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Integrate energy and charge over time, or compute current/voltage/power statistics, using a Joulescope JS220 connected to a Lager Box.

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Syntax

lager energy [OPTIONS] NET_NAME
lager energy stats [OPTIONS] NET_NAME

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Commands

CommandDescription
lager energyIntegrate energy and charge over a duration
lager energy statsCompute mean/min/max/std for current, voltage, and power

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lager energy

Integrate current and power over a configurable duration. Returns energy in joules and watt-hours, and charge in coulombs and amp-hours.

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Options

OptionDescription
--box BOXLagerbox name or IP address
--duration FLOATIntegration duration in seconds (default: 10.0)
--helpShow help message and exit

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Arguments

ArgumentDescription
NET_NAMEName of the energy-analyzer net (optional if default is set)

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Output

Energy 'POWER_METER' (10.0s):
  Energy:  12.500 mWh  (45.000 mJ)
  Charge:  3.472 mAh   (12.500 mC)

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Examples

# Integrate over the default 10 seconds
lager energy POWER_METER --box my-box

# Integrate over 60 seconds
lager energy POWER_METER --box my-box --duration 60

# Use the default net
lager energy

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lager energy stats

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

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Options

OptionDescription
--box BOXLagerbox name or IP address
--duration FLOATMeasurement duration in seconds (default: 1.0)
--helpShow help message and exit

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Arguments

ArgumentDescription
NET_NAMEName of the energy-analyzer net (optional if default is set)

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Output

Stats 'POWER_METER' (1.0s):
  Current (A):  mean=0.015200  min=0.014900  max=0.015600  std=0.000120
  Voltage (V):  mean=3.301000  min=3.300500  max=3.301500  std=0.000200
  Power   (W):  mean=0.050175  min=0.049185  max=0.051516  std=0.000400

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Examples

# Stats over the default 1 second
lager energy stats POWER_METER --box my-box

# Stats over 5 seconds for better averaging
lager energy stats POWER_METER --box my-box --duration 5

# Use the default net
lager energy stats

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Default Net

To avoid specifying the net name each time: 
lager defaults add --energy-net POWER_METER
Then: 
lager energy
lager energy stats

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Supported Hardware

ManufacturerModelNet TypeUSB VID:PID
JoulescopeJS220energy-analyzer16d0:10ba
The energy-analyzer net type is exclusive to the Joulescope JS220. For instantaneous power readings only, see Watt Meter.

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Scripting Examples

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Energy Budget Verification

#!/bin/bash
# Verify a device's energy consumption during a 10-second test
RESULT=$(lager energy POWER_METER --box my-box --duration 10)
echo "$RESULT"

# Extract mWh value for pass/fail
MWH=$(echo "$RESULT" | grep -oP '[\d.]+(?= mWh)')
if (( $(echo "$MWH > 50" | bc -l) )); then
    echo "FAIL: Energy consumption too high: ${MWH} mWh"
    exit 1
fi
echo "PASS: Energy within budget"

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Sleep Current Verification

#!/bin/bash
# Check sleep current is below 100 uA
RESULT=$(lager energy stats POWER_METER --box my-box --duration 5)
echo "$RESULT"

# Extract mean current in amps, convert to uA
CURRENT_A=$(echo "$RESULT" | grep "Current" | grep -oP 'mean=\K[\d.]+')
CURRENT_UA=$(echo "$CURRENT_A * 1000000" | bc -l)

if (( $(echo "$CURRENT_UA > 100" | bc -l) )); then
    echo "FAIL: Sleep current ${CURRENT_UA} uA exceeds 100 uA limit"
    exit 1
fi
echo "PASS: Sleep current ${CURRENT_UA} uA"

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Troubleshooting

ErrorCauseFix
Timeout (120s)Device disconnected or measurement too longCheck USB connection; reduce --duration
Connection refusedBox service not runningCheck box: lager hello --box <box>
Device not foundJoulescope JS220 not detectedVerify device is connected: lager instruments --box <box>
Net not foundNet not configured as energy-analyzerCheck net type: lager nets --box <box>

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Notes

  • The default command timeout is 120 seconds to accommodate long integrations
  • Joulescope JS220 samples continuously; accuracy improves with longer durations
  • Use lager instruments --box <box> to verify the JS220 is detected (VID 16d0 PID 10ba)
  • Net names refer to names assigned when configuring your testbed
  • Use lager nets to see available energy-analyzer nets