mJ")
print(f"Startup charge: {result['charge_c'] * 1000:.2f} mC")

Current Spike Analysis

from lager import Net, NetType

power = Net.get('DEVICE_POWER', type=NetType.EnergyAnalyzer)

# Short window to capture peak current
stats = power.read_stats(1.0)

peak_ma = stats['current']['max'] * 1000
avg_ma = stats['current']['mean'] * 1000
std_ma = stats['current']['std'] * 1000

print(f"Peak current:    {peak_ma:.3f} mA")
print(f"Average current: {avg_ma:.3f} mA")
print(f"Std deviation:   {std_ma:.3f} mA")

# Flag if peak is more than 10x average (unexpected spike)
if peak_ma > avg_ma * 10:
    print("WARNING: Unexpected current spike detected")

Supported Hardware

Manufacturer	Model	Net Type	USB VID:PID
Joulescope	JS220	energy-analyzer	16d0:10ba
Nordic Semiconductor	PPK2	energy-analyzer	1915:c00a

For instantaneous power readings (also available on Yocto-Watt), see Watt Meter.

Notes

• The Joulescope JS220 samples at high frequency; longer durations yield more accurate statistics
• The Nordic PPK2 operates in source mode (supplies a configurable voltage 0.8–5V and measures current); voltage readings reflect the configured value
• read_energy() and read_stats() block for the full duration before returning
• The same physical JS220 device is shared between WattMeter and EnergyAnalyzer net roles — opening both net types for the same device is safe
• Use lager instruments --box <box> to verify the JS220 is detected before running scripts