Don't know how to use them, are intimidated by their apparent complexity. 101 Ways to Use Your Oscilloscope, Robert Middleton, Sams, 1966 (mainly. Build your own oscilloscope probes for power measurements (part 1) Martin Brown-August 04, 2017. Save to My Library. For those signals below the maximum input voltage rating of the oscilloscope input, you can use a cut length of a 50 Ω BNC coax cable as your probe. PRINT PDF EMAIL. Next: Noise considerations.

Need for speed underground 2 pc save game. Most oscilloscopes can only directly measure voltage, not current. One way to measure AC current with an oscilloscope is to measure the voltage dropped across a shunt resistor.

Since the voltage dropped across a resistor is proportional to the current through that resistor, whatever wave-shape the current is will be translated into a voltage drop with the exact same wave-shape. However, one must be very careful when connecting an oscilloscope to any part of a grounded system, as many electric power systems are. Note what happens here when a technician attempts to connect the oscilloscope across a shunt resistor located on the “hot” side of a grounded 120 VAC motor circuit: Here, the reference lead of the oscilloscope (the small alligator clip, not the sharp-tipped probe) creates a short-circuit in the power system. Explain why this happens.

Most oscilloscopes have at least two vertical inputs, used to display more than one waveform simultaneously: While this feature is extremely useful, one must be careful in connecting two sources of AC voltage to an oscilloscope. Since the “reference” or “ground” clips of each probe are electrically common with the oscilloscope’s metal chassis, they are electrically common with each other as well. Explain what sort of problem would be caused by connecting a dual-trace oscilloscope to a circuit in the following manner. Notes: Failing to consider that the “ground” leads on all probes are common to each other (as well as common to the safety ground conductor of the line power system) is a very common mistake among students first learning how to use oscilloscopes.

Hopefully, discussing scenarios such as this will help students avoid this problem in their labwork. Note to Socratic Electronics developers: the oscilloscope shown in figure 01821x01.eps is made up of individual lines, circles, text elements, etc., rather than a single object as is contained in the Xcircuit library file ( scope.lps). If you wish to edit the features of this scope, start with the 01821x01.eps image file rather than the library object!

Then you may save your modified oscilloscope as a complete object in your own image library for future use. Shunt resistors are low-value, precision resistors used as current-measuring elements in high-current circuits. The idea is to measure the voltage dropped across this precision resistance and use Ohm’s Law (I = V/ R) to infer the amount of current in the circuit: Since the schematic shows a shunt resistor being used to measure current in an AC circuit, it would be equally appropriate to use an oscilloscope instead of a voltmeter to measure the voltage drop produced by the shunt. However, we must be careful in connecting the oscilloscope to the shunt because of the inherent ground reference of the oscilloscope’s metal case and probe assembly. Explain why connecting an oscilloscope to the shunt as shown in this second diagram would be a bad idea.

Notes: The ground-referenced clip on an oscilloscope probe is a constant source of potential trouble for those who do not fully understand it! Even in scenarios where there is little or no potential for equipment damage, placing an earth ground reference on a circuit via the probe clip can make for very strange circuit behavior and erroneous measurements.

Problems like this frequently occur when new students attempt to connect their oscilloscopes to circuits powered by signal generators whose outputs are also earth-ground referenced. In response to the follow-up question, the most obvious answer is to reverse the probe connections: ground clip on the left-hand terminal and probe tip on the right-hand terminal. However, even this might not be the best idea, since it creates a “ground loop” between the oscilloscope and the ground connection at the AC source: Ground loops are to be avoided in measurement circuits because they may be the source of some very strange effects, including the coupling of noise voltage from entirely unrelated circuits to the one being measured.