I feel like the man or woman in the commercial who says "I could have had a V8." Back in the spring Circuit Specialists had a sale on their very best line of DSOs (Digital Storage Oscilloscopes). Within my budget I had a choice of a 200 MHz 2 channel or a 100 MHz 4 channel scope. Faced with a decision I decided that I would be more likely to use the extra 100 MHz than the extra two channels. About 4 months after making that decision I found to my surprise a 4 channel scope on Amazon, of all places, for 399 dollars. If you add that to what I spent on the 200 MHz 2 channel I could have had the 4 channel 200 MHz for just a little more. Unfortunately my cash flow didn't permit the more desirable option so instead of one really good scope I have two, one almost as good and the other one…well I'll give you the facts and you can make up your own mind.
The name seems a little strange. I wonder if they were aiming to name their company after the star Rigel and missed the target. That's neither here nor there, the name is what it is.
Except for having 4 channels It looks and acts similar to the other 3 DSOs I own.
It is advertised as a 50 MHz scope. The response is down -0.72 dB at 50 MHz and -1.31 dB at 80 MHz. That's as high as my bench function generator goes and I am not inclined to fire up the HP 608 to find the upper -3 dB point. Suffice it to say that you can do some useful work with it well above 50 MHz. Triggering is reliable and the trace is steady at these VH-Frequencies. (Note: Others might have written VHF frequencies. That would be to say "very high frequency frequencies". That's another for my collection of redundancies. My favorite is PIN number.)
The vertical sensitivity goes from 10 mV/div to 100 v/div using a times ten probe.
The horizontal sweep goes from 50 s/div to 5 ns/div.
Trigger sources are CH1, CH2, CH3, CH4, and line. No external trigger. I guess the designers figure that with 4 input channels there is likely to be one left over to be used as a trigger channel.
The list of probes is a long one as shown below. It goes from 0.01X to 1000X in a 1, 2, 5, sequence. I provide this picture to show you how the menus work which is a little different from other DSOs. The selection on the menu can be changed by pressing the button again, (in this case the soft key next to "Probe"), the effect, if any, appears on the screen but the menu does not go away. The selection can also be changed by rotating the universal knob but the effect is not shown. The menu does not go away until the universal knob is pushed in until it clicks. If you set the menu to the setting you desire by pressing you will be there a long time if you wait for the menu to be removed. I push the knob with my thumb which seems to impart a small rotation to the knob which selects the item just below the one I wanted just an instant before the click. All of the popup menus work this way.
Screen shot showing probe menu.
When the trigger button is pressed the trigger menu comes up on the right edge of the screen. It is identified by the word "Trigger" in text that is read upwards next to the menu. Pressing the settings soft key will pull up a submenu that has the familiar settings of coupling (AC, DC, LFR, and HFR, low frequency reject and high frequency reject.) Hold off from 16 ns to who knows how high, and noise reject, (on and off).
On the Math menu three of the four selections apply to the logic analyzer option which is not enabled in this model. Pressing the "Math" button calls up a long list of functions. Here goes. A+B, A-B, AxB, A/B, FFT, A and B, A or B, !A, intg (integral), dif (dv/dt), Lg (Log), ln, exp (e^x) Abs, and Filter. The presents of a log function makes it, at least, theoretically possible to plot a function in dB. However, the dynamic range is limited by noise which limits the usefulness of this function. More about noise later.
Cursors are the best thing that digital technology added to the oscilloscope. The ones on this scope are easy to read and easy to control.
Cursors are very helpful.
What makes cursors so powerful is that they are under operator control. The trace on a scope usually has finite width and the most correct reading is at the center of the trace not the outer edge. (OK, so I missed a little when setting the upper cursor. Are you going to make a federal case of it?)
This is not the recommended way of finding the wavelength. The exact location of the peak is hard to find. The proper way is to set the horizontal cursors on parts of the wave that have a large slope using a graticule line for consistency.
If you are content with automatic measurements you can get a ton of them by pressing the Measure button. It does include some which will send you reaching for your calculator. Such as but not limited to, RMS.
If you don't want to call up the whole 9 yards try this. From the displayed waveform press one of the soft keys on the left side of the screen. This is another measurement menu and is always on.
There is space for a maximum of 5 quantities. If more are added the newest will appear on the right and older ones will scroll off the left side. Note on the right that the Acquire menu is up and it is set to average. This gives a finer trace and improves the accuracy of all measurements. The number of averages is only 2 but that makes a big difference. Setting it to 4 or 8 will improve things further but it may take a while on low frequency signals.
The bad news.This would be a really good scope except for one thing. There is a tremendous amount of noise in the input amplifiers. The two screen shots below show the noise, one with two coaxial cables feeding directly from the function generator to the scope and the other using two of the provided 10X probes.
Coax cables directly from function generator to scope.
Times ten probes used between function generator and scope.
So the test would be fair I left the volts/div control set to the most sensitive range for both tests. I did not change the probe setting to make this clear. Because of the large amount of noise the sweep couldn't figure out how to trigger. I had to use the run/stop button to stop the processor and catch the wave in a stable position. The acquire menu shown in the second screen shot shows the mode set to normal.
For the second picture it was necessary to increase the output of the generator by a factor of 10. If the generator had been contributing all of the noise the traces would be 1/10 as thick in the second picture. It might be argued that the generator is contributing some noise because the traces are thinner in the second picture. However, other tests I did indicate that the effect is one of impedance level. The input amplifiers seem to produce more noise when the input is terminated with the low impedance of the generator (50 ohms) as opposed to the high impedance probe.
Although only two channels are shown all 4 produce the same amount of noise. This eliminates the possibility of one bad part. Between the input connectors and the attenuators all 4 channels have their own set of parts including the attenuators. With all 4 channels being effected the problem is either in the design or the choice of components.
The next screen shot shows that the noise can be overcome by using the average mode in the acquire menu.
Average mode reduces noise by a considerable amount.
However, one cannot use average mode for all situations. Waves which are not in sync will be greatly reduced in amplitude and can totally disappear. This includes amplitude modulation envelopes when the modulating signal is used to trigger the sweep.
Upon Further Reflection.Much useful work can be done with this scope in spite of its limitations. Back in the day of the Tektronix 531 and 545 we did a lot with sensitivities that only went down to 100 mV per div (with 10X probe). Here is the same setup with the same generator at that input sensitivity setting.
Noise is reduced by operating at a higher input level.
While the traces may be a little thicker than we might desire consider this sensitivity setting to be the lower limit and things will get better at higher input voltages and higher V/div settings.
Setting the clock.Setting the clock is more important than you might imagine. When a screen shot is taken the file date and time are written by the scope. I sort these files by date so the ones I am working with will be at the top. The pictures from this scope are way down the list in the ancient history section.
The scope's calendar/clock is frozen at 1:00 PM on November 1, 2014. The Manual and the scope's help system is silent on the subject. I can't find time/date or clock anywhere in the menus.
The Manual.The manual provided is in three languages and I must say that the English is not broken or even damaged. But there isn't enough of it. It provides little that an experienced DSO user doesn't already know.
I give the scope 3 stars.
I'm not going to give a link to Amazon. If you want one of these scopes you can find it yourself. I tried to post a shortened version of this review there and apparently they have rejected it. If you do a little sniffing around up there you may find where I gave a positive review to a printer and a negative review to a 6 dollar set of clip leads that are just like the ones that Radio Shack used to sell. They fall apart after 3 or 4 uses. But a negative review of a 400 dollar scope was apparently more than they could swallow. So just like anywhere else it's caveat emptor (let the buyer beware).