tinyCurrent – a uCurrent Gold Clone/ Derivative
A low cost yet professional low current measurement shunt and amplifier combination to overcome the issue of high burden voltage as seen with multimeters and to enable low current measurement by using voltage measurement devices such as oscilloscopes.
Originally designed and sold by Dave Jones on the EEVBLOG, this derivative has several enhancements specifically for measuring varying currents on today's low power devices. Switch mode voltage regulators and the varying current draw of MCUs and RF chips require the determination of the current draw over time to calculate the total power consumption of a device. A storage oscilloscope is a perfect tool for this task and widely available. That's why the tinyCurrent features a BNC connector to reduce the picked-up noise while measuring with an and oscilloscope. Another problem is the high dynamics in power draw caused by the aforementioned reasons. This is addressed by the possibility to power the device from an external source with up to 5.5 V and bridge R7 using J6 to use the whole positive VDD as maximum positive output voltage. Both measures combined lead to almost 3 times higher dynamic range.
Min/Max Current per Range | |||
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Dynamic Range |
In general, the dynamic range in one direction can be determined by:VDD / 2 - 200 mV (security margin) = X mV . In case of VGND = VDD / 2 .
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@2.9V VDD (mean battery voltage over usage time) | |||
nA | ± 1250 nA (20 µV / nA burden voltage typical), contact resistance plays a role here. 10 µV due to the shunt resistor. | ||
µA | ± 1250 µA (10 µV / µA burden voltage) | ||
mA | ± 1250 mA (10 µV / mA burden voltage) | ||
@5.5V VDD (from external power source) | |||
nA | ± 2550 nA (20 µV / nA burden voltage typical), contact resistance plays a role here. 10 µV due to the shunt resistor. | ||
µA | ± 2550 µA (10 µV / µA burden voltage) | ||
mA | ± 2550 mA (10 µV / mA burden voltage) | ||
Resolution in nA Range |
1000 pA on a 3.5 digit DMM 100 pA on 4.5 digit DMM 10 pA 5.5 digit DMM |
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Accuracy, typical | |||
Output Offset Voltage, maximum | |||
Temperature Drift | |||
Noise | |||
THD | |||
Bandwidth (-3 dB) | 300 kHz | ||
Power Supply | CR2032 Lithium coin cell or max 5.5 V through connector J5 | ||
Battery Life | >50 hours (battery good LED ensures accurate measurement when LED is on). 2.65 V cutout voltage. | ||
Certifications | CE | ||
Materials | RoHS, REACH |
Similar to the original uCurrent Gold specs.
In order to keep the burden voltage low, this device has no OVERLOAD PROTECTION. That means NO FUSES. Care is required in using the unit to prevent damage.
All source files are available on Github. The schematics and PCB layout are in Altium Designer format.
Pick it up ready to use from the n-fuse website.
The circuit schematics of this project are made available under the CC-BY-SA license.
Open source hardware.
Data sheets, Altium libraries, 3D Models are subject to vendor specific licensing.