Other Articles - May - 2021

How Much Scope Do I Really Need? Part 2

This is part two of the scope comparison series and in this article, you’ll see how the gold-standard Pico 4425, the mid-line Autel MS-408, the less expensive Pico 2204a, and Hantek 6022BE perform while measuring common automotive circuits. The following includes all four scopes measuring ignition primary and secondary, injector amperage and voltage, CAN bus, and transmission line pressure. See the April edition of Gears Magazine for part one where I used these scopes to measure relative compression, in-cylinder pressures, camshaft, and crankshaft signals. But first, to learn what makes some of these scope shine more than the others, I want to compare the software for these four scopes.

Pico has the most impressive software by far and they are constantly updating it to make it even better. As mentioned in part one, you can download the software for free, and when you open the program, you can select “demo mode” and see a simulated waveform, so you can experiment with the settings. Pico has three versions of software; the PicoScope 6 works with all of their scopes; PicoScope 6 Automotive works with their automotive specific scopes; and PicoScope 7 (figure 1) works with their automotive specific scopes and is a completely different look than PicoScope 6 standard or automotive version. I’ve yet to warm up to PicoScope 7, because it seems to be mainly configured for touchscreen computers, which I don’t have. It’s still in Beta version, so expect it to get better and more usable with every release. The strong points regarding Pico’s software include frequent updates, buffered waveforms (collecting screens for post-capture review), powerful math channels (advanced feature), and versatile “custom” probes, where you can make the scope display a custom probe with the proper units, such as pressure. The beauty of Pico is that their powerful software works with their expensive scopes as well as their $130 2204a scope.

Autel software (figure 2) looks very similar to the Pico. It’s not as frequently updated, but it’s simple and functions well. They have software that’s available to integrate with their scan tools, but they also have software available for a Window’s PC, which is what I’m using for the comparison. Like the Pico, Autel’s software buffers the waveforms for post-capture review, allows for math channels and custom probe creation, but it’s definitely not as feature rich as the Pico. Although the for the price of the Autel, and depending on your purpose for the scope, the Autel is hard to beat.

Lastly, the Hantek software, which is really the big negative on this scope. The Hantek software hasn’t been updated in a real long time, and it doesn’t appear as if it ever will. The software is “open-source,” which means a user can create their own software for the Hantek scopes. Some have and there are actually phone apps, like H-scope, that allow you to use your Hantek scope with your phone as the display. It’s actually pretty nice. The OE Hantek software, unfortunately, leaves much to desire. There is no “AC” coupling, so if you need to use AC, you’ll have to do it with a physical AC filter, which is basically a simple capacitor. There are no custom probes. No math channels. Even the way it captures data and displays it is not ideal, because the Hantek software doesn’t buffer screens like Pico and Autel. Now the Hantek I’m comparing here is really the cheapest scope I could find, so we should keep that in perspective. It’s only 60 dollars and as you’ll see, it actually does quite well with most of the tests.

Injector Voltage and Amperage:

Injector voltage and amperage is a common measurement performed with a scope. On a port fuel injection vehicle, the technician can monitor the amperage and actually see the pintle “bump” in the waveform as amperage builds. Amperage ramp and amount will indicate excessive resistance and short circuits. While monitoring the voltage, the tech can see the pintle close by monitoring the pintle “bump” when the voltage spike reduces.

That’s all true with port injection, but these images show a gasoline direction injection (GDI) injector. The patterns are different, because GDI injectors are initially charged with a higher voltage (60+ volts), then held open with a PWM 12 volts. The pattern looks quite a bit different from a port fuel injection injector. The tech can still monitor for proper amperage and adequate voltage. The scopes all did well with injector voltage and amperage. The Pico 4425 (figure 3) and the Autel (figure 4) can handle the voltage without any scope modifications and did an excellent job. The Pico 2204a (figure 5) and the Hantek (figure 6) have a relatively low input voltage capacity. These scopes are limited to 20-volt max input, so the injector voltage would possibly fry the scopes if precautions weren’t taken. To measure voltage higher than 20 volts, the Pico 2204a and Hantek test leads have a 10x setting built into the probes. Using this 10x setting will reduce the voltage going to the scope by 10 times, so the 60-70 volts will get knocked down to 6-7 volts, which makes the scope safe to use with the higher voltage injectors.

Conclusion: The Pico 4425 and Autel make it easy to check injector voltage and amperage without requiring any special precautions when using the scope. The Pico 2204a and Hantek require the use of the 10x setting on the probe or the use of an attenuator to reduce the voltage to the scope since they have low input voltage capacity.

