Some Pre-purchase questions

Some Pre-purchase questions, a forum discussion on Cleverscope. Join us for more discussions on Some Pre-purchase questions on our Questions forum.

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23 May 2009
Posts:

Looking to buy an USB scope, I checked out your offerings as well. I am leaning towards a CS320A with the CS700A signal generator and CS714U for improved resolution.
Before deciding, I have a few questions regarding the Cleverscope 320A:

1.) In the comparison sheet (http://www.cleverscope.com/resources/Cleverscope%20oscilloscope%20review.pdf), the input range (FSD) is given as 16mV - 80V with a note: ""Some CS328A systems had a maximum input range of 40V; this has now been put back to 80V."" The user's manual V2.6 says 40mV - 20V. Please explain what is true and why.

2.) In the comparison sheet, the signal generator output is given as +-5V. The data sheet (http://www.cleverscope.com/resources/Cleverscope%20Data%20Sheet) says +-0.1V-5V. Is this still true? Somewhere in the Forum I read that this is now limited to 0.5V-5V (http://www.cleverscope.com/forum/viewtopic.php?id=152). Please explain.

3.) Are there any plans for an improved or changed signal generator, e.g. with +-10V or more output, -20dB and -40dB attenuator, more oomph, and maybe an AFG? When could this be expected and is it user-upgradeable?

4.) The data sheet and some discussion threads (http://www.cleverscope.com/forum/viewtopic.php?pid=381#p381) mention the use of repetitive sampling to improve the timing resolution. The latest user's manual does not mention it anymore. Can you please explain if repetitive sampling is still possible and how to use it?

5.) In the mathematic section, I did not find a function for Offset. In my experience this is very important to manually compensate a slight offset in the data that would otherwise create a large error when integrating the signal. Is it possible to manually compensate the offset in the recorded data and how would one do this?

6.) In 2007, there was some discussion about the internal noise vs. input range (http://www.cleverscope.com/forum/viewtopic.php?pid=309#p309). It also said that you were working on improving this. Can you please post an updated table with the latest CS320A values?

7.) Using two CS820A in parallel - are the signal generators also synchronized (same master clock, adjustable phase shift between both sine waves?)

8.) The ""Link Connector"" has two pins marked ""Dig Out 1"" and ""Dig Out 2"". What can they be used for?

9.) The data sheet says it contains ""A rear panel I/O connector with a 100 Mbit/sec bi-directional LVDS/RS422 link, and three RS422 outputs."" Can the RS-422 link be used to remotely control the CS820A without the need for USB? This would make an integration with Microcontrollers easier.

Thank you for your help!

25 May 2009
Posts: 395

Hello Dat,
Thanks for your questions. As you point out, we have specs in a number of places, and it is time that we made them all the same! Anyway, answers:
1. The input ranges for the CS320/8A is +/-10 mV to +/-20V. The offset system can automatically put the input range anywhere in the range +/-20V (with 1mV resolution below +/-2.5V and 8mV resolution between +/-2.5 and +/-20V). We decided to move from +/-40V (which is used in the CS328 classic) to +/-20V for two reasons. The first was that having a range of +/-40V makes mains accessible to a 1/10x probe (a useful thing you would have thought), but then increases the likelihood that people will use the 1/10x probe for 230VAC mains work. We had a number of people inadvertantly connecting the ground probe to mains with some repair required afterwards (there's a sacrificial ground track under the PCB's to be reconnected), and the possibility that they might damage themselves or their computers. So we decided that it would be better to offer differential probes for use in this situation. We reduce the liklihood of this happening by having a +/-20V range. We also strongly encourage people to use a Residual Current Detector or Ground Fault Interrupter when working with mains. For those who use an RCD, and don't want the cost of a differential probe, we offer the CS1002 100x probe. The CS320/8A front end is protected against mains exposure.
The second advantage of doing this is that it cuts the noise in the upper ranges (+/-5 to +/-20V) in half.
2. It is true that we have used a shorthand notation when saying the amplitude range is +/-5V. The smallest signal we can currently make is about 500 mV p-p. We do agree that it would be good to have a programmable method of reducing this. If we need less we use a 50 ohm attenuator (we have a bunch between 6dB and 30 dB). The passive attenuators are good because they reduce the noise as well as the signal - something an op-amp based attenuator does not do. We did not include programmable attenuators for cost reasons.
3. Yes we are working on an AWG, and it will have greater voltage,frequency and amplitude range. It will be a plug-in replacement for the existing sig gen. We cannot give you a date - our progress is always moderated by other stuff that's happening at the same time.
4. Yes repetitive sampling is built into the standard application (set the Display method to repetitive). Resolution is 0.2ns. The minimum frequency that can be viewed this way is 1 MHz (though this is arbitrary - the data sets just get quite large).
5. There are two ways of doing offset. The first is to enter an offset pair in the Settings/Analog Names and Units dialog. For example to convert the range 12 -> 1045 to 0 -> 1000 you would enter in pairs 12,0 and 1045, 1000. All values displayed would then be normalized. The second way is to use Maths. Say you wanted to integrate a number that needed to be scaled by 0.96805 and offset by 12 (the example above) you would enter:
a*0.96805 + 12 Integral a
into one of the lines in the Maths Equation Builder.
6. We did post an updated table in April 2007. Here it is again:
Here is a table using your values for the Agilent 54622D, our recent measurements for the CS328, and the CS328A, all in mV p-p, over a 10 us period, peak captured. The CS328 and CS328A were randomly selected, measuring the same common ranges:

FSD mV/div 54622D CS328 CS328A
8mV FSD (1 mV/div) - 0.63 1.3 0.96
16 mV FSD (2 mV/div) - 0.63 1.3 0.96
40 mV FSD (5 mV/div) - 0.63 1.5 1.7
80 mV FSD (10mV/div) - 0.9 1.5 1.7
160 mV FSD (20 mV/div) - 1.2 3.5 1.7
400 mV FSD (50 mV/div) - 3 6.0 1.7
800 mV FSD (100 mV/div) - 6 9.6 1.7
1.6V FSD (200 mV/div) - 19 17 4.0
4V FSD (500 mV/div) - 30 28 8.2
8V FSD (1V/div) - 60 99 36
16V FSD (2V/div) - 130 180 70

7. No there is no way to phase synchronize two sig gens.
8. We have done the programming to make them accesible via the Maths Equation Builder. This will be in teh next release. Thus the Maths equation builder can control the Sig Gen, the outputs, and save to file. We also have plans for the dig out connector to be used to stimulate an SPI or I2C system, and to use the link for some expansion modules we are building.
9. We have thought about this. But it is not implemented. We do have a debug port capability using the port as a serial connection, but this is orientated towards humans not microcontrollers.

I hope this helps!
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