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Priced at around fifty euros, the QLS3600S-10M is an affordable function generator for hobbyists, offering a wide range of features and surprisingly good signal quality. |
Introducing the QLS3600S-10M from Qletek
The QLS3600S-10M function generator
This device is part of the QLS3600 family, comprising five virtually identical generators that differ only in their frequency range: from 5 MHz to 30 MHz. For this test, we purchased a QLS3600S-10M which, with a frequency range of 10 MHz for all signal waveforms, strikes a good balance between a hobbyist's requirements and the price. This function generator is supplied without a casing, which undoubtedly contributes to its affordable price of around fifty euros. The two circuit boards are mounted in a sandwich construction between the front and rear panels. The three BNC inputs and outputs are located on the right-hand side, whilst the left-hand side houses the connectors for the power supply and the external trigger or VCO signals.
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| The appearance of the QLS3600S-10M. (© Banggood) |
Key features of the QLS3600S-10M
- Powered by 5.0 Vdc, so it can be used off-mains via a power bank.
- 2.5 inch colour display.
- Full control via push buttons and a single rotary knob.
- Frequency range for all signals from 0.01 Hz to 10.00 MHz.
- Eighteen pre-programmed signal waveforms.
- Fifteen user-definable signal waveforms via a PC.
- Sixteen memory locations for storing settings.
- Precise numerical setting of frequency, amplitude, offset and duty cycle.
- In addition to generating constant signal waveforms, the following functions are available: burst, sweep, VCO and pulse.
- AM, FM and pulse-width modulation possible via the VCO function.
- Built-in frequency, period and pulse counter.
- Internal and external triggering possible.
- TTL output provided.
- Control via USB from a PC.
The manufacturer of the QLS3600S-10M
This must apparently remain a secret, as it is not mentioned on the packaging, in the manual or on the device itself. According to various AI sources, the manufacturer is the Chinese electronics company 'Qingdao Qletek Electronic Co., Ltd.', abbreviated to Qletek. This generator is supplied by the manufacturer to major resellers as a unbranded OEM unit and is marketed under various made-up names.
Suppliers and price
All the well-known Chinese resellers, such as Banggood and AliExpress, sell the device, but eBay and Amazon also offer it at ridiculously high prices. On AliExpress, it costs € 53.69, and on Banggood, € 51.81. When ordering, make sure you select the correct version (5 MHz, 10 MHz, 15 MHz, 20 MHz or 30 MHz).
The packaging of the QLS3600S-10M
The unit is supplied in a neat cardboard box measuring 25.0 cm by 8.5 cm by 11.0 cm. The generator is securely held in place by two polystyrene supports, ensuring it is well protected against damage to the box during transport.
What's included with the QLS3600S-10M
Inside the box you will find:
- The QLS3600S-10M itself.
- A 5.0 Vdc ~ 2 A mains power supply.
- A BNC to BNC cable.
- A BNC to alligator clip cable.
- A USB-A to micro-USB cable.
- An eight-page user manual in English.
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| What's inside the QLS3600S-10M packaging. (© Amazon) |
The appearance of the QLS3600S-10M
The photograph below shows a front view of this unit. The front panel measures 17.2 cm by 7.1 cm. The 48 mm by 37 mm display shows only the essential data relating to the generated signal. It is a pity that the bottom window of the frequency counter is always visible, even when you are not using this function. Next to the display are the five function keys 'F1' to 'F5', which allow you to make selections on the display. Using the '◄' and '►' keys, you can select a parameter whose value you wish to change. You do this by turning the large round rotary knob. Finally, there are four other push-buttons, the functions of which are explained in the section 'Working with the QLS3600S-10M'.
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| The front view of the QLS3600S-10M. (© 2026 Jos Verstraten) |
On the left-hand side, which you can see in detail in the photo below, are the following, from left to right:
- The green terminal block for connecting the trigger or VCO signal.
- The micro-USB connector for connecting the generator to your PC.
- A standard power supply connector.
- A miniature ON/OFF slide switch.
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| The left-hand side view of the QLS3600S-10M. (© 2026 Jos Verstraten) |
The user guide
We have uploaded the user guide to our private cloud on Google Drive, and you can download it via the link below:
General specifications of the QLS3600S-10M
- Supply voltage: 5.0 Vdc
- Supply current: 2.0 A max.
