Issue with new digital oscilloscope from aliexpress

Thread Starter

Yuseph

Joined Jun 8, 2020
45
Hey guys,

Wow this oscilloscope from aliexpress got me lost. Ive set my AC AC converter to 12VAC. My multimeter shows 13.90vac and notice its written true rms on it !
Next to that, my oscilloscope shows Vrms 11.4vac. ive set it to 5v/div. When i set it to 1v/div its even worse it shows 4.11vac. whats going on guys ?
20200721_210407.jpg
 

KeithWalker

Joined Jul 10, 2017
1,149
Over-driving it how ??
The display on your scope is cutting off the bottom of the displayed trace. You need to change the range on the Y input to 10V/Div so that the whole trace is displayed. You also have a DC offset on the displayed signal. For a symmetrical AC signal, 0V should be half way down the screen. This could be because you have not adjusted the display DC offset. Check your instruction sheet. The scope is only showing the amplitude of the section of the trace that is being displayed. That's why the reading goes down when you increase the input sensitivity.
Keith
 
Last edited:

MrChips

Joined Oct 2, 2009
21,682
AC power adapters do not output the rated voltage.
The voltage output will fall as power is taken from the adapter. For a conservatively rated adapter it should mean the RMS AC voltage of 12V will be available at full power output. Not all manufacturers stay true to the specs.
 

Thread Starter

Yuseph

Joined Jun 8, 2020
45
The display on your scope is cutting off the bottom of the displayed trace. You need to change the range on the Y input to 10V/Div so that the whole trace is displayed. You also have a DC offset on the displayed signal. For a symmetrical AC signal, 0V should be half way down the screen. This could be because you have not adjusted the display DC offset. Check your instruction sheet. The scope is only showing the amplitude of the section of the trace that is being displayed. That's why the reading goes down when you increase the input sensitivity.
Keith
Damn you solved the problem instantly. The V / div must be set to a range close to the output voltage. What isnt displayed isnt counted in. I didnt know that. Also i had to set both the probe and ch2 to x10 instead of x1. Because x1 doesnt go beyond 5v.
Sorry guys first oscilloscope first try.
 

Thread Starter

Yuseph

Joined Jun 8, 2020
45
AC power adapters do not output the rated voltage.
The voltage output will fall as power is taken from the adapter. For a conservatively rated adapter it should mean the RMS AC voltage of 12V will be available at full power output. Not all manufacturers stay true to the specs.
When i set the ac power adapter to 12v i get 14vrms on the oscilloscope and 13.75 vrms on the multimeter. This german brand profitec is the only ac power adapter i could find on the market.
 

SamR

Joined Mar 19, 2019
2,419
The reverse is also true. To get the best from the DAC in the scope the input should be scaled to fit the display. Some of that is done in the preamp to the DAC but the output image, for best resolution, should be as large as possible without clipping.
 

sparky 1

Joined Nov 3, 2018
302
Does the manual show recommended power. The charging system supports the 6000 mah lithium ion battery a complete specification sheet is not found even on the marketing website. Ebay only shows this summary.
The chargers that plug into car cigarette lighter plug preferable heavy duty 5V 2A will be safe until you know otherwise.
Probably 13.8 V is correct and should say in the users manual.

When you get a chance can you show the FFT please.

Model: FNIRSI 1013D
Type: Oscilloscope
Bandwidth: 100MHz x 2(Dual Channels)
Channel: 2 Channels
Max. Real-Time Sampling Rate: 1GSa/s
Vertical Sensitivity: 50mV/div to 500V/div
Time Base Range: 50ns/div - 10s/div
Max. Testing Voltage: 40V (1 x Probes), 400V (10 x Probes)
Storage Depth: 240Kbit
Input Resistance: 1M
Coupled Mode: AC/DC
Trigger Function: Single, Normal, Automatic
Trigger Edge: Rising Edge, Falling Edge
External Trigger Voltage: 0-40V
Operation Method: Screen Touch, Gesture
Power Source: 6000mAh Rechargeable Battery(Included)
Vibrator Size: 184mm x 124mm x 50mm/7.24" x 4.88" x 1.96" (Approx.)

Note:
Due to the light and screen setting difference, the item's color may be slightly different from the pictures.
Please allow slight dimension difference due to different manual measurement.

