CEN'l
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Our advertisers are vital to the
success of Silicon Chip . Please
give them your support.
Altronics . .
. 36,37 ,52 ,
53,60 ,61
Arista Electronics ..... .. 64
Australian Geographic
. IBC
Dick Smith Electronics
. .. 18, 19,44,45,65, 75
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12
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15 ($7 .00)
16 ($7.40)
17 ($7.80)
18 ($8.20)
19 ($860)
20 ($9.00)
Elmeasco Instruments . . .. 81
Jaycar Electronics .... 24-32
Marantz Australia . . ... . . IFC
Scan Audio Pty Ltd
. OBC
21 ($9.40)
22 ($9.80)
23 ($10.20)
24 ($10.60)
25 ($11 .00)
PC Boards
26 ($11.40)
27 ($11 .80)
28 ($12 .20)
29 ($12.60)
30 ($13.00)
Name ....... .... ... ........ .... ... .... .... ......... ...... ...... ..... ..
Printed circuit boards for Silicon
Chip projects are made by:
R.C .S. Radio Pty Ltd,
Suburb/Town .. ........ ....... .. .... ..... .. ..... ........ ... ........... ... ..... .. .. Postcode ............... . .
651 Forest Road , Bexley,
NSW 2207 .
Phone (02) 587 3491.
Enclosed is my cheque or money order for $ ..... .. .... ..... .. ...... .... . ....... or pl ease debit my
Bankcard □
Visa □
Jemal Products ,
5 Forge Street, Kewdale , WA
Card No .... ...... .... ........ ....... .......... ...... .... ... ..... .... ... .... .. .... ..... ....... ..... .... ... ... ... .
6105.
Signature ......... ... .... .. ... .. ... .. .... ........ ...... ... ..... ..... ... ..... ... .. ...... ... ... ... .. ... ... .... .
Phone (09) 451 8726/2275 .
······ ··· ··· ······ ····· ··················· ··· ·····
Address ........ ... ....... ........... ..... ..... ............. ..... ...... .. .... ............... .. ......... .. .... ... ..... .. .
Capacitance adaptor for DMMs scissors, then carefully affix it to
the front panel. The front panel can
now be drilled to take the switches
and test terminals.
Alternatively, you can use the
artwork reproduced with this article as a drilling template. The switches and terminals can then be
labelled using Letraset rub-on lettering. Spray the finished panel
with Estapol clear lacquer to stop
the lettering from rubbing off.
Next, mount the switches and
test terminals and complete the
wiring as shown in the diagrams.
The case can now be drilled to accept the board assembly. Two 8mm
holes are drilled in the rear panel to
provide clearance for the banana
plugs, while another three holes are
96
Advertisers Index
SILICON CHIP
ctd from page 23
drilled in the sides of the case to
allow screwdriver access to the
trimpots.
The assembly goes together with
the battery sandwiched between
the board and the case lid (see
photo). Strips of insulation tape can
be used to prevent shorts between
the battery case and the trimpot
wipers.
Calibration
Calibration involves first setting
the null adjustment (VR3), then adjusting VR 1 and VR2 so that the
DMM displays the correct reading
for capacitors of known value on
the LOW and HIGH ranges
respectively.
To set the null control, set the
DMM to the millivolt range, set S2
to LOW, and adjust VR3 for a
reading of 0mV. In practice, it will
be difficult to set VR3 so that the
meter reads exactly zero, and a
reading that is slightly negative will
be satisfactory.
Now connect a capacitor of
known value between 1000 and
2200pF to the test terminals. Adjust
VRl so that the meter displays lmV
per picofarad (eg, if the capacitor
value is l000pF, adjust the meter to
read 1V).
Finally, select the HIGH range
and connect a 0.1-1/.tF capacitor to
the test terminals. Adjust VR2 so
that the meter displays 1V per
microfarad (eg, 0.1V for a 0.1/.tF
capacitor, 1V for a 1/.tF capacitor).