Hello Group,
Thought I would share an experience I had with the EASE demo software and the support system.
After using it, I emailed EASE with questions I had about it on 4-26-04. Many weeks went by and I hadn’t heard back from them. Someone posted interest in this on iATN and I replied. Here is the thread.
http://members.iatn.net/forums/read.plex?f=forum8&m=36149 That was 5-23-04. I received an email shortly after this stating that, “I understand your having a problem”. On the day of 5-26-04 my questions had answers to them.
These were my questions;
In the demo, the trace seamlessly scrolls across the screen as one might see in a chart record mode or like an analog scope. Is it possible to have this type of display when requesting 32,000 samples per scope trace? Is the "Glitch Capture" for real, or is it just sampling at the maximum speed? Can you adjust the sampling rate? While in the recording playback mode, is this a seamless recording with no gaps in data, or an automated page up/page down feature? Is it possible for a driver to access two ADC's at the same time for 4 channel capabilities? In otherwords, will they be in sync? Can the software run the faster scopes?
EASE wrote;
These are all good and valid questions...
Here is my best shot at answering them:
The sampling rate is a function of the time base selected. The larger the time base the smaller the sampling rate (samples per second). The scope hardware has a limited amount of memory. So if it is gathering data for a longer period of time then it cannot gather that data as fast as it can because the memory in the hw would overflow. So what we did is maximize the sampling rate based on the time base without causing a memory overflow, this is done automatically. It is always better to have the best resolution, so it makes sense to optimize for such.
Glitch capture is defined based on who you talk to. I've found a number of ways to do glitch capture by looking at different scopes, they are not all the same. Some take the min & max per frame at the highest sampling rate. Others actually have circuitry in the hardware that will detect a glitch by filtering out a certain band in the signal. The scope hw we use does not have this circuitry so we sample at the fastest rate gathering min & max per frame & displaying them. If their is a glitch it will show up as a positive or negative spike.
Scopes grab a frame of data based on the Time base set and displays it then grabs the next and displays it. If a trigger is set this will grab the data from the pre or post trigger event. So it is not a continuous stream of data if a trigger is set. If it is not set then the scope will grab data as fast as possible. Their is a marriage between the HW and PC so the PC speed will effect this behavior. So during a recording each tick on the position scroll bar is a frame of data. If something occurs in the signal when the scope hw is not looking it will not grab that data, this is the nature of sampling and it will never be an exact representation of the signal, all scopes behave this way. The faster the sampling rate the closer to the actual signal you can get, however, you must also factor in HW memory because you can only get so many sample points before the HW has to stop and send the data on. This is also a behavior of all scopes.
We have many Automotive scope instructors using our scope for their classes and they also own their own repair shops. They have had no problems with the data being missed. If the scope is used correctly the desired data will be captured.
The driver supports multiple hw devices. However, their is no parallel processing going on here, so the signals are not exactly in sync but pretty close. We make requests for data per HW one after the other, let the HW do its thing then service the data as fast as possible, so you see it may be a function of the PC speed since the data needs to be processed too.
We are currently working on a new release of the scope that will support the 50MHz HW scope, improve on Glitch capture, some bug fixes, add a few more library configuration for some other components in vehicles, and more.
EASE Rep
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Notice how it is mentioned that no parallel processing is occurring and the signals won’t be in sync. This is in reference to a 4 ch scope. My take on this is that if the signals aren’t in sync, this is not a true 4 ch scope and it would be of no use to us.
Nothing has been mentioned about adjustable sample rate request. Glitch capture strategy is mentioned at sampling at the fastest rate. PicoScope is always doing this if we request 32,000 samples. Possibly an unknown sales pitch. This shouldn’t be called glitch capture.
It sort of also makes me wonder how instructors and repair shop owners using this software are not having any problems missing data at low sampling speeds when I know I miss data when this puppy is cranked up! What ever.
I like being able to move two cursors at the same time with the EASE software. Something else that seems sort of neat is placing notation anywhere on the screen. The control panel is very user unfriendly. And why are there goofy imitation knobs that simulate controls on an analog scope?
Interesting how a 50MHz DSO is now in the works isn’t it?
That’s enough for now. Just reporting facts and observations.