Joulescope JS320 Datasheet#

The Joulescope™ JS320 is a precision DC energy analyzer. It measures current and voltage, then computes power, energy and charge. It measures current over ten orders of magnitude, from amps down to nanoamps, with fast autoranging and minimal voltage drop.

  • ±15V voltage range

  • ±3A current range, continuous

  • ±10A current pulses (<10 ms, < 3A average per second)

  • Down to 0.1 nA resolution, equivalent to 36-bits of dynamic range

  • Synchronously measures voltage and current at 1 million samples per second, 24-bit

  • 200 kHz linear phase bandwidth

  • 300 kHz compensated bandwidth with optional digital filter

  • Rapid 1 μs switching between shunt resistors

  • Enwavify™ technology for consistent, accurate measurements through current range changes

  • Computes power, energy, and charge

  • Operates with minimal voltage disturbance between Current + and Current – ports

  • Up to ±48V common-mode voltage between USB ground and sensing ports

  • 4 general-purpose inputs and 2 general-purpose outputs

  • 1 BNC trigger configurable for either digital input, digital output, or analog output

  • Programmable on/off for power cycling the target device and measuring inrush currents

  • USB 2.0 high-speed host connectivity with USB C connector

  • Host software support for Microsoft® Windows®, Apple® macOS®, and Linux®

  • Host software user interface provides real-time graphs of current, voltage, and power over time

  • Python library and scripting provided

  • Host software is open source and available on GitHub

  • Swappable front panel with open-source designs on GitHub

  • Firmware upgradable

The Joulescope JS320 User’s Guide describes how to use the instrument. The specification values are also available as js320.yaml.

Absolute maximum ratings#

Min

Max

Unit

USB voltage

-0.3

6

V

Max voltage applied between any port (Current +, Current -, Voltage +, Voltage -)

-20

20

V

Max voltage to USB ground from any port (Current +, Current -, Voltage +, Voltage -)

-48

48

V

Input current (powered, burst)

-10

10

A

Input current (powered, sustained)

-3

3

A

Input current (unpowered)

N/A (off)

N/A (off)

A

Storage temperature

-40

80

°C

Operating temperature

0

50

°C

Relative humidity (non-condensing)

0

95

%

Altitude from sea level

-100

2500

m

Max voltage applied to GPI relative to USB ground

-10

10

V

Mechanical#

Instrument only#

Typical

Unit

Weight

190

grams

Width

99

mm

Length (including binding posts and BNC connector)

126

mm

Height

28

mm

Complete product kit#

Typical

Unit

Weight

510

grams

Width

190

mm

Length

200

mm

Height

60

mm

Specification conditions#

Temperature

23 °C ± 10 °C

Humidity

20% to 80% RH, non-condensing

Calibration interval

1 year1

  1. Recommended to comply with industry-standard practices, but the Joulescope JS320 is designed not to need recalibration.

Current measurement specifications#

Range

Accuracy1

Impedance

Guaranteed2

10 A3

±0.25% ±500 µA

0.01 Ω

±10.4 A

180 mA

±0.25% ±50 µA

0.11 Ω

±188 mA

18 mA

±0.25% ±5 µA

1.11 Ω

±18.8 mA

1.8 mA

±0.25% ±500 nA

11.1 Ω

±1.88 mA

180 µA

±0.25% ±50 nA

111 Ω

±188 µA

18 µA

±0.25% ±10 nA4

1111 Ω

±18.8 µA

  1. Accuracy is specified as a percentage of measurement plus a fixed offset. Some instruments specify offset as a percentage of the full-scale range.

  2. The highest current that this range is guaranteed to measure without saturation. Higher currents may saturate the range and potentially trip the soft fuse for that current range.

  3. Max 3 A sustained. See the recommended operating conditions for higher current durations.

  4. ±1.0 nA for ±5 °C over 24 hours with trim offset calibration.

The resolution depends on the noise. Noise depends on both the current range and signal bandwidth, which is limited by the sample frequency. The following table shows the typical (not guaranteed) resolution given only the JS320 self-noise with no additional external noise pickup.

