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For just € 35.00, Chinese manufacturer ZOYI is launching a multimeter with 25000 counts and a specified accuracy for DC voltage of ±[0.05% + 3]. A device that is definitely worth testing! |
Introducing the ZT-225 from ZOYI
Who is ZOYI?
Shenzhen ZOTEK Instruments Co., Ltd. was founded in 2015 by Li Hong and his son Li Xin and is active in the development of digital and clamp multimeters, infrared thermometers, coating thickness meters, voltage detectors and wall socket testers. In countries where the name ZOYI was already registered as a brand name, the name ZOTEK is used. Li Hong is known in China as the man who introduced the first Chinese digital multimeter, which at the time used the well-known ICM7106 chip.
What is so special about the ZT-225?
The fact that this meter has a readout of up to 25000 counts and costs less than forty euros! This means you can measure a supply voltage of, for example, 12 V with a resolution of 1 mV. Please note: this does not mean that the ZT-225 is accurate to 1 mV. That is a completely different story, which we will return to later in this review/test.
Those 25000 counts do not apply when measuring capacitors, where the readout is limited to 09999.
A second special feature is that this multimeter has all the extras that a good modern multimeter should have:
- Display of minimum and maximum values within a measurement cycle.
- Relative function, ideal for measuring small resistances.
- Hold function, which 'freezes' the last measured value on the screen.
- Both automatic and manual selection of the measurement range.
- Thirteen measurement functions, adjustable via the rotary switch.
- Can measure AC+DC.
- Measures the RMS value of AC voltages.
- Three measurements per second.
- Two digital and one analogue scale.
- Minimum measurement range of 25.000 mV, both DC and AC.
- Accuracy for DC voltage measurements of ±[0.05% + 3].
- Current range up to 20.000 A (10 seconds maximum).
- Continuity measurement up to 50 Ω.
- Accuracy for resistance measurements of ±[0.2% + 3].
- Two built-in fuses for the current measurement ranges.
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| The appearance of the ZT-225 from ZOYI. (© ZOYI) |
Note
We have also seen this multimeter offered online as Aneng SZ20, KUSAM-MECO KM-405 and NEWRUIKE XCRK61E, albeit in slightly different colours, but for roughly the same price. The main difference, however, is that the SZ20 appears to be much less accurate. For DC voltages, for example, only ±[0.2% + 10] is specified instead of the ±[0.05% + 3] for the ZT-225. All other accuracy specifications are also much worse.
Suppliers and prices
You can purchase the ZT-225 through the well-known online channels such as AliExpress, eBay and Amazon. The lowest price we found on AliExpress is € 34.99 including shipping.
Scope of delivery
The ZT-225 comes in a beautifully printed gift box with the following contents:
- The meter itself.
- Two insulated test probes.
- A thermocouple probe.
- A 28-page manual in A6 format.
- A soft plastic case that fits everything.
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| The scope of delivery of the ZT-225. (© AliExpress) |
The power supply
The ZT-225 is powered by three standard 1.5 V AA batteries. However, these are not included.
The test probes
It seems as if all Chinese multimeter manufacturers purchase their probes from the same factory. The ZT-225 also comes with a set of these test probes, which are of good quality. The test probes have a needle-shaped tip, which you can insulate with covers if necessary. The other end is equipped with safety banana plugs. If you are not using the probes, you can seal these banana plugs with caps to prevent dust or moisture from settling on the metal parts. The two approximately one meter long cables are very flexible, thanks to PVC or silicone imitations as insulation and the very thin central core.
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| The test probes. (© AliExpress) |
The thermocouple probe
This is a rather cheap-looking measuring lead with a type K thermocouple at one end in the tip of a hollow stainless steel rod and two extremely rudimentary banana plugs at the other end. This could have been done much better!
The banana plugs fit into the multimeter's sockets with great difficulty, and when you pull these banana plugs out again, you have to use quite a bit of force, which means that you risk damaging the multimeter's sockets.
