{"id":1845,"date":"2013-08-23T21:53:29","date_gmt":"2013-08-24T05:53:29","guid":{"rendered":"http:\/\/pididu.com\/wordpress\/?p=1845"},"modified":"2017-01-06T15:54:28","modified_gmt":"2017-01-06T23:54:28","slug":"i-dropped-an-oscilloscope-on-my-foot-hantek-6022be","status":"publish","type":"post","link":"http:\/\/pididu.com\/wordpress\/blog\/i-dropped-an-oscilloscope-on-my-foot-hantek-6022be\/","title":{"rendered":"I Dropped an Oscilloscope on My Foot! (Hantek 6022BE)"},"content":{"rendered":"

When I was in high school, if someone said they dropped an oscilloscope on their foot, it would be cause to go to the office for first aid, or possibly even call an ambulance. Today, if I dropped this scope on my foot, I would be more worried about the scope than my foot.<\/p>\n

\"Two<\/a>
Two channel, 48 Msps digital scope weighs 13.3 ounces<\/figcaption><\/figure>\n

The Hantek 6022be digital oscilloscope weighs 13.3 ounces, and is a wonderful example of how technology gets cheaper and better with time. \u00a0The line cord alone of an old analog oscilloscope might outweigh this tiny model. \u00a0And by the way, the Hantek has no line cord – it draws all it needs from USB, though its PC connection. I bought this instrument on eBay for $69.14, with free shipping. \u00a0Not since Adventures in Babysitting<\/strong><\/em> have I had such low expectations for something, and been so pleasantly surprised. \u00a0For that paltry price, I got the scope, two probes that are settable for x1 or x10, and the software.<\/p>\n

This model has most of the features of the analog scopes of yesteryear, including a built-in calibration source. \u00a0It is, of course, a storage scope, and can send output directly to a printer, or save it in a variety of file formats, including bitmap and spreadsheet. \u00a0There is also the handy feature of time, voltage, and frequency measurement by just dragging a cursor.<\/p>\n

My first use of this scope was to debug an overheating problem<\/a> on a DC-DC converter circuit. \u00a0This was a tough problem to diagnose without a scope, but is now trivial. \u00a0I was blind, but now I see.<\/em> \u00a0Below is the troublesome driver circuit for the main power MOSFET. \u00a0R5 is driven directly from a processor output pin.<\/p>\n

\"DirectDrive\"<\/a>
A train of positive-going pulses is input on the left<\/figcaption><\/figure>\n
\"trace1\"<\/a>
No wonder the MOSFET was burning up! Look at that crappy rise and fall time. It’s like 4 \u03bcS for each transistion, which is horrible, considering this is only a 4.7 \u03bcS pulse. \u00a0Any time the transistor isn’t fully on or fully off, it’s wasting power. As a side note, observe the little nick in the rising waveform, marking the place where the transistor turns on and starts charging the Miller capacitance.<\/figcaption><\/figure>\n

Okay, so I got rid of the resistor, and drove the MOSFET directly from the processor pin:<\/p>\n

\"trace2\"<\/a>
Better, but I’m still not happy with the risetime.<\/figcaption><\/figure>\n

The next thing I tried was a complementary pair of small MOSFETS as a driver:<\/p>\n

\"MOSTotemDrive\"<\/a>
Note that the incoming pulse had to be inverted in software. No big deal.<\/figcaption><\/figure>\n
\"trace4a\"<\/a>
The transitions are quick, but that falling edge rings like the phone of a guy who just won the lottery.<\/figcaption><\/figure>\n

The scope didn’t come with a manual, but I’m slowly figuring out how to use it. To move the channel 1 trace up and down, all I have to do is drag the yellow “1” la<\/span>bel up and down. The trigger level can be adjusted in a similar manner. To pan the trace right or left, I simply drag it, like a Google map. Below is a trace with the ringing dragged up where we can see it:<\/p>\n

\"trace4b\"<\/a>
The trace is moved up to show the ringing more clearly. \u00a0Looks like it’s 5 volts peak to peak!<\/figcaption><\/figure>\n

Some of the ringing above is a consequence of my test setup, which has a foot-long wire going to the gate of the transistor, and a foot-long ground return. The following trace was taken at the driver instead of the gate of the transistor:<\/p>\n

\"trace4c\"<\/a>
The ringing is not severe at the actual complementary pair output. This is likely more representative of what the real circuit will do on a PC board.<\/figcaption><\/figure>\n

I put a 15\u03a9 resistor between the complementary pair and the gate of the power MOSFET, and measured at the gate again:<\/p>\n

\"trace5\"<\/a>
With a 15\u03a9 series resistor on the gate of the power MOSFET, the ringing is mostly gone. \u00a0Although the actual design might not need it, I will put space for such a series resistor on the PC board just in case.<\/figcaption><\/figure>\n

It’s advertised as a 20 MHz scope, but that’s basically the Nyquist rate, so I thought it was marketing hype. But then, I took the following trace:<\/p>\n

\"Surprisingly,<\/a>
Surprisingly, the scope was able to show this ringing at over 20 MHz. The instrumentation says 2 MHz, but note that I have the cursor set to measure 10 cycles.<\/figcaption><\/figure>\n

