Your body is a capacitor, charged to varying voltage as you move around.? Any sensitive meter will jump around as you approach or withdraw.
?
Dave Wise
?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]]
On Behalf Of Askild via groups.io
Sent: Sunday, November 07, 2021 10:34 PM
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 401 c VTVM
?
Hi Mark,
Its normal for voltmeters with very high input impedance to not show stable 0V when probe is hanging free. Mine also jump around when touching the probe.?
The input impedance of the 410C is about 100MOhm, compared to most multimeters today that have 10MOhm.
To see if the voltmeter is showing 0V with no voltage applied, you need to short the voltmeter probe and the ground wire.
?
Hello one and all,
I have recently acquired a HP 410 C meter from a friend.
It works great measuring resistance. I do not have the AC probe that may have come with it, so I cannot attest to its AC measuring accuracy. However when I try to measure something as simple as a AAA or 9-volt battery the meter does something I am unable to
explain.
The meter movement will not land or stay on zero when I turn the function switch to DC+ or DC-. I find that when I handle the DC probe it is when the meter goes crazy. (also technical term used in describing human behavior).
If I run my hand along the probe wire I get the same reaction.?
If I conduct the test with out letting the meter settle at zero I get a very accurate reading.
I have checked the internals of the probe and find that the center core of the coax is connected to the resistor which is connected to the tip.
The shield is cut back and covered with shrink tubing eliminating any possible "short"
I have checked the continuity of both the shield and the inner wire of the coax and there is nothing unusual to report.
Any suggestions would be greatly appreciated
Respectfully
Mark
|
On November 8, 2021 10:27:59 AM "Chris Wilkson via groups.io" <cwilkson@...> wrote: Real quick note.
I've gotten many inquiries on the Model M keyboards.
They are keepers...I use both of them every day. Yeah I think many people inexplicably interpreted your initial post as "I want to get rid of all of this stuff". It was actually pretty clear that this was not your intention. -Dave -- Dave McGuire, AK4HZ New Kensington, PA
|
Real quick note.
I've gotten many inquiries on the Model M keyboards.
They are keepers...I use both of them every day.
|
Re: Placing Shelf on Casters for HP Equipment
On 11/8/21 6:45 AM, Paul Bicknell wrote: Equipment can have rack wings this allows the equipment to be bolted to the front of the 19 rack to prevent it moving ( NOT to Support it or hold it up )
*The equipment must be supported from front to back on shelves? or side runners* Supporting from those wings (commonly called "ears") is referred to as "cantilevered mounting". This is actually very common, acceptable, and the designers' intentions for many things. You'd not mount, say, an HP 8566 that way, but many HP instruments are just fine with cantilevered mounting. Use judgement. These will have square holes down both sides and this is where the cage nuts go as mentioned in an earlier mail Note that not all holes are square; I found it to be about 50/50. There are square holes, round holes, and threaded round holes, all of which are common. -Dave -- Dave McGuire, AK4HZ New Kensington, PA
|
Re: Placing Shelf on Casters for HP Equipment
Yes, I forgot to mention in my earlier post that I acquired all three of my racks for free. With some patience and a lot of trolling, one can usually find a suitable rack. I know that they are around here in Central Florida, and I was able to find them along Colorado¡¯s front range as well.
DaveD
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Show quoted text
On Nov 8, 2021, at 09:20, Paul Amaranth <paul@...> wrote:
?I like the four post racks, the two post relay racks never
seemed a good choice for test equipment.
With some scrounging, they can be very cheap. I got one free
off of craigslist and the last one I got was something like
$10 at an auction. I also have a couple of half size rack
cabinets that had equipment built into them that are pretty
handy.
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@... | Unix/Linux - We don't do windows
|
Re: Placing Shelf on Casters for HP Equipment
I like the four post racks, the two post relay racks never
seemed a good choice for test equipment.
With some scrounging, they can be very cheap. I got one free
off of craigslist and the last one I got was something like
$10 at an auction. I also have a couple of half size rack
cabinets that had equipment built into them that are pretty
handy.
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@... | Unix/Linux - We don't do windows
|
Re: Placing Shelf on Casters for HP Equipment
I've used the Starcase racks and had good luck with them.? The ability to access through (and mount things to) all four sides is nice.
