Posted by Eric Jacobsen on June 2, 2009, 1:00 am
> rickman wrote:
>>
>> On Jun 1, 10:33 pm, ItsASecretDummy
>> > On Mon, 01 Jun 2009 17:40:20 -0700, John Larkin
>> >
>> >
>> > >Single-electron transistors can sense, well, single electrons.
>> >
>> > >John
>> >
>> > PMTs can be good enough to detect single photon events.
>>
>> Hmmm... I have a $35 digital multimeter that can measure exactly 0
>> volts!
> No, it can't. It can display zero, even with some voltage at the
> input. The issues is the resolution of the meter. Even with the probes
> shorted, you will have some Johnson noise which is generated by the
> resistors in the input circuitry, if the meter is above absolute zero
> degrees. That voltage is too low to be displayed, but it is still there.
> --
> You can't have a sense of humor, if you have no sense!
Yeah, but when it's exactly zero volts, that what the $35 multimeter will
display, so he wasn't incorrect.
;)
Posted by Michael A. Terrell on June 2, 2009, 2:29 pm
Eric Jacobsen wrote:
>
> >
> > rickman wrote:
> >>
> >> On Jun 1, 10:33 pm, ItsASecretDummy
> >> > On Mon, 01 Jun 2009 17:40:20 -0700, John Larkin
> >> >
> >> >
> >> > >Single-electron transistors can sense, well, single electrons.
> >> >
> >> > >John
> >> >
> >> > PMTs can be good enough to detect single photon events.
> >>
> >> Hmmm... I have a $35 digital multimeter that can measure exactly 0
> >> volts!
> >
> >
> > No, it can't. It can display zero, even with some voltage at the
> > input. The issues is the resolution of the meter. Even with the probes
> > shorted, you will have some Johnson noise which is generated by the
> > resistors in the input circuitry, if the meter is above absolute zero
> > degrees. That voltage is too low to be displayed, but it is still there.
> >
> >
> > --
> > You can't have a sense of humor, if you have no sense!
>
> Yeah, but when it's exactly zero volts, that what the $35 multimeter will
> display, so he wasn't incorrect.
>
> ;)
Sigh.
--
You can't have a sense of humor, if you have no sense!
Posted by ItsASecretDummy on June 2, 2009, 9:40 pm
On Mon, 1 Jun 2009 22:00:07 -0700, "Eric Jacobsen"
>>
>> rickman wrote:
>>>
>>> On Jun 1, 10:33 pm, ItsASecretDummy
>>> > On Mon, 01 Jun 2009 17:40:20 -0700, John Larkin
>>> >
>>> >
>>> > >Single-electron transistors can sense, well, single electrons.
>>> >
>>> > >John
>>> >
>>> > PMTs can be good enough to detect single photon events.
>>>
>>> Hmmm... I have a $35 digital multimeter that can measure exactly 0
>>> volts!
>>
>>
>> No, it can't. It can display zero, even with some voltage at the
>> input. The issues is the resolution of the meter. Even with the probes
>> shorted, you will have some Johnson noise which is generated by the
>> resistors in the input circuitry, if the meter is above absolute zero
>> degrees. That voltage is too low to be displayed, but it is still there.
>>
>>
>> --
>> You can't have a sense of humor, if you have no sense!
>Yeah, but when it's exactly zero volts, that what the $35 multimeter will
>display,
] Not if it is turned on it wont.
> so he wasn't incorrect.
Oh yes he was, and so is most of the other responses to him.
If the meter is off, there will be no display. If it is on, it will
not be very likely to read zero volts when probing a bare piece of metal
or shorting the leads.
Like a scale that has been zeroed, one will see drift above and below
the zero line if the scale can resolve to tenths of a gram. It will also
drift as the internal electronics heats up. Not so much with a meter as
with scale electronics, for some reason.
So if the meter has more than 2 digits behind the decimal point, one
will likely see errant values pop in and out.
Posted by John Larkin on June 3, 2009, 5:09 pm
On Tue, 02 Jun 2009 18:40:51 -0700, ItsASecretDummy
>On Mon, 1 Jun 2009 22:00:07 -0700, "Eric Jacobsen"
>>
>>>
>>> rickman wrote:
>>>>
>>>> On Jun 1, 10:33 pm, ItsASecretDummy
>>>> > On Mon, 01 Jun 2009 17:40:20 -0700, John Larkin
>>>> >
>>>> >
>>>> > >Single-electron transistors can sense, well, single electrons.