And now, some of the drawbacks of the 6022BE:<\/p>\n

    \n
  1. There is only DC coupling. \u00a0If you want AC, you’ll need to build your own test jig.<\/li>\n
  2. The triggering has no noise filter on it, so is very erratic. \u00a0The trace buffer is usually deep enough to capture what you want, but it might take several tries, and\/or you might have to scroll through a lot of data.<\/li>\n
  3. Speaking of scrolling, there are no scroll bars, a serious user interface deficiency. \u00a0As the software stands today, you can drag the screen right or left, but with a deep buffer, may have to drag literally hundreds of screens to get to the point of interest. \u00a0What is really needed is the ability to zoom in on a chosen area. \u00a0Perhaps that will be added in a later version of software.<\/li>\n
  4. The software does have the ability to export the data buffer as a text file, so maybe someone could write a utility to display and zoom the trace offline.\u00a0 However, the values output in the text file might need adjustment.\u00a0 I measured a known 5.2 volt signal, and the text file said it was 6.2 volts.<\/li>\n
  5. Triggering is not reliable, especially at high speed sweeps, and especially in single sweep mode.\u00a0 I suspect<\/strong> that what the software does is blindly capture a data buffer, then scan to see whether there is a trigger event in it.\u00a0 If no trigger is found, the software then captures another data buffer.\u00a0 Needless to say, at high sweep rates, there is a lot of deadtime between capturing buffers while the software is busy looking at the captured buffer.\u00a0 If a trigger event should occur within this deadtime, the trigger would be missed.\u00a0 For repetitive signals, this is less of an issue, as sooner or later, by plain dog luck, a trigger event will be captured.<\/li>\n
  6. The scope is NOT isolated from USB ground, which on a computer is typically connected to the ground on the wall plug. You cannot connect the ground clip of a probe to (say) line voltage to take a reading. You’ll need to either use an isolation transformer, or a laptop running on batteries (not plugged in) to do this sort of thing without blowing something up.<\/li>\n
  7. There is no mention in the specs, but it seems that actual input voltage to the scope is limited to 5 volts. This is not surprising, since the USB voltage is 5 volts. So if you use the included 10:1 probe to measure something that is (say) 75 volts, it will read as 50 volts. If you want to measure between 50 to 500 volts, you need a 100:1 probe, not included.\u00a0 Of course, if you wanted to be cheap about it, you might just put a 90 M\u03a9 resistor in series with the included probe.<\/li>\n
  8. The software only works on Windows XP and later. It does not load on Windows 2000. If you have Windows 7 or later, you need to go to the Hantek site to get drivers that are not on the included CD. There is OpenHantek software that runs on linux, but it does not support the 6022BE at this time (2013). \u00a0If you are handy with software, you could make a lot of friends by porting this open source software to work with the 6022BE. There is also some software called Open6022BE being developed here<\/a> by a user named “RichardK,” with documentation by “Matchless,” and testing from the community at large. At this writing (March 2014), the software is still in Beta, but I find it so much better than the stock software, that I already use it on my home bench. For your convenience, I have mirrored the Open6022BE software and source here<\/a>. UPDATE (22-Dec-2016): I have written my own open source alternative software. You can get BasicScope here<\/a>.<\/li>\n
  9. Do not expect any support from the manufacturer in China. Their site is very sparse with English help.<\/li>\n
  10. The scope trades off sample rate and sample size; you cannot get the 48 MHz sampling at the same time as the 1 MB buffer. Once you set the sweep rate (time per division), the sample rate and size are fixed per the table below. Data from Rick Law on this forum<\/a>, plus a bit of data I filled in for completeness.<\/li>\n<\/ol>\n\n\n\n\n\n\n\n\n\n\n\n
    Time per Division<\/th>\nSample Rate<\/th>\nSample Size (per channel)<\/th>\n<\/tr>\n<\/thead>\n
    50 mS or longer<\/td>\n1 MHz<\/td>\n1,047,552<\/td>\n<\/tr>\n
    5 to 20 mS<\/td>\n1 MHz<\/td>\n523,264<\/td>\n<\/tr>\n
    50 \u00b5S to 2 mS<\/td>\n1 MHz<\/td>\n130,048<\/td>\n<\/tr>\n
    20 \u00b5S<\/td>\n4 MHz<\/td>\n130,048<\/td>\n<\/tr>\n
    10 \u00b5S<\/td>\n8 MHz<\/td>\n130,048<\/td>\n<\/tr>\n
    5 \u00b5S<\/td>\n16 MHz<\/td>\n130,048<\/td>\n<\/tr>\n
    2 \u00b5S or shorter<\/td>\n48 MHz<\/td>\n1,016<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    In spite of the above, I’m still super-pleased with my purchase.<\/p>\n","protected":false},"excerpt":{"rendered":"

    When I was in high school, if someone said they dropped an oscilloscope on their foot, it would be cause to go to the office for first aid, or possibly even call an ambulance. Today, if I dropped this scope on my foot, I would be more worried about the scope than my foot. The … Continue reading I Dropped an Oscilloscope on My Foot! (Hantek 6022BE)<\/span> →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":1854,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[66],"tags":[74,65,49,61,64,63,221,62],"_links":{"self":[{"href":"http:\/\/pididu.com\/wordpress\/wp-json\/wp\/v2\/posts\/1845"}],"collection":[{"href":"http:\/\/pididu.com\/wordpress\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/pididu.com\/wordpress\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/pididu.com\/wordpress\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/pididu.com\/wordpress\/wp-json\/wp\/v2\/comments?post=1845"}],"version-history":[{"count":0,"href":"http:\/\/pididu.com\/wordpress\/wp-json\/wp\/v2\/posts\/1845\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/pididu.com\/wordpress\/wp-json\/wp\/v2\/media\/1854"}],"wp:attachment":[{"href":"http:\/\/pididu.com\/wordpress\/wp-json\/wp\/v2\/media?parent=1845"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/pididu.com\/wordpress\/wp-json\/wp\/v2\/categories?post=1845"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/pididu.com\/wordpress\/wp-json\/wp\/v2\/tags?post=1845"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}