I was messing with a common rail Audi Q7 the other day & I was studying the pressure regulation function on the two solenoids & the duty measurement on screen was really messing with my head whilst I tried to comprehend the processes in real time. I got there in the end, but it was harder work than it needed to be & even harder work trying to explain it to those who I was trying to bring up to speed on the subject. It was kind of like trying to explain to a child that when the big hand points to the three, that this means 15 minutes past or a quarter of an hour (you get the idea)
Dave Allen - "Teaching Your Kid Time"
Come on Pico team ..... please please please, can we have options for duty high & low measurements, preferably before I am in an old folks home.
Merry Christmas everyone!
Martyn wrote:Until we add in this option, you can always create an inverted maths channel and measure the duty cycle of that
Running math live is not a best option.
In automotive most signals are low type so I agree with Dave Hill that it's time to get it implemented.
liviu2004 wrote:Please Pico don’t make a digital meter out of a scope. I want the scope to be a scope, if I want to measure a value, I have a Fluke in my trunk, who hasn’t and still works in automotive?
Why should one use two tools at the same time if there is possibility to use only one?
Is there any possibility for the following feature;
When measuring CAN bus signals (or any other bus for that matter) with serial decoding turned on, any error frames are recorded in the table below in Red.
Is it possible to add a feature whereby the scope beeps when a frame error occurs. I see this could be a very useful feature for assisting with intermittent wiring faults on the CAN Bus. Particularly when its not possible to observe the scope when disturbing a wiring loom, for example when driving.
Afterwards we could then export the list of frames recorded with errors, and compare their frame ID's with the manufacturers bus matrix to determine to section of the bus with potential faults.
Traditionally I set the oscilloscope up in the following manner to check for CAN faults;
Channel A - CAN Hi
Channel B - CAN Lo
Math channel calculating Ch A + B ( = 5V)
Add a mask on the math channel with +- 1V tolerance.
Then as soon as there is any short to ground/positive or a mirror failure on the bus, the scope records this event and beeps.
However to use the math channel, mask and serial decoding at the same time requires quite a lot of processing power.
Therefore I would like to know if we can set the scope to beep purely on the basis of a detected frame error.
Really appreciate if this feature can be implemented.
Well, you are in luck! This feature already exists within PicoScope and can do exactly what you ask. If you have set up your Maths channel with a mask, you can ask the software to do a number of things when the trace falls onto the mask.
The current options you have are Beep, Play Sound, Stop Capture, Restart Capture, Run Executable, Save Current Buffer, Save All Buffers and Trigger Signal Generator. The only one we can't use with our Automotive Scopes is the Signal Generator but all the others will work as expected. One that might be useful for the work you are looking to do would be the Save Current Buffer or Save All Buffers. This will store the capture every time the mask detects a failure whether that is the buffer that the mask failed on or all of them. You do need to be aware though that if the scope is left to run and the mask failure is high, you will get a lot of files and will slowly fill up your computer! To activate Alarms click Tools > Alarms. Now you would need to click the drop down arrow to highlight and tick the box for Mask(s) Fail. Now click Apply. From here we now need to tell the software what we would like it to do if there is a mask failure. If you now click Add this will bring up the options I spoke of earlier. If you would like to save buffers then you will need to setup a location to save the captures and then a name for the file. Every time a file is saved the title will stay the same but you will notice a numerical value at the end of the name which increases with every file created. Once you have made your selection click OK and on the list make sure the box is ticked and then click Apply and then OK. You are now ready to start capturing.
Choosing the save option you will now have all the mask fails captured and then you can apply post capture analysis, such as serial decoding. I tend to prefer looking at the decoded data away from the vehicle and not applying it live. As you said it takes a lot of processing power from your computer and there aren’t the distractions we are all faced with when working by the vehicle in the workshop. Plus that way there is no danger of saving over files by accident.
I hope this helps and there are number of helpful files on the forum starting with this one Triggering on CAN with Masks - topic12871.html. You will also find some more information on Serial Decoding within the Mazda 3 case study which you can find here https://www.picoauto.com/library/case-s ... ions-fault where we demonstrate the techniques with Masks and Alarms to diagnose the fault.
There’s a lot of information here but if you need any further assistance please don’t hesitate to get in touch.