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YT7MPB > TECH 05.01.23 17:06l 173 Lines 7565 Bytes #999 (0) @ WW
BID : 57364_YT7MPB
Read: GUEST
Subj: Re: Lafayete 57 Range Multimeter
Path: IW8PGT<I3XTY<I0OJJ<N6RME<YT7MPB
Sent: 230105/1503Z 57364@YT7MPB.#NSD.SRB.EU LinBPQ6.0.23
On Sun, 25 Dec 22 08:41:00 Z
G8MNY wrote:
> R:221225/0845Z @:N6RME.#NCA.CA.USA.NOAM #:3328 [El Dorado]
> $:36638_GB7CIP R:221225/0842Z @:CX2SA.SAL.URY.SOAM #:20750 [Salto]
> FBB7.00e $:36638_GB7CIP R:221225/0842Z 47561@N9PMO.#SEWI.WI.USA.NOAM
> BPQ6.0.23 R:221225/0842Z 39678@GB7YEW.#79.GBR.EURO LinBPQ6.0.18
> R:221225/0841Z @:GB7CIP.#32.GBR.EURO #:36638 [Caterham Surrey GBR]
>
> From: G8MNY@GB7CIP.#32.GBR.EURO
> To : TECH@WW
>
> By G8MNY (Corrections Jan 16)
> (8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
>
> Model 99-5076
>
> ___________________________________
> __~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~__ DC Volts 0.25 2.5 10 50 250
> 1000 @ 25k/V __ __ 0.125 1.25 5
> 25 125 500 @ 50k/V ___________________________________
> ____~~~~~~~~~~~~~~~~~~~~~~~~~~~____ DC Amps 50uA 5mA 50mA 500mA
> 10A @ Normal ____ ____ 25uA
> 2,5mA 25mA 240mA 5A @ 2x ____ . ____
> ____ '. ____ AC Volts 3 10 50 250
> 1000 @ 2.5k/V ____ '. . ____ 1.5
> 5 25 125 500 @ 5k/V ____ '. :'\': ____
> ____ '. '_._' ____ 10x dB scales & DC
> isolated AC. ___________________________________
> _____________ _____________ Ohms _FSD 13_ 65_ 650_ 6k5_
> 65k_ _ o- +o _ (|) _ o o _
> _ _ _ _ Accurancy DC 2%, AC 3%
> _ [_ ]rev ___________ _[ _] _
> _______________________________
>
> MULTI METER PRINCIPLES
>
> DC VOLTS 1000 100 10 1 Volts
> To get a meter of just one _10M___1M__100k____11k1____>+
> sensitivity to do many o o o o
> ranges voltage multiplier /_\
> resistors are used. Here +_
> the voltage drop across /~~~\
> the meter is ignored, but _Meter_
> it will affect the lowest 90uA\___/
> 1V scale. _______________________>-
> Series resistors are used
> to protect the switch more Sensitivity is 11k1/V
> from high voltages.
>
> DC CURRENT 100uA 1mA 10mA 100mA
> For current ranges shunts +_______________________>+
> are put across the meter. /~~~\ \_/
> Here the meter resistance _Meter_ o o o o
> is 100_ so it has 10mV drop 100uA\___/ _ _ _
> @ 100uA. The 1mA shunt here 10mV _ 11_ 1_ 0.1_
> is corrected for the 100_ _______________________>-
> meter load.
>
> AC VOLTS
> For AC a rectifier diode is
> used, & normally this alters 1000 100 10 Volts
> the sensitivity, so a different _4M5__450k_____45k____>~
> multiplier arm the DC is used. o o o
> In this circuit only half the /_\
> current goes through the meter +_____<____
> & the 1.1 AC sine wave form /~~~\ D1 ___D2
> factor means that 2.2x meter _Meter_ /_\
> current must flow. Only a 100uA\___/ _100uA
> 100mV is lost in the germanium _______________________>~
> diode D1, so the low voltage
> range can take this into account
> on the scale. D2 can be any type Sensitivity is 4k5/V.
> & protects the low voltage D1.
>
> OHMS
> Here a voltage source is put
> in series with the meter & a
> known resistance that set the
> half scale resistance & includes (actually -ve!)