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| The thermocouple probe. (© AliExpress) |
The ZT-225 manual
This is a very well-designed 28-page booklet in A6 format, which describes all the features of this multimeter in clear English. We have scanned this booklet and saved it to our account at archive.org, from where you can download it:
The appearance of the ZT-225
In the illustration below, we have collected the three views of this multimeter. The meter is large, measuring 180 mm x 90 mm x 50 mm, and weighs 326 g with batteries. The old-fashioned monochrome LCD display measures 61 mm by 44 mm, on which the digits of the primary reading are displayed at a height of 21 mm. In the upper right corner, you will find the secondary reading with digits 6 mm high. For most measurements, the temperature in the meter appears here, which is apparently many degrees higher than the room temperature. A rather useless measurement! For AC voltage measurements, the frequency of the signal is displayed. If you measure AC+DC, the primary display shows the DC voltage and the secondary display shows the AC voltage superimposed on that DC voltage. For frequency measurements, the duty cycle appears on the secondary display.
Below the primary display, you will see the third scale, analogue, which consists of sixty segments. All displays are refreshed three times per second.
As an extra feature, the ZT-225 has a red LED between the two current input sockets that lights up when you switch the meter to one of the three current measurement ranges.
On the back of the housing, you will see the fold-out backrest, under which the battery compartment is hidden.
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| Three views of the ZT-225. (© 2025 Jos Verstraten) |
The control buttons
The large round switch has fifteen settings:
- OFF
- Vac/Hz/%
- Vdc
- V/Vac+dc
- mVac/mVdc/Hz/%
- Resistance
- Diode/Continuity
- NCV
- Capacitance
- Hz/%
- °C/°F
- Adc/Aac/Hz/%
- mAdc/mAac/Hz/%
- μAdc/μAac/Hz/%
- OFF
Where there is a '/' symbol, you can switch from one measurement function to another using the 'SEL/REL' push button. The '%' symbol refers to the duty cycle measurement function.
Above this large function button are four push buttons:
- SEL/REL:
Press this button briefly to switch between measurement functions at the relevant positions of the rotary knob. Press and hold this button for more than two seconds to switch to 'REL' mode. This stores the current measurement value in the memory and subtracts it from all subsequent measurements. This is ideal for compensating for the resistance of the measuring leads when measuring very low resistance values. Press and hold this button for more than two seconds to exit this mode. - RANGE:
Pressing this button exits automatic range switching and allows you to set the measuring range manually. Press and hold this button for more than two seconds to switch back to automatic mode. - MAX/MIN:
Switches between displaying the maximum and minimum measurement values in the current measurement cycle. Press and hold this button for more than two seconds to return to the current measurement value in the primary display. - HOLD/☼:
Press briefly to freeze the current measurement value on the screen. Press again briefly to exit this mode. Press for longer than two seconds to switch the display backlight on or off.
An unusual error in the software
Like all modern multimeters, the ZT-225 has a white LED on the top of the housing that can be used to illuminate the measurement site. However, this LED turns on automatically when you switch on the display backlight and cannot be controlled separately.
Automatic switch-off
The ZT-225 switches itself off after approximately fifteen minutes. If you do not want this to happen, you must hold down the “SEL/REL” push button while switching on the meter with the rotary switch. You will hear four short beeps to indicate that this function has been deactivated.
