Rigol DS1052E oscilloscope: nasty surprise or it works fine? - Page 1
Forum section: electronics / beginners

author: NewBeginner
author_rank: Regular Contributor
timestamp: July 07, 2012, 11:06:35 am
content: Hi everybody,This is my first post on this forum so I hope I post in the right place.I am new to electronics (I just recently discovered this hobby of mine). I have read about oscilloscopes but I have never used one till now.I recently received (as a birthday gift) a brand new Rigol DS1052E oscilloscope. So I started digging for more information on howto operate it.In my quest I found this thread "https://www.eevblog.com/forum/blog-specific/rigol-ds1052e-nasty-surprise!/" (where "A Hellene" describes a nasty problem with this scope) and I began to worry about my scope (same model).So ... questions started to pop up in my head: does my scope suffer from the same defect? how would I be able to test it?Unfortunately my knowledge on this subject is close to zero. Even if I can take some measurements I am not able to interpret the readings.This is where I ask for your help. I did take some measurements but I can't tell if the readings are normal or if the scope is defective and suffers from the same problem as described by "A Hellene".I can't tell if the scope if generating too much internal noise or if it is operating in normal parameters.I would greatly appreciate it if you could tell me if the scope is operating properly or not.I attached screenshots for each measurement.To reduce external noise that might get picked up by the probes during measurements I tried to eliminate external noise sources. So I switched off all power in the apartment from the main panel, except for the circuit from where the oscilloscope was powered. I also switched of all electronic devices (cell phone, wireless thermostat, ...). So the only consumer in the apartment was the oscilloscope.Unfortunately I had no control on the neighboring apartments.The scope was operating for about 30-60 minutes before I took the measurements. Also for most of the measurements the scale was set to: 20mV / 5nsHere are the screen-shots and descriptions:1. Compensated probes: tip of probe connected to probe compensator connector andalligator clip connected to ground pin.2. No probes connected to the scope. Trigger set to AC line.3. No probes connected to the scope. Trigger set to CH1.The frequency counter changed periodically (usually between <5Hz and 30 Hz) but there also were some max values around 380Hz.4. Probe connected to scope but tip and aligator clip not connected to anything.Probe cable stretched out, tip away from the front of the scope.The frequency counter changed periodically (usually arund 250-350kHz) but there also were some max values of about 900kHz - 1.2MHz.Tip of the probe is close (3-5 cm) to the front of the oscilloscope. The probe cable forms a loop on the table (not sure if this info matters).5. Probe connected to scope and tip of the probe shorted to aligator clipBoth channels activated:6. Probe connected to scope. Tip of the probe held on the scop's mains cable.Thank you for your help

author: JuiceKing
author_rank: Regular Contributor
timestamp: July 07, 2012, 11:32:32 am
content: It all looks fine to me. The test with the calibration signal shows that it's basically working and your probe compensation looks good. You need to buy or build things that generate signals now. Forrest Mims book,Timer, Op Amp & Optoelectronic Circuits & Projectsbook describes lots of easy projects that will generate interesting signals. The book and required parts are all available at Radio Shack. Not a great place to get parts, but good enough to get started. Whatever you do, don't try to measure mains current directly with your scope. You'll blow it up and/or injure or kill yourself.

author: saturation
author_rank: Super Contributor
timestamp: July 07, 2012, 03:06:41 pm
content: It looks fine as is, but if you want to really see the noise you need to crank the input amp all the way up, IIRC thats to 2mV/div. Its best to short the input with a 50 ohm terminator rather than shorting the cables to avoid external noise pickup. IIRC correctly its < 5mVpp for noise.Congratulations on your new scope. Can you tell us what the firmware version is?

