e005066.pdf

ELECTRONICS SOFTWARE

PC-hosted test equipments

Oscilloscope, generator and frequency counter

If you are occasionally involved in electronics, you’ll know that for most

experiments and repairs you won’t get very far without the required test

equipment. Luckily, a portion of the equipment doesn’t have to be physically

present any longer, since that task can be taken over by a computer.

A technician carrying out a practical experi-

ment as part of his job or hobby always

requires a number of test instruments to

observe the effects of any adjustments. You

soon build up a pile of equipment, like a func-

tion generator, power supply, multimeter and

oscilloscope. It is not worth the effort and

expense to acquire all those expensive instru-

ments if they are only to be used occasionally.

With the aid of the correct software, any PC

with a soundcard can take over many of the

tasks of the instruments just mentioned, as

long as it involves fairly low frequency sig-

nals (up to about 20kHz). Extra hardware is

absolutely not required.

There are a number of companies that pro-

duce software that can be used for measure-

ments and reproduction of signals via the

sound card. What we propose has the bene-

ﬁt of zero expenditure and excellent results.

The Dutchman Marcel Veldhuijzen wrote a

few years ago a number of programs for mea-

surement with a PC, an oscilloscope (Scope),

a signal generator (Sinewave) and a fre-

quency counter (Counter), that can be down-

loaded free of charge from the Internet. We

are talking here about real ‘freeware’, fully

functional programs without any restrictions.

After running the Scope program, you are

confronted with the fascia of an oscilloscope

on your monitor screen, complete with all the

dials and switches. Because the hardware on

the soundcard is used, the sampling fre-

quency is limited to 44 or 48 kHz. But for the

most elementary measurements this is more

than enough. The user can ‘turn’ the knobs

with the aid of the mouse pointer. Besides the

regular adjustments like sensitivity, frequency

and trigger level, there are also knobs for

Elektor Electronics

5/2000

ELECTRONICS SOFTWARE

focus and brightness. They aren’t

really necessary, but it creates the

impression of a real test equipment.

The sampled signal can be ﬁxed and

copied to the clipboard, with or with-

out raster. There are separate adjust-

ments for the sampling time and

duration.

The frequency meter is espe-

cially simple to set up. There are only

two dials present for selection of

measuring time (timer) and trigger

level. There are a further eight push-

buttons to set up the hysteresis.

Even here we see another trick:

there is a knob to stop the measure-

ment. If you do that, the brightness

of the ‘display’ is reduced. The high-

est measurable frequency is decided

by the maximum sampling frequency

of the sound card.

The signal generator , Sinewave,

has also acquired the ‘look and feel’

of a real measuring equipment. Here

the operator can set up the fre-

quency range with the aid of four

pushbuttons, after which the exact

output frequency can be set with a

rotary dial or two pushbuttons. A

separate knob is available for

adjusting the output level, sup-

ported by a mute switch. A separate

sweep section makes it possible to

produce a sweep with the genera-

tor, and two rotary knobs allow for

the selection of the top and bottom

frequency swing with respect to the

centre frequency. The nicety of such

a PC-hosted signal generator is the

accuracy with which the frequen-

cies are reproduced. If for instance

you select 488 Hz on the display, you

also get a true output at this fre-

quency. Try that with the dial on a

real generator…

The three instruments are highly

recommended to any technician

with a PC.

The files can be found on the

Internet at:

They can also be found on the recently

released CD-ROM ‘Freeware & Shareware

2000’ from Elektor.

http://w3.pca.net/~cpclark/

SBTESTEQU.html

(000049-1)

text (Dutch orginal): Harry Baggen

C ONSTRUCTION GUIDELINES

Elektor Electronics (Publishing) does not provide parts and components

other than PCB s, fornt panel foils and software on diskette or IC (not nec-

essarily for all projects). Components are usually available form a number

of retailers – see the adverts in the magazine.

ponents in the correct position? Has correct polarity been observed? Have

the powerlines been reversed? Are all solder joints sound? Have any wire

bridges been forgotten?

If voltage levels have been given on the circuit diagram, do those mea-

sured on the board match them – note that deviations up to ±10% from

the specified values are acceptable.

Large and small values of components are indicated by means of one of

the following prefixes :

Possible corrections to published projects are published from time to time

in this magazine. Also, the readers letters column often contains useful

comments/additions to the published projects.

E (exa) = 10 18

a (atto) = 10 –18

P (peta) = 10 15

f (femto) = 10 –15

T (tera) = 10 12

p (pico) = 10 –12

The value of a resistor is indicated by a colour code as follows.

G (giga) = 10 9

n (nano) = 10 –9

M (mega) = 10 6

µ (micro) = 10 –6

k (kilo) = 10 3

m (milli) = 10 –3

h (hecto) = 10 2

c (centi) = 10 –2

da (deca) = 10 1

d (deci) = 10 –1

In some circuit diagrams, to avoid confusion, but contrary to IEC and BS

recommandations, the value of components is given by substituting the rel-

evant prefix for the decimal point. For example,

3k9 = 3.9 k

Ω

4µ7 = 4.7 µF

color

1st digit

2nd digit

mult. factor

tolerance

Unless otherwise indicated, the tolerance of resistors is ±5% and their rat-

ing is 1 ⁄ 3 – 1 ⁄ 2 watt. The working voltage of capacitors is

black

–

≥

50 V.

brown

10 1

red

10 2

orange

10 3

–

In populating a PCB , always start with the smallest passive components,

that is, wire bridges, resistors and small capacitors; and then IC sockets,

relays, electrolytic and other large capacitors, and connectors. Vulnerable

semiconductors and ICS should be done last.

yellow

10 4

–

green

10 5

0,5%

blue

10 6

–

violet

–

grey

–

Soldering. Use a 15–30 W soldering iron with a fine tip and tin with a resin

core (60/40) Insert the terminals of components in the board, bend them

slightly, cut them short, and solder: wait 1–2 seconds for the tin to flow

smoothly and remove the iron. Do not overheat, particularly when solder-

ing ICS and semiconductors. Unsoldering is best done with a suction iron

or special unsoldering braid.

white

–

gold

–

10 –1

silver

–

10 –2

10%

none

–

20%

Examples:

brown-red-brown-gold = 120

Ω,

Faultfinding. If the circuit does not work, carefully compare the populated

board with the published component layout and parts list. Are all the com-

yellow-violet-orange-gold = 47 k

Ω,

5/2000

Elektor Electronics

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