The specifications of the ZT-225
According to the manufacturer, this multimeter meets the following specifications:
- Display: LCD monochrome screen
- Number of counts: 25000 or 09999
- Measurement method: A/D conversion with double integration
- Measurement range switching: automatic or manual
- Sampling rate: 3 times per second
- Measurement ranges mV DC voltage: 25.000 mV ~ 250.00 mV
- Accuracy mV DC voltage: ±[0.05% + 3 counts]
- Measurement ranges V DC voltage: 2.5000 V ~ 25.000 V ~ 250.00 V ~ 1000.0 V
- Accuracy V DC voltage: ±[0.05% + 3 counts]
- Measuring ranges mV AC voltage: 25.000 mV ~ 250.00 mV
- Accuracy mV AC voltage: ±[0.3% + 3 counts]
- Measurement ranges V AC voltage: 2.5000 V ~ 25.000 V ~ 250.00 V ~ 1000.0 V
- Accuracy V AC voltage: ±[0.3% + 3 counts]
- Measurement ranges DC current: 250.00 μA ~ 2500.0 μA ~ 25.000 mA
- Measurement ranges DC current: 250.00 mA ~ 2.5000 A ~ 20.000 A
- Accuracy DC current: ±[0.5% + 3 counts]
- Measurement ranges AC current: 250.00 μA ~ 2500.0 μA ~ 25,000 mA
- Measurement ranges AC current: 250.00 mA ~ 2.5000 A ~ 20.000 A
- Accuracy AC current: ±[0.8% + 3 counts]
- Measurement ranges resistance: 250.00 Ω ~ 2.5000 kΩ ~ 25.000 kΩ
- Measurement ranges resistance: 250.00 kΩ ~ 2.5000 MΩ ~ 25.00 MΩ ~ 250.0 MΩ
- Accuracy resistance: ±[0.2% + 3 counts] ~ ±[5.0% + 5 counts]
- Measurement ranges capacitance: 9.999 nF ~ 99.99 nF ~ 999.9 nF ~ 9.999 μF
- Measurement ranges capacitance: 99.99 μF ~ 999.9 μF ~ 9.999 mF ~ 99.99 mF
- Accuracy capacitance: ±[2.0% + 5 counts] ~ ±[5.0% + 20 counts]
- Measurement ranges Frequency: 250.00 Hz ~ 2.5000 kHz ~ 25.000 kHz
- Measurement ranges Frequency: 250.00 kHz ~ 2.5000 MHz ~ 10.000 MHz
- Accuracy frequency: ±[0.1% + 2 counts]
- Measurement range duty cycle: 1% to 99%
- Accuracy duty cycle: ±[0.1% + 2 counts]
- Measurement range temperature: -20 °C to +1000 °C
- Accuracy temperature: ±[3.0% + 5 counts]
- Diode measurements: yes, up to 3.2 V
- Low resistance buzzer measurement: yes, up to 50 Ω
- HOLD function: yes
- MIN/MAX measurements: yes
- REL measurements: yes
- NCV measurements: yes
- Flashlight: yes
- Automatic shut-off: yes
- Display lighting: yes
- Low battery indicator: yes
- Power supply: three 1.5 V AA batteries
- Dimensions: 180 mm x 90 mm x 50 mm
- Weight: approx. 326 g
The electronics in the ZT-225
Super integration
To open the meter, you first have to wriggle it out of its plastic protective cover, which takes some effort. Then you can remove four screws and pull the two shells of the housing apart.
You also have to open the meter if you accidentally blow one of the fuses.
The circuit board completely fills the front shell of the housing. The photo below shows that highly integrated ICs are used nowadays. The circuit board contains only three chips:
- The square chip:
This is probably the 'DMM controller' that contains all the electronics for measuring all the quantities that you can measure with the ZT-225. The type number has been made illegible. According to some sources on the internet, this could be a DTM0660L. However, the specifications of this chip show that it outputs a maximum number of counts of 9999. According to other sources, ZOYI uses a Hycon HY12P66 or HY12P65. - ET6621S:
This is the chip in the lower left corner of the PCB. It is a very popular LCD driver from Etek Microelectronics. - K24C08:
The small IC between the two chips already discussed, a flash memory in which the calibration data of the DMM controller is stored.
On the right side of the PCB you can see the two sand-filled fuses and a number of safety devices. The way they are mounted on the PCB makes a rather sloppy impression. The blue components are undoubtedly MOVs and the two green components are PTCs. The five diodes D5 to D9, arranged in an H-shape, are undoubtedly also part of the meter's protection. Note that a number of slots have been milled into the PCB around the inputs. These provide extra insulation between the tracks on the PCB and increase the creepage distance of the design.