author: aghp
author_rank: Regular Contributor
timestamp: July 08, 2012, 08:57:49 am
content: Set it 5mV/div.CH1 and CH2 in useCH's BNC just open nothing connected ( hand not close to input and enviromet where is not high level of EMI noise "on the air")IF you have 50ohm terminator put it to CH1. If you have 2pcs then use CH1 and CH2 (if you do not have do not connect anything... Testing with probe connected and tip grounded with probe GND wire is just waste of time. (but with this kind poormans loop antenna you can find noises... try with computer LCD panel inverter (ner this you can pick up lot of with this prbe antenna)BW off.Horizontal time 1ms /div (or speed where it moves to scan mode, I do not remember if it was 100ms/div)Acquire modePeak!.Take a picturesDo same for 10mV/div and 20mV/div

author: NewBeginner
author_rank: Regular Contributor
timestamp: July 08, 2012, 04:54:56 pm
content: Thank you all for your help. I really appreciate it. I'm a little relieved now.@saturation Sure. The firmware version is: 00.02.06.Unfortunately I do not have a 50 Ohm terminator at hand now. I will try to purchase some from the local electronics store.@aghp In the manual I could only find references to "Slow Scan Mode" and "Delayed Scan Mode". So to which scan mode are you referring? I assume it is the slow scan mode (from the manual: "Slow Scan Mode: This mode is available when the horizontal time base is set to 50ms/div or slower "), right?I'll purchase some 50 Ohm terminators and I will redo the measurements and post some new pictures.Thank you.

author: aghp
author_rank: Regular Contributor
timestamp: July 08, 2012, 09:35:13 pm
content: Quote from: NewBeginner on July 08, 2012, 04:54:56 pmRight.And peak detect mode.if not use 50ms/div or more slow together with peak mode then:CH1, 5mV, 1ms/div, memory 1M and normal capture.

author: NewBeginner
author_rank: Regular Contributor
timestamp: July 08, 2012, 09:39:19 pm
content: Hi,Until I redo the noise measurements I have another question.Is it normal that sometimes the probes pick up the mains signal (as shown in the attached image) even if the tip of the probes are at about 25-40 cm from the nearest mains cable?The probes are connected to the scope but the tip and the ground clip are not connected to anything.Thank you

author: saturation
author_rank: Super Contributor
timestamp: July 09, 2012, 02:18:12 pm
content: Yes, it is. It shows how much electronics pollution surrounds you and how the devices you use have to filter them away. If you don't have a 50 ohm terminator just stick a 50 ohm resistor between the BNC cable inputs and keep the connectors to the resistor as short as possible. Enjoy, it looks great.Quote from: NewBeginner on July 08, 2012, 09:39:19 pm

author: NewBeginner
author_rank: Regular Contributor
timestamp: July 09, 2012, 04:16:20 pm
content: Hi,I purchased two 50 Ohm terminators and I redid the test.I tried to maintain the same environmental conditions as in the first tests.Also before I started to do the measurements I did a self calibration of the scope.So based on the new measurements is the unit working properly or does it suffer from excessive internal noise problems like described by "A Hellene"?Also I have two more question:1. I observed that without the 50 Ohm terminators connected the frequency counter showed a lower frequency than with the terminator connected (ex: image 7 is without terminator and image 1 is with terminator ). Why is that?2. The scope was set to X1 mode in order to be able to go down to 2mV/div. While the 50 Ohm terminators were connected they got pretty warm. Is this normal?Here are the images with the descriptions:1. No probes connected. Both inputs shorted with 50 Ohm terminators. Scale set to 2mV/div and 5ns/div. Measurement shown for CH1:2. No probes connected. Both inputs shorted with 50 Ohm terminators. Scale set to 2mV/div and 5ns/div. Measurement shown for CH2:3. Same as (2) but frequency counter shows a lower frequency and measurement shows a higher Vpp:4. No probes connected. Both inputs shorted with 50 Ohm terminators. BW limit off. Acquire: Peak. Scale: 5mV/div, 50ms/div :5. No probes connected. Both inputs shorted with 50 Ohm terminators. BW limit off. Acquire: Peak. Scale: 10mV/div, 50ms/div :6. No probes connected. Both inputs shorted with 50 Ohm terminators. BW limit off. Acquire: Peak. Scales: 20mV/div, 50ms/div :7. No probes connected. Inputs are free (not shorted with terminator):Thank you very much

author: saturation
author_rank: Super Contributor
timestamp: July 09, 2012, 05:39:53 pm
content: It looks great.

