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G8MNY > TECH 30.03.26 09:04l 77 Lines 3153 Bytes #60 (0) @ WW
BID : 55823_GB7CIP
Subj: Volt Indicator Screwdriver
Path: ED1ZAC<ED1ZAC<GB7CIP
Sent: 260330/0643Z @:GB7CIP.#32.GBR.EURO #:55823 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Updated Aug 07)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
This is the circuit of a œ1 screwdriver voltage tester...
ROLSTON's ORIGINAL VOLTMETER SCREWDRIVER
If you have not seen one of these, they have a small LCD panel in the flattened
black handle.
_________________________________
/ ~~~---...___
³ -- -- ÚÄÄÄÄÄÄÄÄÄÄ¿ __ ~~~---...
³ |()|<³ |()|<³ ³ ³ ( ) ÃÄÄÄÄÄ¿
³ -- -- ÀÄÄÄÄÄÄÄÄÄÄÙ ~~ ___...--Ù~~~~~~
\ ___...---~~~
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
CIRCUIT
______________________________________
³com L C D ³
³ 220V 110V 55V 36V 12V ~ ³
DIRECT À-Â-----Â-----Â-----Â-----Â-----Â----Â-Ù<- Conductive Mats
TEST ³ ³ ³ ³ ³ ³ ³
ÛÛÄ22MÄÄ22MÄÁÄM92ÄÁÄM91ÄÁÄ1M2ÄÁÄ2M7ÄÁÄ10MÄÁÄÄÄÄ)ÄÄÄÄÄÂÄ=======>SCREWDRIVER
³ NEON
ÛÛÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄ2M7ÄÙ
INDUCTIVE
BREAK TEST
DIRECT TEST
When you touch this button (earth) and prod the testing voltage, it indicates
if the voltage is greater than the displayed graphics. This occurs when any of
the LCD sections sees greater than about 1V. As the LCD current required for
any of the display sections is only the odd pA very high value resistors can be
used to make up the multiplier chain. This means the return circuit can safely
be made though ones finger to earth.
INDUCTIVE BREAK TEST
A neon is also fitted for a Inductive Break-point Test. (what ever that is? To
do with Fluorecent lamps?) It lights when voltages are above 80V, above 2V you
just see the ~ symbol on the LCD.
N.B. with this circuit, this test is not too safe, as current COULD flow
through the LCD to you! So I don't recommended you use the neon option as a
mains tester!
G8MNY's MODIFIED VERSION
To open the unit to improve the calibration and safety etc, pop out the back
panel cover and ...
1/ Change one of the 22M to a 10M (100V) to increase the sensitivity on DC.
2/ Then add a 270pF (20v) cap to reduce the sensitivity on AC.
3/ Add a 220k (250V) into the inductive break test circuit.
______________________________________
³com L C D ³
³ 220V 110V 55V 36V 12V ~ ³
DIRECT À-Â-----Â-----Â-----Â-----Â-----Â----Â-Ù<- Conductive Mat
TEST ³ ³ ³ ³ ³ ³ ³
ÛÛÄ22MÄÄ10MÄÂÁÄM92ÄÁÄM91ÄÁÄ1M2ÄÁÄ2M7ÄÁÄ10MÄÁÂÄÄÄ)ÄÄÄÄÄÂÄ=======>SCREWDRIVER
ÀÄÄÄÄÄÄÄÄÄÄÄÄ´ÃÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ ³ NEON
270pF ³ ³
ÛÛÄÄÄÄÄÄÄÄÄ220kÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄ2M7ÄÙ
INDUCTIVE
BREAK TEST
Now test, and you should find the accuracy better and from DC-50Hz. And there
is no danger of electrocution if the neon indicator is used on Mains.
Why Don't U send an interesting bul?
73 De John G8MNY @ GB7CIP
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