Between the two upper red banana sockets, you can see a metal bracket. This is, of course, the shunt resistor for the 20 A measuring range. Although it is clearly stated that you may measure such currents for a maximum of ten seconds, you and we know that such warnings are often ignored in practice. The layout of that part of the PCB gives us the creeps... Far too many components that can become hot are placed far too close together!
One argument in favour of the design of this meter is that eight resistors are implemented as MELF, which are much more reliable than the mini chip resistors that we encounter in many cheap Chinese multimeters.
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| The interior of the ZT-225. (© 2025 Jos Verstraten) |
Testing the ZOYI ZT-225
Introductory note
The following tables show values for voltage, current, resistance or capacitance in the left-hand column. These should not be considered absolute and should therefore not be used to assess the accuracy of the ZT-225. This is why the symbol “≈” is used for these values. To assess accuracy, use the right-hand columns with comparative measurements taken with our much better laboratory equipment.
Note on accuracy
A specified accuracy of ±[0.05% + 3 counts] for DC voltage is... very accurate! Suppose you measure a voltage of exactly 10.000 V on the 25.000 V range. The meter may then deviate by a maximum of ±8 mV, so that the reading must be between 9.992 V and 10.008 V. Testing the accuracy of the ZT-225 therefore means reliably measuring differences of a few millivolts!
To test this properly, you need extremely expensive laboratory measuring equipment. We don't have that; our most accurate instrument is a Fluke 8842A. This is a highly accurate multimeter with a maximum deviation when measuring DC voltage of ±[0.006% + 3 counts], two years after calibration. Although our multimeter was calibrated four years ago, experience shows that the error does not change much. In any case, that is more than accurate enough to assess the ±[0.05% + 3 counts] of the ZT-225. In the tables below, we therefore consider the measurements with our 8842A to be correct (100%) and calculate the percentage error on the measurements with the ZT-225 relative to that value.
Accuracy when measuring DC voltages
We use various DC voltage sources and resistive dividers to cover a range from 10 mV to 950 V. As you can see from the table below, the ZT-225 measures DC voltages with extreme accuracy. The average percentage deviation from the Fluke measurements over the entire range is only 0.068%. The system that automatically selects the correct measuring range works extremely quickly.
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| Accuracy when measuring DC voltages. (© 2025 Jos Verstraten) |
The input resistance when measuring DC voltages
To assess this parameter, we measure a stable DC voltage of approximately 30.0 V without and with a precise 1 MΩ resistor in series. Without this resistor, the ZT-225 measures a voltage of 29.95 V, with the resistor a voltage of 27.22 V. A voltage of 2.73 V therefore falls across the 1 MΩ resistor. From this data, the input resistance of the ZT-225 can easily be derived: 9.97 MΩ.
Accuracy when measuring DC currents
We formed a series circuit consisting of a DC power supply with digitally adjustable current, the ZT-225, and our reference meter, the 8842A. The measurement results are summarised in the table below. You will undoubtedly agree with us that there is little to criticise here! The average deviation from the Fluke is only 0.20%. According to the specifications, this value is ±[0.5% + 3 counts].
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| Accuracy when measuring direct currents. (© 2025 Jos Verstraten) |
The burden voltage when measuring DC currents
The burden voltage is the voltage across the meter when you measure a current. The smaller this voltage, the less influence the measurement of a current has on the circuit in which you are measuring. At a current of 5 A, a voltage of 153 mV falls across the inputs of the meter. In the mA range of 250.00 mA, a full-scale measurement results in a voltage of 282 mV.
