Steve Smith gives some tips and tricks on cleaning up those captured signals, without losing vital information.
Within this article you will discover a number of PicoScope features and techniques that will reveal the signal that lies beneath. In this typical example we are using a narrowband Zirconia lambda sensor.
Both the test procedure to capture this waveform, and the expected result from the capture of such a component has been well documented in the past. With its characteristic sine waveform switching from 0.1 V to 0.9 V at a frequency of 1 Hz.
What is not so documented is the vulnerability of such a signal in the harsh environment of the engine bay, with high frequency switching components radiating EMI (Electromagnetic Interference). The image above presents a typical example of noise induced into a lambda sensor signal, seen here as long rising / falling spikes and hash about the sine wave that lies beneath.
The tool used to capture the lambda sensor signal will determine just how much of this noise is visible. There are tools available which will present a textbook artificially conditioned signal to the technician, so revealing only half the story.
Could the noise actually be responsible for a lambda sensor code or an emission failure? Within the noise itself could be evidence of ignition/injection spikes, arcing from worn components, chafing to adjacent cables or shorting internally to the lambda sensor heater element / engine ground.
Without the true signal revealed on screen how will we ever know?
Over the last few months, we have been placing new content on our PicoScope Automotive YouTube channel. These videos are short informative clips giving an overview on how to connect certain accessories to a vehicle, and how to complete the associated test.
Below are a couple of examples of our new videos:
Please click the button below view the PicoScope Automotive YouTube channel. We will be adding new videos to our channel on a regular basis, so why not subscribe to our channel and you'll receive updates when new videos are posted? In addition to this, you can also submit videos to us you feel would suit our best of the web section.
Last month we gave a reminder about our Scope School articles. Following on from "Scope School 2: The next step" last month, Steve Smith now moves on to "Scope School 3: Tips and Tricks"
While we never stop learning in this ever-evolving trade of ours, we have to bring Scope School to a close. So I want to finish off by talking about some of the tips and tricks of PicoScope that can make life easier as you develop with this essential tool. In this final chapter I'll cover some capture and analysis features that I am sure you will find invaluable during your diagnosis.
The Coupling option is located next to the voltage range control. The default DC setting allows the scope to display both the DC and AC aspects of the input signal. Selecting the AC coupling option we block the DC component of the input signal and allow only the AC to be displayed on screen.
As an example of the value of this feature, connect Channels A and B of your scope across a 12 V battery and start the engine (enabling the alternator to commence charging). Leave the coupling option of Channel A set to DC (120 V) and select AC coupling for Channel B (1500 mV). Channel A will display the DC voltage, and Channel B will display the AC voltage across the battery revealing the alternator ripple. We are measuring the same voltage but gaining the value of two properties from it. Applying this coupling feature to fuel rail pressure sensors and certain active wheel speed sensors will reveal much more.
There may be times during scope use where you miss the event you were trying to capture. This could be a momentary misfire or drop in signal while wiggle testing a wiring harness. Stopping the capture and using the buffer feature enables you to scroll back through time, a screen at a time. PicoScope stores the last 32 screen captures (or more, depending on scope settings), allowing you to scroll through your data to find and view the waveform with the misfire or signal dropout; this is the proof needed for you and your customer.
Reference waveforms are a great way to help you compare a known good waveform against your captured suspect waveform, on the same screen. With your known good waveform on screen, select Tools > Reference Waveforms and then select the waveform channel of interest from the Available list. Now click the Duplicate button and tick the box adjacent to your highlighted waveform in the Library list, then click OK.
A duplicate of your known good waveform will appear (and remain) on screen while you capture a suspect waveform for comparison.
It's time for another competition, and it is quite possibly our biggest giveaway ever...
|To support our new product Review system we are asking you to tell us what you think of our products.|
|If you've bought one of our products (either direct from us or through one of our distributors) please find it on our website, look for our new Review button (as seen above) and leave us your feedback. Note that to leave feedback we must have your email address, this allows us to contact you regarding your review and in this case, contact you about your prize if you are lucky enough to be a winner.
What prizes are on offer you ask? 9 reviews will be picked at random with prizes as follows:
In total we have 9 prizes to give away, so what are you waiting for? Head over and leave us your first review! There is no limit to the number of reviews you can leave, so why wait? If you have bought a kit from us, we are more than happy for you to leave a review for each piece of equipment within the kit that appears on our site. Each review will count as an entry to the competition. More reviews, means more entries, which means more chances to win.
Terms and Conditions
All reviews left are checked by Pico Technology, and those that are deemed to be authentic will be entered into the competition. Entries must be received by close of business (GMT) on 15th April 2016. Winners will be contacted before the end of April 2016.
Following the recent software and hardware updates to our PicoDiagnostics NVH kit, we are now offering a route for owners of the PP858 PicoDiagnostics NVH kit to upgrade their Pico NVH hardware.
The new hardware allows you to take full advantage of our latest version of PicoDiagnostics NVH software, which supports analysis of up to four vibrations or sounds simultaneously.
The upgrade kit contains the 3-output interface box and three coloured BNC cables all of which are compatible with your existing TA143 accelerometer.
Please visit Pico Exhibitions for the latest list of exhibitions and trade shows that Pico and its representatives will be attending.
Thanks to our continuing success and growth Pico are always seeking talented people to join our company.
Please visit http://pico.jobs/ to see our current vacancies. We look forward to hearing from you!
Our latest software releases are available as free downloads. To check which release you are using, start the software and select Help > About.
To make sure that your Pico newsletter reaches your inbox every month, add email@example.com to your email address book or safe list. If you found this newsletter useful, please recommend it to your friends and colleagues. Back issues are available from our newsletter archive.
Pico Technology, James House, Colmworth Business Park, St. Neots, Cambridgeshire, PE19 8YP, England
Tel.: 01480 396395 (+44 1480 396395)
Fax: 01480 396296 (+44 1480 396296)
Pico Technology North America Inc.
320 N Glenwood Blvd.
Tel:+1 800 591 2796 (Toll Free)
Fax:+1 620 272 0981
Web technical support: www.picotech.com/tech-support/