author: aghp
author_rank: Regular Contributor
timestamp: July 09, 2012, 07:38:57 pm
content: Simply: It looks good.

author: NewBeginner
author_rank: Regular Contributor
timestamp: July 09, 2012, 08:13:15 pm
content: Hi,Thank you all for your help. I appreciate it.I have one last question: while the 50 Ohm terminators were connected they got pretty warm. Is this normal?Thank you

author: saturation
author_rank: Super Contributor
timestamp: July 09, 2012, 09:04:17 pm
content: My guess is you are feeling the scope's internal temperature rising, with operation. Its easy to confirm, you need a thermocouple on your DMM or an IR laser thermometer and check the scopes operating temp, I think we measured it here about 30C. Now measure the temp of the terminator.It should not get warm for other reasons [ such as leakage current from the input amps], as otherwise the scope will not work, or at very least, to specification.Quote from: NewBeginner on July 09, 2012, 08:13:15 pm

author: NewBeginner
author_rank: Regular Contributor
timestamp: July 10, 2012, 06:52:29 am
content: Hi,To verify the scopes operating temperature I place the DMM thermocouple on the channel inputs (on the metal)?Thank you

author: A Hellene
author_rank: Frequent Contributor
timestamp: July 10, 2012, 12:55:46 pm
content: Hello NewBeginner,From the images you have posted, it seems that there is nothing wrong with your oscilloscope. Electrical noise is a basic (parasitic, though) attribute of every electrical or electronic device you can find; even at the much more expensive range ones.Examining your very first oscilloscope capture closely, both the channels seem to exhibit a ±0.05 divisions of noise, which is translated into an amount of ±50mV noise, since one division represents 1.00V. This is alright for this grade of oscilloscopes.QuoteYour first observation is an indication of the poor quality design/construction of that low quality-control series of test instruments, in general. Yes, with the terminator connected at the input, the noise reported should ideally be zero; but this never happens in the real world, even in much more expensive similar devices. The ideal readout with a terminator connected at the input should be what the instrument reports when you set the input coupling to ground; but even the top-notch equipment cannot achieve that level of noise immunity.On the terminator heating issue you observed, the terminator being a metallic object it is just transferring (by mechanical contact) the BNC/PCB heat outside the instrument casing, acting as a heat-sink. The PCB is being heated up by the several voltage regulators it has directly soldered on its top layer (seven of them in total!) as well as by the other high-frequency (analog and digital) components that also generate heat while they are working. If you can excuse my ASCII art, you can see theDS1000E mainboard PCB components layoutand its power distribution scheme.Let me also add the fact that I could feelthe problematic devicehaving its PCB working in a slightly higher temperature than the normally functioning one did. This can be explained by the slightly higher power consumption of the PCB that hadself-oscillatingstages, which were drawing and dissipating more power because of their internal individual components transients in very high frequencies all the time due to their self-oscillation in the VHF region.Anyway, I should not be intimidating you any further! As I wrote before, along with many members of this forum, your device does not seem to be faulty; it seems to be working as expected. Just try to enjoy your new device, while learning electronics; especially, the nasty side of electronics!-George

author: NewBeginner
author_rank: Regular Contributor
timestamp: July 10, 2012, 09:43:45 pm
content: Thank you all for your helpI already measured the temperature with a DMM, before I read the last posts, and it seems that it is the same with or without the 50 Ohm terminations connected (around 33-35C).Ambient temperature was around 28-29C (yes, it is a hot weather here these days)All looks good. Now it is time to build some circuitsI already have some other questions in my mind about working with the oscilloscope but those are for another thread.Thank you.