Accuracy when 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 naturally use our Fluke 8842A. This meter uses a four-wire Kelvin probe, which is not possible with the ZT-225. When measuring very low resistances, the resistance of the measuring cables and the contact resistance of the input sockets obviously play a major role. Fortunately, these can be compensated for in the ZT-225 with the 'REL' function. The results are summarised in a table. With this measurement function, too, the deviations are smaller than the specifications promise.
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| Accuracy when measuring resistances. (© 2025 Jos Verstraten) |
Accuracy when measuring 50 Hz AC voltages
We use our DG1022 function generator and a variac to generate 50 Hz sinusoidal voltages between 5 mV and 250 V. At AC voltages in the mV range, there are some deviations between the readings on the ZT-225 and the ET3255 from Easttester, which we use as a reference meter. However, all larger 50 Hz AC voltages are measured with good accuracy.
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| Accuracy when measuring 50 Hz AC voltages. (© 2025 Jos Verstraten) |
Bandwidth when measuring AC voltages
To test this, we feed the ZT-225 and the 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.
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| The bandwidth when measuring AC voltages. (© 2025 Jos Verstraten) |
Accuracy when measuring capacitors
Thanks to a set of five accurate capacitors with a tolerance of ±1% and a pair of reference capacitors with a tolerance of only ±0.1% and ±0.05%, we can accurately map the performance of the ZT-225 when measuring such components. Above 1 µF, we measure regular electrolytic capacitors from our stock. As a reference meter, we use the ET4401 from EastTester with an accuracy of ±0.2% for non-electrolytic capacitors. This meter measures using a four-wire technique, something that is not possible with the ZT-225. This causes additional measurement errors, especially when measuring very small and very large capacitors (electrolytic capacitors!), as is clearly shown in the table below. This is a problem that all multimeters have when measuring capacitors. From 1 nF to 1 μF, the measurement results are excellent again.
The speed at which electrolytic capacitors are measured is interesting. With the 100 μF electrolytic capacitor, it takes about four seconds before the reading is stable, while with the 10 mF electrolytic capacitor, the meter takes about seven seconds. With these values, the ZT-225 is in the middle of the peloton. We have tested multimeters that are faster, but also ones that measure electrolytic capacitors at an excruciatingly slow pace.
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| Accuracy when measuring capacitors. (© 2025 Jos Verstraten) |
Sensitivity when measuring frequencies
When measuring frequencies, the sensitivity of the meter is particularly interesting. We therefore measure the rms voltage at which the ZT-225 displays the frequency of the signal in a stable manner. Above 1 MHz, the sensitivity decreases rapidly.
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Sensitivity when measuring frequencies. (© 2025 Jos Verstraten) |
Accuracy when measuring temperatures
This accuracy is not so easy to measure! We have developed the following measurement setup. We drill a 1.5 cm deep hole with a diameter of 4 mm in the side of a large aluminium heatsink. We fill this hole with heat-conducting paste and push the tip of the thermocouple supplied with the ZT-225 into that hole. We use our calibrated Fluke 52 meter as a reference. We also push the two thermocouples from this meter into the hole. The three thermocouples are therefore at the same temperature. We clamp a 100 W wire-wound resistor onto the heatsink and connect it to an adjustable power supply. We cool the heatsink with a can of 'liquid air' to below freezing point. We switch on the power supply so that the heatsink slowly heats up. When the Fluke indicates a multiple of ten, we quickly read the ZT-225 as well. We record the readings from both meters in the table below.
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| Accuracy whwn measuring temperatures. (© 2025 Jos Verstraten) |
Our opinion of the ZT-225 from ZOYI
We are quite impressed with this multimeter. You will agree with us that this instrument measures all the quantities offered very accurately. And that for a device that costs less than forty euros!
One point of criticism is the very limited bandwidth when measuring AC voltages. Admittedly, all cheap multimeters perform poorly in this area, but a bandwidth of only 2 kHz is very limited.
It is a pity that the designers did not pay more attention to the way the input protections are placed on the PCB. That could have been better!
ZOYI ZT-225 multimeter