> the meter load resistance. ___Cal Zero R__________>+
> The higher the battery +_ \_/
> voltage the higher resistance /~~~\ o o o o
> that can be measured, but _Meter_ _10_100_1k_10k_
> becomes a danger for 100uA\___/ _
> sensitive electronics. _ _ _+
> The Cal zero R sets the meter _______________________>-
> sensitive to give full scale _ (actually +ve!)
> ZERO reading on shorting the
> probes depending the battery state.
>
> Note that the battery internal resistance is added to the unknown
> resistance, & this affects the low range scale calibration! Also the
> probe polarity is reversed to that indicated & it is different than
> for digital meters!
>
> ACTUAL MULTIMETER CIRCUIT
> __===========================================================================
> _ I
> __========================= =============== ================
> =========== =_ \/
> __20k__80k__ _ _
> _ /\ /_\ _ _ _Com
> + 10A O/P_ ______________________ _ _
> _ _ o o o _ _ ____ ___ _
> ___________________)_____________)_____)___ _u1_ _ _ _ /15uA\ _
> ICal _ _ 13 _ Low _ 13k __)__)_____)___ _ _
> __ Meter__ ________)_)__ _ 46k _4k7__<__ _ _ _ _
> _ _ _ _ \____/ _12.5k _ _ _ _ _ oNor_ 3k3 _ _
> _ _0.025_ _ _ _ _ _ o o _ _ __> _
> _ _ _ _ _ _ _ ____>_____ _oNor _> X <_ _
> __ o_ _ 5kHi_ _ _ _ _ _ ___<______ <____ o o
> _ __ _4k7__>_____ _ _ 0.475 _ _ ___VCal___
> _oVA/2_Rev Nor _ __ Low _ _ _ _ _
> _____________6k25_ _)_____________))_________________
> _________)_ _ _ __
> __ _ ___________ _
> ___56k25_197k5_1M_5M_18M75___47_650_6k54_____1M87_M5_M1_17k5_
> _4.53_45.3_24k9_ o o o o o o_o o o o_o_o o o
> o o_ o o o o _ I _ _ _
> =========================_=============_
> _================__================ I _
> ===============__________________ +____ 0.25 2.5 10 50 250 1k
> R/5 R 10 100 1k 1k 250 50 10 3 500 50 5 50u
> \________DC_VOLTS_________/ \_____OHMS____/ \___AC_VOLTS___/
> \____DC_mA____/ & dB Scales
>
> The configuration switching between modes & all the ranges is all
> done on just 1 large rotary switch with 3 bridging contacts (I) 5
> wipers of 2 circuits.
>
> Only 4 probe sockets are used, 2 extra for the high current (10A) &
> the DC isolated AC measurement.
>
> Extra switches provide a meter reverse feature & a double sensitivity
> that doubles the number of meter ranges. (has no meaning on ohms!)
>
> This meter's movement is a extremely sensitive @ 15uA for FSD, but
> not very accurate, so it is calibrated with an ICal & VCal presets at
> manufacture.
>
> The AC ranges are calibrated with select on test resistors 2x "4k7
> Low" & the "5k Hi" that accurately allows for the diode forward
> resistance loss & leakage.
>
> Most of the resistors are special values made for the meter, & of
> course they are very accurate & stable 0.5% types.
>
>
> See my tech buls on "Meter Movement Types", "Maplin Mains Meter
> 2000MU-UK", "Edgcume Peebles Megger & Low R", "Edgcume Peebles Earth
> Loop Z", "Car Dwell Angle & RPM Meter", & "Kelvin Varley Voltage
> Divider".
>
>
> Why don't U send an interesting bul?
>
> 73 De John, G8MNY @ GB7CIP
>
>
Related to the diagrams above, it makes me wonder how I could see
the proper graphics ("> (8 Bit ASCII graphics use code page 437 or 850,
Terminal Font") if I read the original bull by using Claws Mail in
Debian Linux.
Btw, thank you John, G8MNY, for your tech bulls!
--
73 de Misko YT7MPB@YU7BPQ.#NSD.SRB.EU
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