- Amplitude resolution: 10 bit (1,024 voltage levels)
- Period resolution: 1,024 samples per period
- Dimensions: 187 mm x 71 mm x 24 mm
- Weight: 220 g
- Number of memory locations: 15
- Interface: USB to serial interface, 57,600 bps
Signal specifications
- Frequency range for all signals: 0.01 Hz to 10,000,000.00 MHz
- Frequency setting resolution: 0.01 Hz
- Frequency setting accuracy: ±[8 × 10⁻⁶]
- Frequency stability: ± [5 × 10⁻⁶]
- Number of predefined waveforms: 18
- Number of user-definable waveforms: 15
- Amplitude: 10 mV to 20.00 V (up to 5 MHz)
- Amplitude: 10 mV to 10.50 V (above 5 MHz)
- Amplitude setting resolution: 0.01 V
- Amplitude stability: ±0.5 %
- Amplitude setting accuracy: ±[1 % + 10 mV]
- Offset setting range: -10 V to +12 V
- Duty cycle setting range: 0.1 % to 99.9 %
- Harmonic distortion on sine wave: <0.8 % (20 Hz to 20 kHz)
- Rise/fall time of square wave signal: 20 ns max.
- Output impedance: 50 Ω ±10 %
Burst specifications
- Triggering: manual or external
- Number of periods: 1 ~ 999,999
Pulse output specifications
- Period: 20 ns ~ 99 s
- Pulse width: 20 ns ~ 99 s
Sweep output specifications
- Sweep mode: linear or logarithmic
- Sweep direction: up, down, back and forth
- Sweep time: 100 ms to 999.9 s
- Frequency range: all frequencies
VCO output specifications
- External voltage: 0 V to 5.0 V
- Controllable parameter: amplitude, frequency or duty cycle
Frequency/period/pulse counter specifications
- Frequency range: 0.01 Hz to 100.00 MHz
- Period range: 20 s max
- Period measurement resolution: 0.01 μs
- Pulse range: 4,294,967,295 max.
- Input voltage: 0.5 Vp-p min, 10.0 Vp-p max.
Signal waveforms
As well as the familiar sine, square and triangle waveforms, the QLS3600S-10M provides the fifteen signal waveforms listed below, although you are unlikely to use them very often, if at all.
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| The non-standard signal waveforms. (© Banggood) |
The electronics in the QLS3600S-10M
Sandwich construction
The two circuit boards are assembled together with the plexiglass front and rear panels using a number of threaded metal spacer sleeves. The device is therefore easy to dismantle. As shown in the photograph below, all the electronics are housed on a single circuit board. This is connected via a ribbon cable to the second board, which only contains the push-buttons, the rotary encoder and the display.
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| The main circuit board of the QLS3600S-10M. (© 2026 Jos Verstraten) |
The ICs used
On this circuit board you will find ten ICs, the type codes of which – quite unusually for Chinese designs – have not been lasered off.
- W25Q16JVSSIQ:
This Winbond chip is a 16 megabit serial NOR flash memory chip. It is likely used to store the firmware and the data tables describing the signal waveforms. - LCMXO2:
This belongs to a series of programmable logic devices (PLDs) from Lattice, known as the MachXO2 family. - 74HC14D:
This 74HC14D is a hex inverting Schmitt trigger. - DAC900E:
The DAC900E is a high-speed, 10 bit digital-to-analogue converter (DAC) from Texas Instruments (originally developed by Burr-Brown). It belongs to the SpeedPlus family of high-performance converters. This type of IC is specifically designed to convert digital data streams at very high speeds into extremely accurate analogue signals. It is clear that this chip is used to generate the analogue waveforms from the data tables stored in the device's memory. The maximum sampling rate is 165 MSa/s. - STM32F103:
The STM32F103 is one of the most popular 32 bit microcontrollers in the world, developed by STMicroelectronics. It is the standard controller for virtually all low-cost Chinese measuring equipment. - CH340G:
A popular USB-to-serial adapter chip (UART), developed by the Chinese company WCH (Jiangsu Qinheng Co.). - APM4953:
Although the APM4953 from Anpec Electronics is housed in an IC package, it is a dual P-channel enhancement-mode MOSFET. In this device, these MOSFETs are likely used in the DC/DC converters that convert the 5.0 V supply voltage into higher negative and positive supply voltages. - XL6008:
The XL6008 is a DC/DC converter manufactured by XLSEMI. It is a switching regulator primarily designed to efficiently step up voltages and/or reverse the polarity. - 78M05:
The well-known +5.0 V regulator. - 79M05:
The equally well-known -5.0 V stabiliser
Working with the QLS3600S-10M
Preliminary note
As with virtually all low-cost function generators, the signal magnitude is displayed and set as 'Amplitude'. This refers to what is known in Dutch as the 'peak-to-peak' value of the signal. We are accustomed to working with root-mean-square (RMS) values, particularly when a sinusoidal signal is being generated. The conversion factor from the peak-to-peak value to the RMS value is 0.3536. Conversely, the conversion factor is 2.8284.
