标签: multimeters

My aim is to boost your value in only twenty minutes a day. That is the amount of time that commercials take in a one-hour television program. So instead of advancing forward with the DVR or going to the fridge because that food commercial triggered your hunger to go get a snack, here’s the second best thing you can do besides an abdominal workout or throwing dumb bells around. Bettering your engineering skills involves both the physical circuit evaluation and solving equations. As it turns out, you can probably do both for an investment of under $100. In this world of surface mount, highly integrated silicon, expensive software, and sophisticated test equipment, how can that be? Well, relax folks. I’m a power engineer. I’m expected to achieve 100 percent efficiency at no cost. Of course you’ll settle for high efficiency at some cost. However, I’m a cheap skate when it comes to investing in my business. I look for deals that allow you to build a lab at minimal expense. Solving equations is a great way to improve your value. The time spent designing in most engineering jobs is 5 to 10 percent. Or at least that was my experience at larger corporations. That number increased at startups but not much considering I developed web pages, marketing plans, business plans, etc. With such a little amount of time invested, you can quickly lose your skills. This happened to me when I decided to go back to graduate school after three and a half years in industry. In order to refresh my knowledge, I went down to the college bookstore and bought a book titled Schaum's Outline of Electric Circuits. Nowadays you just look it up on Amazon (Reference 2, 3). They are up to the sixth edition versus the 2nd edition I used 25 years ago when dinosaurs ruled the earth and cars consumed fuel at a rate faster than Seattle-ites consume coffee. As for the physical part of improving your value, life is so unfair. Components have shrunk to the point where us fifty-somethings can't even see the darn things. Further frustrating you is the inability to get a scope probe on the lead let alone hook it with the probe. As a final blow, who wants to spend tens of thousands of dollars outfitting a lab? Fear not my friends; El Cheapo to the rescue. The best way to solve the dilemma of the physical circuit is to invest in the old style plugin breadboard with leaded components. I know what you’re thinking: "Good luck finding one and then purchasing the components individually let alone finding leaded ones." I have a solution. It even has jumper wires so you don’t end up stripping that old Ethernet cable that’s long since been replaced by wireless in your home. That will keep you from scrounging around in the attic like an uninvited chipmunk for the second time. Those of you who suffered the fate in the 1990s are probably grimacing in agony at that memory. My solution for a physical lab platform is in the form of the Radio Shack Electronics Learning Lab (Reference 1). Prior to financial strangulation by divorce and cheaper labor, I intended to get one of these for each of my sons. I would wait for Christmas so that the price would drop from $59 to $49. I was pleasantly surprised to find out that these are currently (as of this writing August 2015) going for only $31 smackers.   These make for excellent hobby kits that will have your kids focusing less on thumb pressing their gizmo and more on the physical world and the holidays are just around the corner. No, Radio Shack doesn’t pay me although I could use a break on last minute components for my prototype. I will say that Mouser, Coilcraft, and Fairchild have been more than responsive for providing fast turnarounds. Perhaps you are thinking, "Big deal getting me a thirty dollar circuit that I have to analyze with a kilobucks scope." As it turns out, there are several smartphone applications such as Oscilloscope Pro (See Reference 6) that turn your phone into an oscilloscope. Perform a Google search and you will find both Android and iPhone applications to suit your needs. Just remember, there are voltage limitations to adhere to unless you wish to fry your phone. Don’t be plugging these into the wall until you understand the allowed input ranges. Like oscilloscopes, digital multimeters (DMMs) have really come down in price. Walmart has DMMs (See Reference 8) for under $10. My suggestion is to get one that has the ability to read current as well as voltage. However you might still have to insert a low value resistor in order to read current with an oscilloscope as current probes are not easily adapted to phone based scope applications. I typically parallel ten 1-ohm resistors to ensure accuracy for measuring current. Here is one final hint for you. Although the Radio Shack Learning Lab is battery powered, you just might need to make yourself a DC power source. Instead of hiring me, buying a demo board, or stretching a long lead from the cigarette lighter in your car; grab yourself a bunch of these jacks (490-PJ-002AH , See Reference 7) that fit the plug on most computer power supplies. Although they are surface mount products, you can solder wires to them or order through-hole versions. In addition to smartphone-based oscilloscope applications, you can find some neat little signal generators too. Some versions have PWM capability. Just remember to turn the sound down as the whole office will glare at you like they did me. The one I used would activate the phone’s speaker if I didn’t have a load plugged into the audio jack. Don’t tell your offspring that these signal generator apps are available as they need to experience the frustration of wiring a 555 timer for themselves. It probably won’t work anyway as they have most likely already downloaded the sig gen app between times when they were getting game cheat codes and overusing the world “like”. By the way, I developed an app that counts that overuse for you!   Scott Deuty