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Just for fun i am searching for a ANALOGUE oscilloscope (already have rigol digital)
I would prefer a cheap new than a second hand but may end in second hand.
i have found J2459 wincom in alibaba, which costs 55usd ?! at 2mhz, and ideal for "fun" but i cand found how and at what cost send in...
thanx everyone,
original query was why lm339 does not detect positive rail which answer my mistake (tahnx)
best solution imho is voltage divider which should work perfect for this
However because final project will eun with 14-16 volt input i see no rail-to-rail with than input (all rr are up to 5v) so voltage division is only option ..
Hi
i am testing a LM339, i see that it described to detect up to power supply with a few mV offset
however iwth a 5 Volt input i see that detection is triggered when i drop negative input to around 3,9 volt (and positive to 5)
while detection from 0 is nearly instand 10-50mV and triggered
do...
is there any instrument, who can measure temperature of IC itself
"normal" cheap IR thermometer need a very big surface to scan for correct temperature
Hi
while searching for some telphone circuits i come across this article -> https://en.wikipedia.org/wiki/Line_isolation_transformer
it claims that "wet" type transformer can pass DC, therefore you can detect on/off hook ?
since i never come across this, is this true ? if yes does anyone knows...
Hello
i am searching ,without , lack the protocol of UTC (or CoC).
that looking for the description OR a IC that decodes it !
* UTC is a protocol for controling PTZ cameras via coaxial cable (without extra data cables)
HI first thank's all for your time
to sum , the circuit is going to be powered from external PSU (12volt) that psu maybe or maybe not have 0v=gnd and i do not know it !
1) i do will use bridge on final project for sure .. now test !
2) 0V ? for example 0v of 7805 ? that rail maybe connected...
the only wrong is that it did NOT work,
Here is a quick schematic
as long as point G connected to negative of 7805. Value measurement with handheld DVM, between points G<->B, changes.
Furthermore different values exist if i connect my circuit to telephone company A FXS than telephone company...
i can not be sure where it will be power from
maybe would need a external psu maybe connected direct to ground !
therefore if i understand correct "direct measurement" is not correct to my case ?
is there any idea for isolation voltage from telephone line ? i see most systems use opto's
is...
yes i did, yes handheld DVM do not affect it
however afaik ADC measure's voltages from its ground to a value
but as i said "my measuring device" will/must be powered from a power source (12volt)
and as long as i connect ANY wall powered PSU , measurements change
even handheld DVM measures...
in US AND Europe its tip=0 ring =-48 on-hook and -20, -28 off-hook
that bring me back to 0 since , original question "how to measure telephone line without affecting it" grrr
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