So, if you need a sinusoidal signal of 1.0 Vrms, you must set the QLS3600S-10M to an amplitude of 2.83 V.
Generating constant signals
Once the unit has been switched on using the toggle switch, the QLS3600S-10M immediately enters the mode in which a sine wave with a frequency of 10 kHz and an amplitude of 10.00 V is generated. The figure below shows the data that appears on the display. The bottom window is superfluous in this mode, as it displays the frequency counter data.
Setting up the function generator is very simple and straightforward. Use the five function keys 'F1' to 'F5' to select the following settings:
- 'F1' (WAVE): the signal waveform.
- 'F2' (FREQ): the frequency.
- 'F3' (AMPL): the peak-to-peak value of the signal.
- 'F4' (OFFS): the value of the offset voltage.
- 'F5' (DUTY): the value of the signal's duty cycle.
The 'DUTY' setting only affects the output signal if you select 'Square' under 'WAVE'.
To set the desired waveform, press 'F1' and then use the large rotary knob to select the desired waveform. The type of waveform is shown on the display both graphically and as text.
The four parameters are set as follows. First, press the relevant function key and use the '◄' and '►' keys to select the digit you wish to change. This will be highlighted in red; use the large rotary knob to adjust the value.
Once you have set all the signal parameters, press the 'Out' button and the signal will appear at the 'OUT' connector.
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| The display when generating constant signals. (© Qletek) |
The modulation functions
Selecting with 'Function' and 'Mode'
As mentioned earlier, you can modulate the set signal in various ways:
- 'Burst Out'.
- 'Sweep Out'.
- 'VCO Out'.
- 'Pulse Out'.
You can select these four functions by first pressing the 'Function' button and then pressing the 'Mode' button once or several times.
To exit any of these functions, simply press the 'F1' (ESC) button briefly.
The 'Burst Out' function
This function allows you to generate a 'burst', comprising a configurable number of periods of the set signal. The menu for configuring this function is shown in the figure below.
- 'F2' (PULSE):
This sets the number of periods in the burst. You can enter a number between 1 and 999,999. - 'F3' (MODE):
'Manual' or 'External'. In the first case, you generate a single burst by pressing the 'Out” button. In the second case, the generator produces a burst upon a rising edge of a TTL-compatible signal at the trigger input on the left-hand side. - 'F4' (ON):
You must press this button to activate the burst function. This is really only relevant if you are using external triggering. After pressing this button, the first burst will appear on the first rising edge of the trigger signal. - 'F5' (OFF):
This switches the function off.
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| The 'Burst Out' function menu. (© 2026 Jos Verstraten) |
The 'Sweep Out' function
This function also has its own menu; see the image below. As there are five parameters to set here, assigning a single function button to a single parameter no longer works; you must therefore use the 'F2' (▲) and 'F3' (▼) function keys to select one of the parameters.
- 'Start':
The start frequency of the sweep. - 'End':
The end frequency of the sweep. - 'Mode':
Choice between linear or logarithmic sweep. - 'Time':
The duration of a single sweep. - 'Dection':
A minor typographical error – this should, of course, be 'Direction'! The sweep can be set to run from low to high (Forward), from high to low (Reverse) or back and forth (Reciprocat).
You can, of course, start or stop a sweep using 'F4' (STAR) and 'F5' (STOP).
It should be noted that you can sweep across the entire frequency range of the QLS3600S-10M! The current output frequency appears after 'Freq' on the display.
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| The 'Sweep Out' function menu. (© 2026 Jos Verstraten) |
The 'VCO Out' function
This is a very comprehensive function. After all, you can have an external signal control the frequency, amplitude or duty cycle. This means that, using this function, you can apply amplitude, frequency or pulse-width modulation to the signal! The menu is shown in the figure below.
Once again, you must use the 'F2' (▲) and 'F3' (▼) function keys to select one of the five adjustable parameters.
- 'Mode':
Select whether you want the amplitude, frequency or duty cycle to be modulated by the external signal. - 'Start':
Select the start value of the selected parameter. - 'End':
Select the end value of the selected parameter. - 'Ref Start':
Set the control voltage corresponding to the start value of the selected parameter. To do this, apply a DC voltage equal to the desired voltage to the external input and press 'SET'. - 'Ref End':
Set the control voltage corresponding to the end value of the selected variable. To do this, apply a DC voltage equal to the desired voltage to the external input and press 'SET'. - 'Input':
Displays the current value of the control voltage. - 'Out':
Displays the value of the controlled variable corresponding to this control voltage.