Ignition Primary and Secondary:

Those of you that are old, like me, will likely have experience with ignition scopes. They were the monsters that lived along the wall in a shop. As computers and hardware improved in the 90’s, the digital storage oscilloscopes began to arrive on the scene. Now that scopes are once again a common place, it’s no surprise that technicians are still measuring ignition primary and secondary while diagnosing vehicles. With my test vehicle, the coils had transistors built into the coils, so they had a power input, a ground, and a signal circuit. The signal circuit is just a 5-volt square wave telling the transistor in the coil when to turn on and when to turn off. On this vehicle, the only measurements I could perform is coil amperage and secondary voltage.

The Autel kit come with a secondary ignition clip that is placed on the spark plug wire and the Autel and Pico have a custom probe already installed in their software. The Pico 2204a doesn’t have that probe preinstalled, but you can always download the Pico automotive scope software and “export” the automotive probes from Pico Auto and then “import” the probes into Pico 6, which is the software used with the 2204a. The Hantek doesn’t have the ability to set custom probes, but you can still see the pattern and manually do the conversion if needed.

Conclusion: The Pico 4425 (figure 7) and the Autel (figure 8) worked great at checking secondary voltage and primary current. Their custom probes allowed for an easy setup with very little configuring. The Pico 2204a (figure 9) needs the probe imported, but it works well so long as your time base setting is set for 200ms/500ms/1s per division. The limitation of this scope is that it can only capture at a high rate in these settings. It works fine, but you’ll have to capture your pattern then zoom in to evaluate it. Hey, what do you want for a 130-dollar scope? The Hantek (figure 10) worked well for displaying the secondary ignition ign pattern, but without the custom probe feature, you would have to manually figure out the voltage. It did work well with primary amperage.

Communication Networks:

The most common communication network is the Controller Area Network (CAN). This is a two-wire network that consists of a CAN+ and CAN-. When a message is not being sent, both CAN+ and CAN– are at approximately 2.5 volts. When a signal is being sent, the CAN+ toggles up and CAN- toggles low. These two circuits mirror each other. They are NOT fault tolerant, which means if one signal fails, the whole network goes down. Common DMM tests include checking the resistance between CAN+ and CAN-, which should be 60 ohms and checking for proper idle voltages on the circuits. A multimeter cannot show the actual CAN signal, because it switches so fast. The benefit of a scope is that it can display the actual signal and the tech can see missing signals and patterns that don’t have a proper shape. Some of the scopes can also “decode” the CAN signal and display the “hex” code. All of the scopes did a great job of displaying the CAN bus signals. The Pico 4425 (figure 11), the 2204a (figure 12), and Autel (figure 13) have the capability to decode the signal, but the Hantek (figure 14) does not.

Conclusion: if monitoring the voltage and shape of the CAN bus signals is the priority, all of the scopes will work fine. If you feel the need to decode the signal into its hex decimal, then you’ll want the Pico or the Autel. One final note on networks, Flexray is slowly appearing on the scene and it’s much faster than the CAN. I found that the Pico 4425 and Autel and even the Hantek are fast enough to monitor and properly display the Flexray, but the cheaper 2204a cannot keep up with the speed.

Transmission Pressure:

It’s become popular to check pressures with a scope vs. using a pressure gauge. With a scope you can see how quick pressure responds. If you have multiple pressure taps, you can display and compare multiple pressures in different oil circuits. For example, on a Honda 5 or 6 speed, you can measure and display clutch pressures and see how they overlap. This can give you clues to CPC operation, leaks in clutch circuits, and regulator valve issues. The Pico (figure 15 and 16) was the true winner, mainly because the available options when setting up a custom probe.

If you’ve ever experimented with stand-alone pressure transducers, they aren’t all 1mv equals 1psi. Usually, .5v is equal to 0psi and 4.5 volts is equal to 500psi, for example. This means it’s not a simple 1:1 relationship and zero volts doesn’t always equal zero psi. This is not a problem if the scope software allows the technician to make a custom probe through a table or an equation that will match the characteristics of the probe.

The Pico software allows for such a calculation. The Autel scope (figure 17) allows the user to create custom probes, but it only allows for one option (linear equation y=mx+c), and it auto generates the ranges, which in my experience are not adequate for the pressure transducers we use. I’m hoping that Autel will update their software at some point to improve their custom probe options.

The Hantek isn’t very useful with pressure transducers since it doesn’t allow the creation of custom probes.

Conclusion: The Pico shines with its excellent custom probe menu. The Autel would be just as good if they improved the custom probe options. Hantek wasn’t even worth using since I couldn’t create a custom probe.

There you have it. Are scopes complicated? Yes, but they are only as complicated as you want them to be. They still measure voltage over time and display it on a screen, but you can make them do so much more. Are they expensive? Yes and no. There are expensive scopes that have more features that many will never use, and there are inexpensive options that actually work very well at doing common automotive tasks. If you want more information on how to use these scopes to do some of the mentioned measurements, plan on attending EXPO2021 in Las Vegas this October. I’m doing a presentation on scope usage and I’ll bring all of these scopes with me and we can do some live testing!