B&K Precision 2120B Manuel d'instructions télécharger pdf

HB 08-18-2010 1

Oscilloscope

Equipment SWS, BK Precision model 2120B oscilloscope,Wavetek FG3C function generator,

2-3 foot coax cable with male BNC connectors, 2 voltage sensors

Reading How To Use Science Workshop, pp. 170-183 (scope display). Review the “Voltage,

Current, and Resistance” writeup for the use of the SWS signal generator.

Remark The oscilloscope is a diﬃcult instrument to understand, but it is also a very impor-

tant instrument. Studying this write-up carefully before the lab will be worthwhile. This

lab cannot be approached casually.

1 Introduction

The standard instrument for examining time dependent voltages in a circuit is the oscillo-

scope, or “scope” for short. Even if you are doing a DC experiment it is a good idea to

look at the circuit with a scope. You might ﬁnd a large AC signal symmetric with respect

to ground that does not show up on DC instruments but is aﬀecting your experiment in

undesirable ways, such as overloading a sensitive ampliﬁer. Oscilloscopes are ubiquitous in

the medical profession. They are seen next to hospital beds showing the electrical output of

a heart. They are used extensively in operating rooms.

A voltage which depends on time can be drawn on graph paper with the voltage on the

vertical axis and the time on the horizontal axis. If the voltage is periodic (repeats itself

after one cycle) an oscilloscope will present a similar curve. By adjusting the scope it is

possible to display part of one cycle or many cycles of the waveform. Properties of a periodic

voltage, such as shape, peak-to-peak amplitude and period, can be measured. Is that sine

wave from your signal generator distorted? Feed it into a scope and ﬁnd out. Scopes have

other uses, but these are the primary subjects of this lab.

The oscilloscope is a sophisticated instrument. Competent use depends on understanding

how this instrument works. It is often necessary to consult the instruction manual for a

particular scope in order to use it eﬀectively. The basic ideas are usually the same but are

implemented in diﬀerent ways.

In this lab you will become familiar with 2 oscilloscopes, the model 2120B made by BK

Precision, and the SWS scope. Both these instruments do very much the same thing except

that the controls on the BK are mostly knobs and switches and those on the SWS are icons

and buttons. The SWS scope is digital. The input waveform is digitized and stored, at least

for awhile. The BK scope is analogue. The input voltage may be ampliﬁed, but it is not

digitized and stored.

2 Analogue Oscilloscope Basics

The heart of an analogue scope is a cathode ray tube (CRT). See Fig. 2. A cathode ray is

an historical name for a beam of electrons. The “tube” refers to the glass vacuum envelope.

Electrons are thermally emitted from a hot cathode. They are accelerated (through 2 kV

in the BK scope) by an electrode and then focused into a thin beam by electrostatic lenses.

A vacuum is necessary so that the electrons will not be scattered by air molecules and so

that the cathode will not burn up. The electron beam is then passed through 2 pairs of

1 2 3 4 5 6 ... 15 16

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Page 1 - 1 Introduction

HB 08-18-2010 1OscilloscopeEquipment SWS, BK Precision model 2120B oscilloscope,Wavetek FG3C function generator,2-3 foot coax cable with male BNC conn

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HB 08-18-2010 10up most of the screen and horizontally there is about one cycle of the input waveform on thescreen. Use the calibration of the VOLTS/D

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HB 08-18-2010 11trigger pulses to produce a trace. This corresponds to AUTO for control 32 of the BK scope.A diﬀerence here that that the TRIG button

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HB 08-18-2010 127 Analog versus Digital ScopesIn an analog scope the input voltage, after ampliﬁcation or attenuation, is applied to thevertical deﬂec

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HB 08-18-2010 13The output of the Wavetek function generator can be modulated at 400 Hz by an inter-nally generated sine wave. The modulation can be e

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HB 08-18-2010 14Figure 1:Figure 2:

Page 7 - 5 Using The BK Oscilloscope

HB 08-18-2010 15Figure 3:Figure 4:

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HB 08-18-2010 16Figure 5:

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HB 08-18-2010 2deﬂection plates. A voltage across one pair of deﬂection plates deﬂects the electron beam inthe vertical direction, while a voltage acr

Page 10 - 6 Using The SWS Oscilloscope

HB 08-18-2010 33 Description of How a Scope Displays a Single Periodic VoltageA periodic function in time is one that repeats itself again and again,

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HB 08-18-2010 4We consider the case where the trigger pulse is derived from the input voltage, which is thevoltage that is to be observed. The operato

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HB 08-18-2010 5buttons, connectors, etc. The controls that are used mainly for dual trace or x-y use willnot be discussed other than to adjust them fo

Page 13 - 9 Finishing Up

HB 08-18-2010 61. ON indicator. Lights when scope is on.3. POWER pushbutton. Turns scope on and oﬀ. Leave scope oﬀ (button out).4. INTENSITY control k

Page 14 - Figure 2:

HB 08-18-2010 720. CH2 VARIABLE/PULL control. Adjusts the vertically sensitivity of channel 2 contin-uously.21. CH2 INPUT JACK. Not needed in this lab

Page 15 - Figure 4:

HB 08-18-2010 8helpful to refer to previous sections during these exercises. Reminder: the VOLTS/DIV andTIME/DIV switches are not calibrated unless th

Page 16 - Figure 5:

HB 08-18-2010 91. the VOLTS/DIV controls are changed (15 and 16)?2. the TIME/DIV controls are changed (23 and 26)?3. the trigger level (33) voltage is

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B&K Precision 2120B Manuel d'instructions

Naviguer en ligne ou télécharger Manuel d'instructions pour Générateurs d'électricité B&K Precision 2120B. B&K Precision 2120B Instruction manual Manuel d'utilisatio

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