Press 'F5' (SART/STOP) to start or stop the generation of the VCO voltage.
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| The 'VCO Out' function menu. (© 2026 Jos Verstraten) |
The 'Pulse Out' function
As can be seen from the figure below, the programmers have made a minor linguistic error here too. It says 'Pluse Out' instead of 'Pulse Out'! For this function as well, you must use the function keys 'F2' (▲) and 'F3' (▼) to select one of the four adjustable parameters. These are self-explanatory:
- 'Width': the width of the pulse.
- 'Period': the period of the signal.
- 'AMPL': the amplitude of the pulse.
- 'OFFS': any offset voltage applied to the pulse.
Use 'F4' (ON) and 'F5' (OFF) to switch the output on or off.
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| The 'Pulse Out' function menu. (© 2026 Jos Verstraten) |
The frequency/period/pulse counter
The frequency/period counter
You activate this function by pressing the 'Test' button in the main menu. A rather unusual label for such a function! Why not label this button 'Count'? Press 'F5' to switch between measuring the frequency (FREQ) or the period (CYLE) of a signal. Using the 'F4' (GATE) push button and the rotary knob, you can set the counter's gate time to 0.01 s, 0.1 s, 1.0 s or 10.0 s. The longer the gate time, the higher the measurement resolution! Press 'F3' (◄) to start the measurement, and 'F2' (ǀǀ) to stop it.
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| The frequency/period counter menu. (© 2026 Jos Verstraten) |
The pulse counter
By clicking the 'Mode' button on the frequency/period counter, the QLS3600S-10M changes to a pulse counter with a range of up to 4,294,967,295 pulses. Press 'F3' (◄) to start the measurement, and 'F2' (ǀǀ) to stop it. Press 'F4' (CLR) to reset the counter to zero.
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| The pulse counter menu. (© 2026 Jos Verstraten) |
The 'System Setting'
Finally, there is the menu where, amongst other things, you can save and recall sixteen settings in the internal memory: the 'System Setting'. You open this menu by pressing and holding the 'Mode' button for more than a second. The figure below shows what this menu has to offer.
- 'Mode':
The model number of the generator. - 'Save@Recall':
The memory number in which you can save or have saved the complete settings for a signal. Use 'F4' (SAVE) and 'F5' (RECA) to save or recall the settings. - 'Sound':
Enable or disable the beeps the device emits with each action. - 'Language':
The language of the user interface: English or Simplified Chinese.
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| The 'System Setting” menu. (© 2026 Jos Verstraten) |
The PC software for the QLS3600S-10M
First, let's install LabVIEW...
Information and images regarding the available PC software are not easy to find on the internet. This is hardly surprising, as the designers of this device had the rather unfortunate idea of designing the software for this function generator for use on the LabVIEW platform. LabVIEW (Laboratory Virtual Instrument Engineering Workbench) is a graphical programming environment from National Instruments, developed specifically for professional measurement, control, test and automation applications. It is a very resource-intensive application that takes up 8 to 20 GB of space and requires a significant amount of system resources. Furthermore, during installation, LabVIEW makes deep changes to your Windows system. The software package modifies various system components to enable hardware control and real-time communication. Completely uninstalling LabVIEW is a complex process. Even after uninstalling the 'NI Package Manager', remnants are often left behind in the registry.
We find it fundamentally objectionable that software developers would impose such a heavy system load on a device as simple and hobbyist-oriented as the QLS3600S-10M. That is why we will not install this software on our PCs, nor will we promote it.
If you do need it, however...
You can download the necessary software from:
This 204 MB ZIP file contains:
- The runtime version of LabVIEW.
- Software that manages communication between the two devices.
- The actual software for operating the QLS3600S-10M.
Testing the QLS3600S-10M
Preliminary note
We are observing the output signals from the QLS3600S-10M on our OWON XDS2102A 100 MHz ~ 12 bit oscilloscope. To prevent signal attenuation and distortion caused by low impedances, we always use an OW3300 300 MHz 1/10 probe set to the attenuation mode. Naturally, we have first calibrated this probe perfectly. The QLS3600S-10M is powered by a 5.0 V power bank, completely disconnected from the mains.
The sine wave at various frequencies
We observe the waveform and, just as importantly, the amplitude of 10.00 V sine waves at frequencies of 10 Hz, 1 kHz and 10 MHz. As can be seen from the oscillograms below, the shape of the sine wave remains visually perfect right up to the highest frequencies. This is quite unique for function generators in this price range!
In all three oscillograms, the vertical gain is set to 2.00 V/div. What is also striking is that the signal amplitude remains virtually constant up to 10 MHz. This is even more unique! With most low-cost function generators, the signal is already considerably attenuated and distorted at the highest frequency.
