Products > Test Equipment
UNI-T UTG932/UTG962 200MSa/s Function Arbitrary Waveform Generator
Slartibartfast:
--- Quote from: wasedadoc on October 16, 2024, 04:25:11 pm ---
--- Quote from: Slartibartfast on October 16, 2024, 02:55:57 pm ---Hi,
got a UTG962E delivered today. Did some first measurements with it generating a square wave signal. It looks to be broken, as it appears specs are violated.
In this forum, some people had done rise time measurements reporting in-spec values of 15ns. The specs say 16ns. I measure approximately 22ns! See first screenshot below, taken with a Siglent SDS2504X+ and 50cm RG58 connecting the devices.
The signals at 10MHz and 20MHz look correspondingly awful. At 20MHz the third harmonic is not visible anymore at all, just looking at the oscillogram it is not distinguishable from a pure sine signal. In a proper square wave, the amplitude of the third harmonic is down by a faktor of three (as compared to the carrier), which is almost 10dB. With the third harmonic at the specified bandwidth frequency (60MHz), there is another 3dB attenuation, so I expect -13dBc. What I measure, is -34dBc!
At 10MHz, the signal actually looks as if the third harmonic is only just a little bit beyond the bandwidth limit, that would be 30MHz. The third harmonic is down by -18dBc. This is roughly what I'd expect at 20MHz, so I thought at first, I got a UTG932E with wrong labeling. However, the rise time violates the specs even in that case. In addition to that, the 10MHz square has a massive second harmonic, which should not be there at all.
Am I mistaken about anything, or should I really diagnose the device as "broken"?
--- End quote ---
Your first photo has "20M" in the bottom left corner. Is the scope's 20M BW limit turned on?
--- End quote ---
Oh, s**t. |O
I guess you're right. I had a hunch there was something wrong, that's why I asked here.
Thanks a lot!
Tomorrow I'll redo the test. Properly, this time.
Cheers Peter
Slartibartfast:
--- Quote from: Slartibartfast on October 16, 2024, 06:50:24 pm ---
--- Quote from: wasedadoc on October 16, 2024, 04:25:11 pm ---
--- Quote from: Slartibartfast on October 16, 2024, 02:55:57 pm ---Hi,
got a UTG962E delivered today. Did some first measurements with it generating a square wave signal. It looks to be broken, as it appears specs are violated.
In this forum, some people had done rise time measurements reporting in-spec values of 15ns. The specs say 16ns. I measure approximately 22ns! See first screenshot below, taken with a Siglent SDS2504X+ and 50cm RG58 connecting the devices.
The signals at 10MHz and 20MHz look correspondingly awful. At 20MHz the third harmonic is not visible anymore at all, just looking at the oscillogram it is not distinguishable from a pure sine signal. In a proper square wave, the amplitude of the third harmonic is down by a faktor of three (as compared to the carrier), which is almost 10dB. With the third harmonic at the specified bandwidth frequency (60MHz), there is another 3dB attenuation, so I expect -13dBc. What I measure, is -34dBc!
At 10MHz, the signal actually looks as if the third harmonic is only just a little bit beyond the bandwidth limit, that would be 30MHz. The third harmonic is down by -18dBc. This is roughly what I'd expect at 20MHz, so I thought at first, I got a UTG932E with wrong labeling. However, the rise time violates the specs even in that case. In addition to that, the 10MHz square has a massive second harmonic, which should not be there at all.
Am I mistaken about anything, or should I really diagnose the device as "broken"?
--- End quote ---
Your first photo has "20M" in the bottom left corner. Is the scope's 20M BW limit turned on?
--- End quote ---
Oh, s**t. |O
I guess you're right. I had a hunch there was something wrong, that's why I asked here.
Thanks a lot!
Tomorrow I'll redo the test. Properly, this time.
Cheers Peter
--- End quote ---
Ok, so here we go. With the scope bandwidth limit removed, the rise time looks good now. I measure slightly less than 15 ns now, which is clearly in spec and consistent with other people's measurements.
The bandwidth measurements using square wave signals did not improve that much, though. They indeed are more consistent with a 30 MHz device. In the 20 MHz output, the third harmonic is visible now, but still much weaker than it should be with 60 MHz bandwidth. The FFT quantifies it at -27 dBc, where theoretically -13 dB should be observed.
The 10 MHz measurement suggests the output of the UTG962E to be bandwidth limited to approximately 27 MHz, where it should be 60 MHz!
The harmonics go as Expected Excess
Harmonic Frequency (Theory) Measured Measured Attenuation
[MHz] [dBc] [dBV] [dBc] [dB]
1 10 0,0 -33,6 0,0 0,0
3 30 -9,5 -47,3 -13,7 -4,2
5 50 -14,0 -60,6 -27,0 -13,0
7 70 -16,9 -76,6 -43,0 -26,1
9 90 -19,1 -97,0 -63,4 -44,3
which shows a nice, smooth roll-off with the problem of the -3 dB point being somewhere around 27 MHz. I would call that quite acceptable for a 30 MHz device, like the UTG932E, but, as I wrote, this one is labeled and sold as a UTG962E.
Can somebody else with a UTG962E reproduce these results?
Cheers Peter
salomonander:
Can you elaborate on where to find this dBm option? I expected it in the sine menu but i cant find it. Im also not able to update my firmware due to some MD5 file that is supposedly missing :palm: anyone know what that means? Cheers
wasedadoc:
The 30 and 60 MHz numbers (for 932 and 962) are the highest sine wave output frequencies. Not BWs of the instruments. Harmonic content of the other output waveforms will be limited by the 16ns rise time.
wasedadoc:
--- Quote from: salomonander on October 17, 2024, 10:42:45 am ---Can you elaborate on where to find this dBm option? I expected it in the sine menu but i cant find it. Im also not able to update my firmware due to some MD5 file that is supposedly missing :palm: anyone know what that means? Cheers
--- End quote ---
Apologies. My previous answer was incorrect. Instead of relying on my memory I've dug mine out and turned it on. No dBm options. See below for hopefully final answer of "yes, does have dBm setting".
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