Range

1 Msps resolution (typical)

10 ksps resolution (typical)

10 sps resolution (typical)

Units

10 A

1000

100

10

µA

180 mA

100

10

1

µA

18 mA

10

1

0.1

µA

1.8 mA

1000

100

10

nA

180 µA

100

10

1

nA

18 µA

10

1

0.1

nA

Test current measurement bandwidth by varying the effective load impedance. Due to load capacitance, altering the source voltage is often not a valid method of testing current bandwidth.

The JS320 is sensitive to RF radiation, which induces real current in test setups. When tested with EN61326-1 and 3 V RMS/m, the JS320 measured up to 10 µA (observed, not guaranteed) of current at several frequencies. The exact frequency susceptibility varies with cable length and configuration.

Voltage measurement specifications#

Range

Accuracy1

Guaranteed

15 V

±0.1% ±500 µV

±15.5 V

2 V

±0.1% ±200 µV

±2.05 V

  1. At V+ == I+. See the CMRR specification for extended voltage.

The resolution depends on the noise. Noise depends on both the current range and signal bandwidth, which is limited by the sample frequency. The following table shows the typical (not guaranteed) resolution given only the JS320 self-noise with no additional external noise pickup.

Range

1 Msps resolution (typical)

10 ksps resolution (typical)

10 sps resolution (typical)

Units

15 V

500

50

10

µV

2 V

100

10

2

µV

The JS320 is sensitive to RF radiation, which induces real voltages in test setups. When tested with EN61326-1 and 3 V RMS/m, the JS320 error increased by 10 mV (observed, not guaranteed) at several frequencies. The exact frequency susceptibility varies with cable length and configuration.

General specifications#

Test condition

Min

Typical

Max

Unit

Sampling frequency

25 °C

1000000

sps

Sampling frequency accuracy

25 °C

-5

5

ppm

Measurement bandwidth

-3 dB

185

195

225

kHz

Compensated bandwidth

-3 dB

280

300

350

kHz

Front panel insertions

100

Parasitic effects specifications#

Test condition

Min

Typical

Max

Unit

Current leakage (Voltage + to -)

25 °C, ±3.3V

100

pA

Current leakage (Voltage + to -)

25 °C, ±5V

100

pA

Current leakage (Voltage + to -)

25 °C, ±15V

100

pA

Shunt resistor voltage, max

-2 to 2 A, static

20

21

mV

Burden voltage (Current + to -)

1 A, banana jacks

0

25

35

mV

Burden voltage (Current + to -)

Shunt resistor, < ±2 A

±20

mV

Shunt switching time

Over-range, < 200 ns rise time

0

0.8

1.2

µs

Measurement gap following a current range switch

0

µs

CMRR on voltage input (common mode rejection ratio)

25 °C, ±15V

-70

dB

Software-controlled fuse specifications#

Test condition

Min

Typical

Max

Unit

Current leakage (Current + to -)

25 °C, 3.3V

±5

nA

Current leakage (Current + to -)

25 °C, 5V

±7

nA

Current leakage (Current + to -)

25 °C, 15V

±28

±5000

nA

Fuse engage time

5 A

0.293

s

Fuse engage time

10 A

0.050

s

General purpose inputs and outputs#

Test condition

Min

Typical

Max

Unit

Internal 3.3V reference

3.135

3.3

3.465

V

External reference

Vref < (VUSB - 0.5 V)

Vref - 0.1

Vref

Vref + 0.1

V

Input leakage per pin

25 °C

±10

nA

Input leakage per pin

±100

nA

Output voltage high

-100 µA

Vcco - 0.1

V

Output impedance

10 mA

45

50

80

Ω

GPI sample rate

1

MSPS

Continuous output current

Per pin

±50

mA

Total power dissipation

Over output impedance

0.25

W

The Joulescope uses the TI TLV9034 for GPIs and the TI SN74LVC2T45 to drive the GPOs. Both the GPIs and GPOs are protected with the TI TPD4E1U06 for ESD protection.

Both gates of the TI SN74LVC2G125 drive the trigger in parallel, each through a 100 Ω resistor for 50 Ω drive.