EC-8.1 The Instruments on the Bench
You can pick up a multimeter, an oscilloscope, a function generator, a bench supply or a logic analyser, set it up for the reading you want, and say what that instrument is doing to the circuit while it reads.
Before:S4-5. Probability Theory & Stochastic ProcessesPE2-4. Sensing Techniques and Sensor SystemsEC-1. Circuit AnalysisUnlocks:EC-13. Laboratory Practice, in Sequence
Almost every laboratory in this area opens with an instrument already set up and a reading already on the screen. That hides the two things that go wrong most often: the instrument was configured for a different measurement, and connecting it changed the circuit. Meeting the five instruments once, on their own, means the later modules can talk about a result rather than about which knob to turn.
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The digital multimeter, and what it is really doing
A multimeter measures voltage directly and everything else indirectly. Current is found from the voltage across a small internal resistor, and resistance from the voltage a known current produces, which is why the three ranges behave so differently.
NPTEL: Electrical Measurement and Electronic Instruments (IIT Kharagpur) · CourseThe oscilloscope: timebase, trigger and vertical scale
Three settings decide whether you see anything at all. The vertical scale sets how much of the screen a volt uses, the timebase sets how much time the width represents, and the trigger decides which moment sits in the middle.
NPTEL: Measurement and Instrumentation (IIT Guwahati) · CourseProbes, and why a probe changes the circuit
A probe adds capacitance and resistance to whatever it touches. A ten-to-one probe adds less of both and costs you signal, and an uncompensated probe distorts every edge it shows you, which is why compensation is the first thing to set.
NPTEL: Measurement and Instrumentation (IIT Guwahati) · CourseThe function generator, and the output impedance nobody mentions
A generator that reads five volts on its display is usually assuming a fifty-ohm load. Connect it to a high-impedance input instead and you get ten, which accounts for a great many measurements that are wrong by exactly a factor of two.
NPTEL: Electrical Measurement and Electronic Instruments (IIT Kharagpur) · CourseThe bench power supply, and current limiting
A bench supply has two settings and gives you whichever it reaches first. Setting the current limit low before powering a new circuit turns a destroyed part into a supply that quietly refuses to deliver more.
NPTEL: Measurement and Instrumentation (IIT Guwahati) · CourseThe logic analyser, and when it is the right instrument
A logic analyser records many lines at once but only as high or low. It is the right instrument when the question is about timing between signals, and the wrong one when the question is about the shape of an edge.
NPTEL: Electrical Measurement and Electronic Instruments (IIT Kharagpur) · Course
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