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121GW Multimeter

121GW Multimeter

Regular price $223.00 USD
Regular price Sale price $223.00 USD
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A unique, feature packed Multimeter which has been developed with electronics designers and hobbyists in mind.
This multimeter represents two years of collaboration between EEVblog and UEI.


Designed for professional electronics use, with unique features such as:

  • Bluetooth connectivity (multi-device capability)
  • Open Source Cross Platform application software (Android + Windows, and more soon)
  • 15V Diode Test Voltage (useful for Zeners + LED strings etc)
  • VA Power measurement
  • Low Burden™ voltage
  • Unique burden voltage display
  • Micro SD Card data logging + firmware updating

Other major features include:

  • Dual 50,000 count display with bargraph
  • 0.05% + 5 Basic DCV Accuracy
  • Auto-Hold measurement
  • 600V CAT-III with independent UL 61010 certification by ETL
  • Safe operation through HRC fuse + TVS + PTC + MOV + Diode Bridge protection

Hardware Features:

  • AD8436 >100KHz True RMS
  • 4 x AA battery powered with 500+ hr battery life
  • Compact design – 84 × 165 × 59 mm (W × L × H)
  • Hackable ST ARM Cortex M3 processor (S-LINK/V2 programmer interface inside)
  • Hycon HY3131 chipset
  • MAX4238 Low Offset Amplifier for current ranges
  • SD Card firmware update
  • Full Open Schematic available
  • 8ppm ADR3412 voltage reference

The meter is manufactured by UEI Test Instruments, a reputable US based designer and manufacturer of high quality test gear. The design work was primarily done by UEI, but with a great deal of design input and direction from Dave at the EEVBlog. The meter is manufactured in South Korea.

The meter comes with high quality Brymen silicone probes with 4mm banana plug attachments.

Additional information

Weight - 0.75 kg

Dimensions - 8 x 15 x 19cm

Matching Accesories:


121GW User Manual – 1st March 2020
Circuit Diagram


Note: When upgrading a multimeter the “.bin” file MUST be renamed “EEVBlog.bin”:

121GW Firmware 2.05  


EEVBlog2.02  EEVBlog2_00  EEVBlog1_58Beta  EEVBlog1_57  EEVBlog1_52  EEVBlog1_26  EEVBlog1_25  EEVBlog1_22  EEVBlog1_21  EEVBlog1_17  EEVBlog1_15  EEVBlog1_10  EEVBlog1_07  EEVBlog1_05  EEVBlog1_04  EEVBlog1_02  EEVBlog1_00

BLE Packet Format

Packet Format V1Packet Format V2


UEi’s Android App
Legacy Android App for older versions of Android
NOTE: Please use the 3rd Party Meteor App which is compatible with the latest Android version.
Windows App


The legacy android and iOS app source code is open source and available here: App GIT

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