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The K8 from Chinese manufacturer CZDANG is probably the strangest measuring instrument we have ever seen: a multimeter in the form of a wristwatch! Useful or useless? We tested it! |
Introduction to the K8 from CZDANG
What is CZDANG?
The brand name 'CZDANG' is used by 'Shenzhen ChenZhou Technology Co. Ltd.', founded in 2016, a Chinese company that is part of 'ChenZhou Island Industrial Co., Ltd.'. The company focuses on the design, development, production and sale of various products, including multimeters, soldering stations and hardware accessories. Its own (Chinese) website can be found at https://czdang.com. An internet search only reveals very cheap electronic measuring equipment, which is sold through well-known Chinese internet channels such as AliExpress, Temu, Alibaba and Banggood.
The K8 wrist multimeter
The K8 is an extremely small multimeter that, measuring 60 mm by 40 mm by 13 mm, is not much larger than a wristwatch. This is no coincidence, as this device is designed to be worn on the wrist. However, the K8 can only measure DC voltages, AC voltages and resistances. The meter is fully automatic, but you can also select the quantity to be measured manually.
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| The K8 multimeter from CZDANG and the wristband. (© 2025 Jos Verstraten) |
The instrument, which comes in a black case, can be clicked into a red wristband made of highly flexible plastic. However, the two spiral-wound measuring probes are permanently attached to the device and cannot be attached to the wristband. This means you have to insert them between the wristband and your wrist, which is not very convenient.
The fastening of the wristband is rather clumsy. At the end of the right half of the band, there is a small black pin that you have to push into one of the holes in the left half of the wristband. However, because the material of the band is so flexible, the pin slips out of the hole every few seconds and the multimeter falls to the floor. Very poorly designed!
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| This is how you should attach the K8 to your wrist. (© Banggood) |
Suppliers and prices
You can purchase the K8 through well-known online retailers such as AliExpress, Banggood, Temu, eBay, and Amazon. The lowest price we found on AliExpress is € 12.99 including shipping. At Banggood, it costs € 14.64.
Delivery of the K8 wrist worn multimeter
The meter is delivered in an attractive cardboard box. The box contains a plastic inlay, in which the K8 is neatly packaged. In addition to the meter, a USB charging cable and a miniature manual in English are included.
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| The multimeter is delivered neatly packaged. (© 2025 Jos Verstraten) |
The measuring probes
Everything about this multimeter is small, including the measuring probes. They are only 93 mm long and have a diameter of 7 mm. The highly flexible spiral cord is 18 cm long when at rest and can be extended to approximately 60 cm. The probes are equipped with a protective cap over the metal tip. This tip is only 9 mm long. It should be clear that these probes are absolutely not suitable for measuring high voltages!
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| The two measuring probes. (© 2025 Jos Verstraten) |
The display
The display is a monochrome LCD display with switchable lighting. Its dimensions are 35 mm by 27 mm. The digits are 16 mm high and therefore very easy to read. The lighting via a white LED above the display works excellently, allowing you to read the meter clearly even in complete darkness.
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| The symbols on the display. (© 2025 Jos Verstraten) |
Power supply
The K8 is powered by a small 3.7 V rechargeable battery with a capacity of 130 mAh. The charging cable is only 25 cm long and connects USB-C to USB-A. If you charge the device from a 5 Vdc power supply, the K8 will go into standby mode and you will not be able to use it for measurements. During charging, an LED mounted next to the USB-C connector will light up red. It will turn green when the battery is full.
The K8 manual
This is a miniature booklet measuring 50 mm by 65 mm with 14 pages. We have scanned it for you and saved it on our accounts at archive.org and Google Drive. You can download it via the link below:
The specifications of the K8
According to the manufacturer, the specifications are as follows:
- Display: monochrome LCD, 35 mm x 27 mm
- Number of measurements: three per second
- Number of counts: 1999 or 5999, depending on the measuring range
- Voltage ranges: 199.9 mV ~ 1.999 V ~ 5.999 V ~ 59.99 V ~ 300.0 V
- Voltage measurement accuracy: ±[0.5% + 3 counts]
- Voltage measurement input resistance: 10 MΩ
- Resistance ranges: 5999 Ω ~ 59.99 kΩ ~ 599.9 kΩ ~ 5.999 MΩ ~ 59.99 MΩ
- Resistance measurement accuracy: ±[1.2% + 3 counts] ~ ±[2.5% + 3 counts]
- Continuity measurement range: 50 Ω
- Data hold: yes
- Display illumination: yes
- Automatic measurement mode: yes
- Automatic switch-off: yes, after 15 minutes
- Power supply: 3.7 Vdc
- Battery capacity: 130 mAh
- Charging voltage: 5.0 Vdc
- Dimensions: 60 mm by 40 mm by 13 mm
- Weight (without wrist strap): 49 g
Operating the meter
This is extremely simple. Use the red button on the left to switch the meter on or off. The meter starts in 'Auto' mode. If you do not want this, you can switch to manual mode by briefly pressing the red button: Vdc ~ Vac ~ mVdc ~ mVac ~ Auto. Resistances and continuity can only be measured in 'Auto' mode. The 'Auto' function works for voltages greater than 600 mV. If you want to measure smaller voltages, you must always select the mV range manually.
Pressing the right blue button briefly activates 'Data hold' and freezes the reading. Pressing and holding this button switches the display lighting on and off.
