Electronics > Beginners
My purchase list for my new lab -- budget $1000+, thoughts?
nanofrog:
The regular EEVBlog discount is only 6%. Here.
AnyNameWillDo:
Should I be getting something better than the Rigol DS1054Z (when unlocked to 100 MHz), then?
rstofer:
--- Quote from: jrd on July 22, 2018, 09:53:03 pm ---
1. Not sure how valuable a 4 channel scope is for you. Dont forget a 50 MHz DSO at 4 channels = 50 / 4 = 12.5MHz max sample rate if all channels are enabled. This means if you intend to use all 4 channels at the same time for Digital Work, its going to be for very slow 1980s type TTL and CMOS speed circuits. You might be better served by two channels at 100 or 200 MHz for alittle less money, and a purchase of some nice high impedance scope probes to go with the instrument.
--- End quote ---
I don't think this is correct. The 4 channel DS1054Z samples at 1 GHz. We divide that across 4 channels and get 250 MHz which just turns out to be the magic "2.5" number that is typical for sampling. You need to sample at least 2x (Nyquist and Shannon) and 2.5x is the industry standard. All 4 100 MHz channels are sampled at 250 MHz. ETA: Minimum of 250 MHz, turn off unused channels for higher sample rate.
The actual 3 dB bandwidth of the 100 MHz unlocked DS1054Z has been shown to be around 130 MHz. There a video somewhere...
The closest 4 channel 200 MHz scope is the Siglent SDS1204X-E and it is nearly $800. Their 100 MHz 4 channel is competitive with Rigol and their 2 channel is quite reasonable. We have had this discussion almost weekly since the Siglent was released. Had the more expensive 1204 been available, I would have bought it for the bandwidth. Alas, it wasn't so I bought the Rigol. Some day I might buy the Siglent but I'll let them finish up the firmware. I'm not in a hurry. Nor do I know what issues remain in the firmware, if any.
In a scope, bandwidth is everything, except channels. I wanted 4 channels for SPI and I already had bandwidth in my Tek 485 (350 MHz).
rhb:
--- Quote from: jrd on July 22, 2018, 09:53:03 pm ---
1. Not sure how valuable a 4 channel scope is for you. Dont forget a 50 MHz DSO at 4 channels = 50 / 4 = 12.5MHz max sample rate if all channels are enabled. This means if you intend to use all 4 channels at the same time for Digital Work, its going to be for very slow 1980s type TTL and CMOS speed circuits. You might be better served by two channels at 100 or 200 MHz for alittle less money, and a purchase of some nice high impedance scope probes to go with the instrument.
--- End quote ---
The DS1054Z will sample a single channel at 1 GSa/S, two channels at 500 MSa/S and 3-4 at 250 MSa/S. I have had a DS1102E for several years which has generally been satisfactory. I was considering the DS1104Z-S, but in the end bought an Instek MSO-2204EA for the better FFT and higher BW.
I have doubts about the quality of the calibration of a "hacked" DS1054Z, but no doubts about the instrument itself. It is certainly an excellent choice for a beginner's scope. The sample rate limitations using 3-4 channels. make it a better 50 MHz DSO than a 100 MHz DSO. At 50 MHz you have 5 samples per cycle rather than only 2.5 which is just barely better than the Nyquist limit of 2 samples per cycle. The sharp cutoff anti-alias filter required at 2.5 samples per cycle leads to a lot of ringing on a step response.
mathsquid:
--- Quote from: rhb on July 22, 2018, 07:07:19 pm ---
--- Quote from: mathsquid on July 22, 2018, 05:35:07 pm ---
--- Quote from: rhb on July 21, 2018, 11:45:04 pm ---Mains powered equipment is not dangerous if it is unplugged.
--- End quote ---
Is that true of a switch-mode power supply?
--- End quote ---
As noted, in either instance you do need to have the sense to discharge the capacitors before touching the terminals.
For pete's sake, this is an electronics forum....
--- End quote ---
But the person who started the thread is presumably very new to electronics, so I thought that the blanket statement "mains powered equipment is not dangerous if it is unplugged" needed some follow-up.
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