>>>> >
>>>> > >John
>>>> >
>>>> > PMTs can be good enough to detect single photon events.
>>>>
>>>> Hmmm... I have a $35 digital multimeter that can measure exactly 0
>>>> volts!
>>>
>>>
>>> No, it can't. It can display zero, even with some voltage at the
>>> input. The issues is the resolution of the meter. Even with the probes
>>> shorted, you will have some Johnson noise which is generated by the
>>> resistors in the input circuitry, if the meter is above absolute zero
>>> degrees. That voltage is too low to be displayed, but it is still there.
>>>
>>>
>>> --
>>> You can't have a sense of humor, if you have no sense!
>>
>>Yeah, but when it's exactly zero volts, that what the $35 multimeter will
>>display,
>] Not if it is turned on it wont.
>> so he wasn't incorrect.
> Oh yes he was, and so is most of the other responses to him.
> If the meter is off, there will be no display. If it is on, it will
>not be very likely to read zero volts when probing a bare piece of metal
>or shorting the leads.
> Like a scale that has been zeroed, one will see drift above and below
>the zero line if the scale can resolve to tenths of a gram. It will also
>drift as the internal electronics heats up. Not so much with a meter as
>with scale electronics, for some reason.
> So if the meter has more than 2 digits behind the decimal point, one
>will likely see errant values pop in and out.
Fluke 75, shorted leads, VDC range: steady .000
Fluke 87, ditto: steady 0.000
AlwaysWrong.
John
Posted by rickman on June 4, 2009, 3:03 pm
On Jun 3, 5:09 pm, John Larkin
> On Tue, 02 Jun 2009 18:40:51 -0700, ItsASecretDummy
> >On Mon, 1 Jun 2009 22:00:07 -0700, "Eric Jacobsen"
> >>> rickman wrote:
> >>>> On Jun 1, 10:33 pm, ItsASecretDummy
> >>>> > On Mon, 01 Jun 2009 17:40:20 -0700, John Larkin
> >>>> > >Single-electron transistors can sense, well, single electrons.
> >>>> > >John
> >>>> > PMTs can be good enough to detect single photon events.
> >>>> Hmmm... I have a $35 digital multimeter that can measure exactly 0
> >>>> volts!
> >>> No, it can't. It can display zero, even with some voltage at the
> >>> input. The issues is the resolution of the meter. Even with the probes
> >>> shorted, you will have some Johnson noise which is generated by the
> >>> resistors in the input circuitry, if the meter is above absolute zero
> >>> degrees. That voltage is too low to be displayed, but it is still there.
> >>> --
> >>> You can't have a sense of humor, if you have no sense!
> >>Yeah, but when it's exactly zero volts, that what the $35 multimeter will
> >>display,
> >] Not if it is turned on it wont.
> >> so he wasn't incorrect.
> > Oh yes he was, and so is most of the other responses to him.
> > If the meter is off, there will be no display. If it is on, it will
> >not be very likely to read zero volts when probing a bare piece of metal
> >or shorting the leads.
> > Like a scale that has been zeroed, one will see drift above and below
> >the zero line if the scale can resolve to tenths of a gram. It will also
> >drift as the internal electronics heats up. Not so much with a meter as
> >with scale electronics, for some reason.
> > So if the meter has more than 2 digits behind the decimal point, one
> >will likely see errant values pop in and out.
> Fluke 75, shorted leads, VDC range: steady .000
> Fluke 87, ditto: steady 0.000
> AlwaysWrong.
> John
Are you going to return these meters for repair?
Rick
>>
>> On Jun 1, 10:33 pm, ItsASecretDummy
>> > On Mon, 01 Jun 2009 17:40:20 -0700, John Larkin
>> >
>> >
>> > >Single-electron transistors can sense, well, single electrons.
>> >
>> > >John
>> >
>> > PMTs can be good enough to detect single photon events.
>>
>> Hmmm... I have a $35 digital multimeter that can measure exactly 0
>> volts!
> No, it can't. It can display zero, even with some voltage at the
> input. The issues is the resolution of the meter. Even with the probes
> shorted, you will have some Johnson noise which is generated by the
> resistors in the input circuitry, if the meter is above absolute zero
> degrees. That voltage is too low to be displayed, but it is still there.
> --
> You can't have a sense of humor, if you have no sense!