The electronics in the K8 from CZDang
A circuit board measuring just 58 mm by 35 mm
All the electronics are contained on a tiny circuit board, as shown in the figure below. What immediately stands out is that all the resistors are miniature SMDs. In most multimeters, the resistors of the input voltage divider are large MELFs with a high breakdown voltage. This is definitely not the case with this meter. Resistors R8, R9 and R6 are slightly larger than the other resistors and probably form the input voltage divider. It is not without reason that the manual points out that 300 V is the absolute maximum voltage that can be applied to the inputs. And we consider that to be far too high a voltage for this little meter.
Furthermore, the protective components found in every multimeter at the input are completely absent. No PTCs, MOVs and/or VDRs to be seen! The only components that protect the circuit against overvoltage are the two transistors Q1 and Q2. In a meter with automatic range switching, these components are absolutely essential to protect the analogue inputs of the DMM chip against the input voltage.
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| The interior of the K8. (© 2025 Jos Verstraten) |
The two wires in the bottom right corner go to the battery that is attached to the back panel of the housing. The battery management system is located in the battery itself in the form of two small chips.
As you can see, the two wires from the measuring probes go to the circuit board without strain relief. The only thing that provides a little mechanical strength is a rubber grommet that is clamped into the housing and in which the two wires are clamped fairly tightly. We search in vain for a small slot milled between the two input paths, which is present on most DMM circuit boards to increase the creepage distance. As you can clearly see, the two wires from the measuring probes are soldered rather sloppily onto the circuit board, so that the clearance distance can also be small. None of this is as it should be!
The top of the DMM chip has been lasered, so the type number has disappeared. As a second chip, we discover a 15AL2437 that rings no bells with either Google or chatGPT.
Testing the K8 from CZDang
Introductory note
The following tables show values for voltage or resistance measurements in the left-hand column. These should not be considered absolute and should therefore not be used to assess the accuracy of the K8. This is why the symbol '≈' is used for these values. To assess accuracy, use the right-hand columns, which show comparative measurements taken with our much better laboratory equipment.
Incorrect specifications
The manual suggests that the K8 has two different count ranges: 1000 or 5999. However, this is incorrect. All measurements we have taken show that 1999 is the maximum number of counts.
Accuracy in DC voltage measurements
With the help of various power supplies and resistor dividers, we apply DC voltages between 1 mV and 300 V to the inputs of the meter. We check the actual value of the voltage with our Fluke 8842A reference meter. The results are summarised in the table below. As can be seen, the K8 performs quite well. At a voltage of 10 V, this multimeter deviates by only 40 mV, and at a voltage of 300 V by only 2.54 V, or less than 1%.
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| Accuracy when measuring DC voltages. (© 2025 Jos Verstraten) |
The input resistance when measuring DC voltages
According to the specifications, the input resistance for DC voltage measurements is 10 MΩ. To assess this parameter, we measure a stable DC voltage of approximately 10.0 V without and with a precise 1 MΩ resistor in series. Without this resistor, our K8 measures a voltage of 10.04 V, with the resistor a voltage of only 2.31 V. A voltage of 7.73 V therefore falls across the 1 MΩ resistor. From this data, the input resistance of the K8 can easily be derived as an astonishingly low 0.298 MΩ. This is nowhere near the 10 MΩ claimed!
Accuracy in 50 Hz AC voltage measurements
In most cases, you use the AC voltage function of a multimeter to measure 50 Hz voltages. That is why we tested this with a function generator for low voltages and with a variac for higher voltages at this frequency. Our ET3255 from EastTester is used as a reference meter.
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| Accuracy when measuring 50 Hz AC voltages. (© 2025 Jos Verstraten) |
Bandwidth when measuring alternating voltages
To test this, we feed our K8 and ET3255 with a sine wave signal of 1 Vrms at various frequencies. As shown in the table below, you can measure accurately from 10 Hz to approximately 2 kHz. This is fairly standard for inexpensive digital multimeters.
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| Bandwidth when measuring alternating voltages. (© 2025 Jos Verstraten) |
Accuracy in measuring resistances
For this test, we have a set of reference resistors with a tolerance of ±0.01% plus some less accurate ones. As a reference meter, we are of course using our Fluke 8842A. This meter uses a four-wire Kelvin probe, which is obviously not possible with the K8. The results are summarised in a clear table. You can see that the 1 Ω resistance is not recognised by the meter. However, from 10 Ω onwards, it works well and with satisfactory accuracy for such an inexpensive product.
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| Accuracy when measuring resistors. (© 2025 Jos Verstraten) |
Our conclusion about the K8 from CZDANG
We have never tested a product that is as ill-conceived as this K8 from CZDANG. What's more, the manual contains specifications that are incorrect.
As far as the electronics are concerned, the designers of this multimeter have not included any of the standard features to protect their product and its user from excessive input voltages. A first-year electronics student who takes a moment to study the construction of multimeters could do better! Our urgent advice is therefore: only use this K8 for measuring resistances and low DC and AC voltages!
As for the wristband, both the idea and the execution are clumsy and impractical. Perhaps the K8 would have been useful for some measurements in a better-designed wristband if the designers had connected the measuring leads to the device by means of a connector. But now you have to carry those two awkward, cumbersome measuring probes and cables around with you, which really makes no sense at all.
Is the CZDANG K8 complete useless? Because it measures resistors quite accurately and takes up little space, we have replaced the two measuring probes with miniature clips with crocodile jaws and use the device to quickly select a resistor from a pile when soldering electronic kits. Due to our poor eyesight, this is faster than deciphering those very thin coloured lines.
If you work with SMDs a lot, you can solder measuring tweezers to the wires and quickly look up the value of SMD resistors with a device that takes up only a very modest amount of space on your workbench.
K8 wrist worn multimeter
