| Next to a good scan tool, I think having a good | | | | used to measure pressure, vacuum, and current |
| scope is vital to diagnosing today's cars. A scan | | | | with the right accessories. These abilities allow a |
| tool will tell you what the control module is | | | | good scope user to perform engine diagnostics |
| "seeing", but a scope will tell you if the module is | | | | faster and easier. Imagine, for example, testing |
| being told the truth by allowing you to see the | | | | the mechanical health of a modern transverse V6 |
| actual input from the sensors. | | | | in a matter of minutes, rather than hours! |
| The scope you choose should be in line with your | | | | HandHeld Scopes |
| needs and your budget. There are a variety to | | | | Handheld scopes are more convenient than most |
| choose from, but they generally fall into 2 | | | | PC-based scopes and often more user friendly, |
| categories: handheld, or PC-based. | | | | with built in databases and testing methods. The |
| Let's take a look at the two. | | | | Vantage PRO, by Snap-On, is probably the most |
| What Is A Scope? | | | | popular and most capable of the handheld |
| When measuring voltage, there are three tools | | | | offerings out there. Cost, however, may be a |
| that immediately come to mind. The first is the | | | | factor for most, with the PRO 2-channel costing |
| Digital Volt-Ohm Meter, or DVOM. This tool simply | | | | more than many PC-based 4-channel units. The |
| measures voltage and displays it on the screen. | | | | key is in how much help you really need...Do you |
| Most have a variety of features that allow you to | | | | want all the "bells and whistles"? |
| record minimum and maximum readings as well, | | | | If cost is the primary factor, then the UEI scope |
| and certainly they have their place in diagnosing | | | | scan tool may be the choice for you. Having |
| electrical problems. | | | | experience with the original UEI ADL7100 scope (I |
| The next tool is a Graphing DVOM. This tool now | | | | still have it!), I think most beginning scope users |
| allows the measurement to be plotted on a graph | | | | will find this scope more than sufficient for most |
| over time, allowing the user to see the variances | | | | testing needs. |
| in the signal as they occur. | | | | If it's real diagnostic power you want, though, |
| Last is the DSO, or Digital Storage Oscilloscope. | | | | then PC is the way to go |
| The DSO, too, graphs the voltage signal over | | | | PC-based Scopes |
| time. The BIG difference between all three is the | | | | There are PC and PDA scope options available |
| rate that each samples and records these signals. | | | | today, and all offer more power for diagnostics |
| Let me back up a bit. Each tool "samples" the | | | | than the conventional handhelds. The ability to |
| signal and then plots the average to the display | | | | utilize higher sample rates, view on a larger |
| screen...whether in a numerical value or as a graph. | | | | screen, and store/record more information allows |
| The accuracy of the reading is impacted, | | | | the user to find those elusive "glitches" that a |
| therefore, by how many samples per second the | | | | handheld may miss. |
| tool records and averages. The more samples | | | | PICO scopes are at the forefront of automotive |
| taken, the more accurate the reading. Of course, | | | | PC-based scopes, and are competitively priced to |
| there are variances inherent in each tool as well | | | | handhelds. Unlike the databases in most handhelds, |
| that need be taken into consideration. The typical | | | | updates for the PICO are free. Because of their |
| DVOM may sample at the rate of 200-400 | | | | early relationship with Tom Roberts, PICO has |
| samples per second, as compared to a good DSO | | | | become the top choice of techs looking for PC |
| with a sample rate of 20 MILLION samples per | | | | scope applications. |
| second. | | | | There are also other choices in PC scope |
| Now consider the speed at which some input | | | | software/hardware, and I encourage you to do |
| signals occur. As a reference, the typical spark | | | | your homework when comparing. Remember, |
| plug takes 1.5 milliseconds to "fire", and we've all | | | | tools are an investment in your productivity and |
| seen a spark jump it's gap. The graphing meter or | | | | their cost should be compared versus their |
| DVOM just can't sample fast enough to catch | | | | benefits. Keep in mind, too, that any scope is only |
| imperfections in signals operating at this kind of | | | | as good as the user. Make sure the tool you |
| speed. And that is just one area where a scope | | | | choose...and the company you choose to purchase |
| shines! | | | | it from...will be there to help you learn how to get |
| In addition to measuring voltage, a scope can be | | | | the most out of your new scope! |