Tag: multimeter teardown

Where is the ADC? RIGOL DM858 Teardown | Voltlog #486

Ever wondered what lies beneath the sleek exterior of the high-tech Rigol DM858 multimeter? In a recent teardown video, we took a deep dive into the inner workings of this precision instrument, uncovering the components that make it tick. Right off the bat, the teardown revealed the beautiful construction and assembly quality, with key areas like power supplies, connectivity, and a clever system-on-module design.

The power supply section was straightforward, with a USB-C input and a series of switchers to step down the voltage to the required levels. The real star of the show was the SODIMM module, housing an Allwinner A40i-H quad-core Cortex-A7 processor, RAM chips, flash memory, and a power management circuit.

This modular design offers several advantages, including cost savings, flexibility, and the ability to swap out components as needed. Moving on to the input section, we encountered a curious square PCB module housing the user-accessible fuse and input protection components like gas discharge tubes, Metal Oxide Varistors, and clamping devices.

Underneath a small shield, we found relays likely responsible for input switching and range selection. One of the most intriguing discoveries was the potential use of the microcontroller’s built-in ADC (Analog-to-Digital Converter) instead of a dedicated ADC chip. This design choice, if true, would be a clever solution for high sampling rates and accurate measurements.

However, not all mysteries were solved. We encountered a few unidentified components, leaving us scratching our heads. Can you help shed light on these enigmatic parts? Leave a comment below and join the discussion!

Excellent Build Quality Inside The UNI-T UT8805E | Voltlog #481

In the world of high-end multimeters, the UNI-T UT8805E stands tall with its impressive build quality and top-notch components. In a recent teardown video, we got an up-close look at what makes this professional-grade instrument tick. The teardown process revealed a meticulously designed interior, with high-quality parts sourced from reputable manufacturers like Analog Devices, Texas Instruments, and Maxim.

The mainboard boasts a large, matte green PCB panel with ample space, showcasing UNI-T’s commitment to quality. One of the standout features is the AD7122-2 24-bit, sigma-delta ADC from Analog Devices, capable of sampling up to 31kS/s, although UNI-T has wisely limited it to 5kS/s for improved noise performance.

Complementing the ADC is the MAX6225AESA+ 2.5V voltage reference with an impressive tempco of 1.5ppm per degree C and long-term stability of 20ppm/1000 hours at 25°C. The analog section is a true marvel, with a plethora of high-quality components like AD8622 rail-to-rail op-amps, OP72 op-amps, an AD637 RMS converter chip, ADG1209 multiplexers, and a MAX333A quad analog switch.

Input protection is top-notch, with surge arrestors, metal oxide varistors, and beefy film capacitors. At the heart of the instrument lies a TRION T20F256 FPGA, responsible for sampling data from the ADC and managing the auto-ranging features and measurements. The front panel boasts an STM32F407 Arm Cortex-M4 application processor, handling data from the FPGA/ADC and managing the display and keypad.

While UNI-T acknowledged a couple of issues in the initial review, they’ve assured that a newer revision has addressed these concerns. A fresh unit is on its way for further testing, so stay tuned for updates on this impressive multimeter’s performance.