Package Included:
1 x FNIRSI 1013D Oscilloscope
2 x 100MHz Probes
1 x 5V/2A Charger with USB Cable
1 x User Manual
 

Thread Starter

Yuseph

Joined Jun 8, 2020
45
I have no
Does the manual show recommended power. The charging system supports the 6000 mah lithium ion battery a complete specification sheet is not found even on the marketing website. Ebay only shows this summary.
The chargers that plug into car cigarette lighter plug preferable heavy duty 5V 2A will be safe until you know otherwise.
Probably 13.8 V is correct and should say in the users manual.

When you get a chance can you show the FFT please.

Model: FNIRSI 1013D
Type: Oscilloscope
Bandwidth: 100MHz x 2(Dual Channels)
Channel: 2 Channels
Max. Real-Time Sampling Rate: 1GSa/s
Vertical Sensitivity: 50mV/div to 500V/div
Time Base Range: 50ns/div - 10s/div
Max. Testing Voltage: 40V (1 x Probes), 400V (10 x Probes)
Storage Depth: 240Kbit
Input Resistance: 1M
Coupled Mode: AC/DC
Trigger Function: Single, Normal, Automatic
Trigger Edge: Rising Edge, Falling Edge
External Trigger Voltage: 0-40V
Operation Method: Screen Touch, Gesture
Power Source: 6000mAh Rechargeable Battery(Included)
Vibrator Size: 184mm x 124mm x 50mm/7.24" x 4.88" x 1.96" (Approx.)

Note:
Due to the light and screen setting difference, the item's color may be slightly different from the pictures.
Please allow slight dimension difference due to different manual measurement.

Package Included:
1 x FNIRSI 1013D Oscilloscope
2 x 100MHz Probes
1 x 5V/2A Charger with USB Cable
1 x User Manual
I havent tried their charger. Those lazy nerds sent me an american adapter. Im using a universal adapter instead. Its still charging and its been more than 6 hours now. It make takes 10 hours.
 

Attachments

MrChips

Joined Oct 2, 2009
21,682
There is nothing wrong with the adapter or the oscilloscope. Your input signal is saturating. Go to a higher input voltage scale.
 

KeithWalker

Joined Jul 10, 2017
1,149
When i set the ac power adapter to 12v i get 14vrms on the oscilloscope and 13.75 vrms on the multimeter. This german brand profitec is the only ac power adapter i could find on the market.
The difference between the readings on the scope and voltmeter can be caused by several things. The first is the purity of the sinewave. We can't see that on your scope pictures but if you decrease the time/div of the timebase, the waveform will spread out and you will be able to see if it is very distorted. There will also be a difference in the way the AC measurements are made. Either could be using a peak detector or an average detector with a conversion factor to RMS, or a true RMS detector. The meter is probably the most accurate on AC voltage measurements.
Keith
 

tautech

Joined Oct 8, 2019
123
Model: FNIRSI 1013D
Type: Oscilloscope
Bandwidth: 100MHz x 2(Dual Channels)
Channel: 2 Channels
Max. Real-Time Sampling Rate: 1GSa/s
Vertical Sensitivity: 50mV/div to 500V/div
Time Base Range: 50ns/div - 10s/div
Max. Testing Voltage: 40V (1 x Probes), 400V (10 x Probes)
Storage Depth: 240Kbit
Input Resistance: 1M
Coupled Mode: AC/DC
Trigger Function: Single, Normal, Automatic
Trigger Edge: Rising Edge, Falling Edge
External Trigger Voltage: 0-40V
Operation Method: Screen Touch, Gesture
Power Source: 6000mAh Rechargeable Battery(Included)
Vibrator Size: 184mm x 124mm x 50mm/7.24" x 4.88" x 1.96" (Approx.)

Note:
Due to the light and screen setting difference, the item's color may be slightly different from the pictures.
Please allow slight dimension difference due to different manual measurement.

Package Included:
1 x FNIRSI 1013D Oscilloscope
2 x 100MHz Probes
1 x 5V/2A Charger with USB Cable
1 x User Manual
Extended discussions about these over on the EEVblog forum as to they don't meet published BW spec.
Also the 50mV max sensitivity is severely limiting when using a 10x probe as we mostly do as it becomes 500mV max sensitivity that is a major handicap for a plethora of tasks.
 
Top