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| The 10.00 V sine wave at various frequencies. (© 2026 Jos Verstraten) |
Generating small sine waves
In digital generators, digital noise pulses are always present in the output signal to a greater or lesser extent. With large output signals, these are barely noticeable. However, this changes when you set the amplitude to a low value. We tested this on the QLS3600S-10M by generating a 1 kHz sine wave with an amplitude of 100 mV. This corresponds to a rms value of 35.36 mV. As the oscillogram below shows, such low-cost digital function generators are, in fact, unsuitable for testing audio preamplifiers, for example. Far too much digital noise at the output! We'd much rather have a battery-powered analogue sine wave generator with a Wien bridge! That delivers undisturbed small signals.
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| A sine wave with a value of 35.36 mVrms. (© 2026 Jos Verstraten) |
Harmonic distortion on the sine wave
Inexpensive digital generators are not known for producing sine waves with low distortion. According to the specifications, the harmonic distortion should be less than 0.8 per cent, which is a fairly high figure for modern generators. To test this, we activated our Hameg HM8027 digital distortion meter and fed it with 5.0 V sine waves at frequencies of 20 Hz, 1 kHz and 20 kHz from the QLS3600S-10M. The measured values for harmonic distortion are:
- 20 Hz: 0.21%
- 1 kHz: 0.11 %
- 20 kHz: 0.08 %
The blue oscillogram below shows what the distortion on the 1 kHz signal looks like.
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| Harmonic distortion on a 1 kHz ~ 5.0 V sine wave. (© 2026 Jos Verstraten) |
Accuracy of the RMS value of the sine wave
We test this by connecting the output of the QLS3600S-10M to our EastTester ET3255 multimeter. The generator produces sine waves with various RMS values. We carry out this test at 1 kHz. We cannot enter the RMS value directly, but we convert it to amplitude each time. The results are shown in the table below, which clearly demonstrates that the accuracy leaves something to be desired at low voltages.
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| Accuracy of the RMS value of the sine wave. (© 2026 Jos Verstraten) |
Generating a sine wave burst
We're testing this at 1 kHz with a setting of five periods. Every time we press 'Out', the generator produces a nice burst. It's worth noting that the burst starts and stops neatly as the sine wave crosses zero. That's exactly how it should be!
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Generating a 1 kHz sine wave burst. (© 2026 Jos Verstraten) |
Generating square waves
An oscilloscope with a bandwidth of 100 MHz is not sufficient to properly evaluate a 10 MHz square wave. That is why we are limiting ourselves to 5 MHz. We set the QLS3600S-10 to an amplitude of 7.0 V and to frequencies of 1 kHz, 1 MHz and 5 MHz.
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| Display of square waves at 1 kHz, 1 MHz and 5 MHz. (© 2026 Jos Verstraten) |
The rise time of the square wave
According to the specifications, the rise time of the square wave voltage is a maximum of 20 ns. We check this on our oscilloscope (yellow trace). As the oscilloscope itself naturally has a rise time that cannot be ignored, we display the output voltage of our very fast pulse generator very fast pulse generator on the second (blue) channel. This has a guaranteed rise time of less than 0.18 ns. The rise time of the blue pulse is therefore caused by our oscilloscope. If you compare both rise times, you can conclude that the specified rise time of 20 ns corresponds fairly closely to reality.
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| The rise time of the square wave pulses. (© 2026 Jos Verstraten) |
Generating a narrow spike pulse
To conclude our test, we set the QLS3600S-10M to 'Pulse Out' mode and generated a pulse with a width of 20 μs.
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| A spike pulse with a width of 20 μs. (© 2026 Jos Verstraten) |
Our verdict on the Qletek QLS3600S-10M
We are very impressed with this affordable function generator. Of all the function generators we have tested in this price range, the QLS3600S-10M is undoubtedly the best. This assessment is based on the stability of the output voltage across the entire frequency range, the integrity of the signal shape at high frequencies and the high-quality square-wave generation. It is a pity that there is quite a lot of digital noise on small signals, making this generator less suitable for testing small-signal preamplifiers. After all, that noise is measured along with the signal when you record a frequency response curve, and that is not the intention.
Furthermore, we have rarely come across a device in this price range that offers so many features.
We have nothing positive to say about the way the PC-software has been designed. Virtually all similar devices have a single .EXE file of modest size, which allows you to control the device via a PC and design your own waveforms. Why the designers of the QLS3600S-10M opted for an application on the extremely resource-intensive LabVIEW platform is a mystery to us.
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