| Products > Test Equipment |
| What a crappy USB scope |
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| ivan747:
OK, I know they are actually crap, but I think my sound card input can do better than this! http://cgi.ebay.com/2-Channel-PC-Computer-Digital-mini-USB-Oscilloscope-/300544789091?pt=BI_Oscilloscopes&hash=item45f9dd8a63#ht_4792wt_802 For US $33.95 you get: Benefits: 2 channel input and synchronized display <-----Right, Iv'e never ever seen a scope that does that Records date, time and voltage in text file <-----I can haz a Rigol than can outputs teh CSV FIL3 Measures range automatically <-----Auto mode is useless here because you can't use the scope at all! 4 available modes: Low-pass filter mode, will get mains harmonics mode, computer crash mode and computer fire mode Input capture (trigger) function Able to set any channel as the source of the capture (trigger) signal <-----Notice there is no external trigger. Able to set rising or falling edge to capture (trigger) signal Adjustable capture (trigger) signal level Powered directly by USB port – no batteries or external power supply required <----- NO BATTERIES OR EXTERNAL POWER SUPPLY WILL GET FRIED, ONLY THE USB PORT WILL GET FRIED DIRECTLY. Use with electronic teaching equipment <----PERFECT FOR TEACHING WHY ENGINEERS SHOULD ADD INPUT PROTECTION Carry out acoustic tests and research <----- AS LONG AS YOU DO IT IN COWS, WILL NOT WORK ON MICE, YOU WILL SEE WHY IN THE TECH SPECS Ideal for SCM development Examine and repair apparatus and appliances Technical Parameters: PC connection: USB Operating systems used: W2K, XP ,Windows 7(32bit) <----YOU KNOW IT'S CHINESE CRAP WHEN THEY CALLIT W2K Signal input: BMC connection with universal oscillograph probe <----MISSPELLED BNC, OR INVENTED A NEW CONNECTOR Max sampling: 8kHz x 1/ (4kHz x 2) <------ I CAN PLUG A SPEAKER IN AND TELL YOU WHAT FREQUENCY IS IT Voltage: 5V USB port supply Current: 60mA Measurable frequency: 0Hz -----3kHz <------... DIV array: horizontal 16DIV x vertical 10DIV Input impedance: 1M? Max voltage: 0---5V <-----NOW I NEED ONE OF THOSE X100 PROBES. OH, WAIT, I CAN GET A REAL SCOPE FOR THAT PRICE... Error of voltage measurement: ±30mV <----- THAT'S 0.6% ACCURACY... AS LONG AS THEY THINK THE USB PORT'S VOLTAGE IS ±0.5%. DO YOU THEY THEY REALLY USE A VOLTAGE REFERENCE? Adjustable range of time domain: 10 mS/DIV----10800 S/DIV <----WHAT WE WANT TO LOOK AT IS TINY LOGIC SIGNALS, NOT THE VOLTAGE ACROSS A BATTERY BEING CHARGED. THAT'S WHAT DATALOGGERS ARE FOR. Error of time measurement: ±0.01% Capacity of data record & save: 8388608 x 2 Max time of data record & save: 93 hours <------OR UNTIL THE CRAPPY SOFTWARE ALGORITHM FILLS UP YOUR RAM Yeah, my very first forum rant ;D |
| ivan747:
By the way, what I do for not getting crap results out of eBay is search for: oscilloscope -vintage -nano -pocket -usb -digital -dso -avr -pic ^For analog only Tek 465-ish scopes ^ You can also add the "Used" filter on the left of the site. And I use: oscilloscope -vintage -nano -pocket -usb ^ For anything useful ^ You can add "-portable" for getting rid of unaffordable portable scopes. But the best way to solve that problem is to use the "Price" filter. Also be aware of the high shipping costs when shipping from China, avoid these "government surplus sale" items that end in hands of these online secondhand warehouses that have no idea about scopes and stick to the high end sellers. Get one with a picture of the scope working. If it's got technical specifications there's a good chance that the seller knows what's being sold. And if the seller is more inclined on giving only cosmetic information and telling you they "have no way of testing it" then it's probably one of those secondhand shops. |
| Zero999:
Someone at work was tempted to buy a 'scope like that for training he GCSE electronics students. I warned him off but I don't know whether he listened. I hope he did but don't I know because he left shortly. I didn't know him much but he did come across as the arrogant type. Are there any decent USB 'scopes? This one doesn't look bad: high resolution 9-bit per sample (better than many DSOs), 200MHz analogue bandwidth (probably only 100MHz is usable with both channels) and input over-voltage protection, although this is only 35V and probe ground is connected to the PC's protective earth. It's Windows only (so not and option for Mac or Linux users unless they use a VM) and there's no mention of whether Windows 7 is supported, although Vista is. http://www.hantek.net/Manual/5200A/DSO-5200AUSB_Manual.pdf http://cgi.ebay.co.uk/DSO-5200A-200MHz-PC-USB-Digital-Oscilloscope-VISTA-/260688504731?pt=UK_AudioElectronicsVideo_Video_TelevisionSetTopBoxes&hash=item3cb23ee79b |
| ejeffrey:
There are some reasonable USB based oscilloscopes, but they tend to be priced similarly to bench top units, or even higher. Gage makes some rather high end PCI and USB based scope modules but you don't want to know what the prices are. Their bread and butter is more for automated test setups and data acquisition than for general purpose debugging and product development. |
| ivan747:
--- Quote from: Hero999 on June 19, 2011, 03:24:48 pm ---Are there any decent USB 'scopes? --- End quote --- I don't think so, the USB 2.0 bus is too slow to give anything useful. At 8 bit sampling the maximuum theoretical speed without protocols is 480/8 Mbps which is 60 megabytes/sec. If they used Firewire or SCSI or maybe USB 3.0 they might be decent, but I've never seen anything like that and if there are any they would cost a LOT of money. It's just like those custom PCI interfaces. I've seen PCI-I2C bridges at 500 dollars! And they come in 5V and 3.3V versions. That's just to charge you with twice the money! With 4 simple signal MOSFETS and 2 GPIOs you could have done the same. Total cost increase: $0.50 Total extra programming time: 30 minutes. Anyway, that doesn't have to do with scopes. |
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