But as Dave said, the base configuration is very wobbly.? Starcase has various corner, diagonal, and side braces that are almost mandatory to stiffen the frame.? But with those installed, I really, really like these racks.
John
On Nov 8, 2021, at 7:28 AM, Dave Daniel < kc0wjn@...> wrote:
toggle quoted message
Show quoted text
A lot of excellent points have been made in this thread so far. Here are some additional considerations:
The ¡°Metro¡± wire shelving works reasonably well. Using casters works if one doesn¡¯t overload the shelves. Even if one overloadsthe shelves a bit they will work unless one tries to roll the loaded shelving. A perticularly nasty failure mode for these is for the caster and the cylinder into which it is screwed to break out of the leg tubing sideways (ask me how I know).
Uline also sells metal wire shelving. While a bit more expensive, those shelf units are better built.
Based on ths OP¡¯s question about the StarTech rack, I have found StarTech¡¯s products to not be very reliable. Furthermore, that open frame has very little rigidity. Installing light-weight items in it will stiffen it, particularly if the items are fastened to the rack at both the front and rear of the rack. Installing heavy items will *require* being fastened at front and back. Racks with side covers fastened to the rack frame will be much stronger.
I keep my heavy instruments (HP 8566B and HP 8660D) on the bench and lighter items (HP 339A and others) in my rack on rack shelves and move them off the shelves and onto the bench when I want to use them. I have yet to find a convenient arrangement of rack, bench and the position of instruments in the rack that affords useful access to all instruments in the rack. The closest I ever came to that was to have a short rack sitting on the bench. But eventually I just stacked the instruments on top of one another without the rack. My rack now sits in the lab away from the. ench and is used onlg to store instruments.
I have had three heavy-duty racks over the last forty or so years, all of which were intended for heavy items. The first was a rack intended to hold Dictphone logging recorders and was built like a tank. The second and third were originally used to hold servers. The one I currently have (probably sinething like 32U tall) is very strong, but I wouldn¡¯t attemp to roll it without unloading a few pieces from it first.
Be very careful about weight distribution (top to bottom) when loading a rack or shelving, particularly if one intends to try and roll it around. Heavy items down low, lighter items towards the top.
DaveD
On Nov 8, 2021, at 06:45, Paul Bicknell <admin@...> wrote:
?
Hi all
?
Just a few observations and hopefully a bit of help
?
Regarding? 19 inch racks? don¡¯t be too hard on the new be as like a lot of? people getting into the electronics industry
Have an excellent Brain on them but often lacking in practical skills
That is why I spent over a month at the beginning of the year designing and making a new lab for mature student training
This will hopefully continue with passing on hands on experience with test equipment ( prior to lock down we had over 200 students pass through )
?
Back to racks, ?a typical 19 inch rack made by HP can be seen in the Photos file on this site and in 0 to 99 Equipment Lab Photos
?
/g/HP-Agilent-Keysight-equipment/photo/256676/3227464?p=Created%2C%2C%2C20%2C2%2C0%2C0
?
Now back to the original question from Matt
as do we know if Matt is using modem or older test equipment that is 19 inch compatible and how much does he have
?
Your best configuration might be to split it up as in use a 19 rack for the heavy stuff and a deep bench with a shelf for lighter equipment etc.
?
all can be on wheels , regarding centre of gravity my standard is all the wheels should be mounted so the vertical line always falls 2 inches outside the rack
?
OK Matt a few bits of info on 19 racks?
Equipment can have rack wings this allows the equipment to be bolted to the front of the 19 rack to prevent it moving ( NOT to Support it or hold it up )
The equipment must be supported from front to back on shelves? or side runners
?
This also allows for equipment to be pulled out so you can reconfigure connections on the back
?
So for a 19 rack to be useful to hold and use test equipment it requires 4 vertical supports 2 at the front and 2 at the rear
These will have square holes down both sides and this is where the cage nuts go as mentioned in an earlier mail
?
Now you require the equipment supports from back to front the best racks and easiest to configure?
have additional cage nut holes on side face of all 4 verticals corners of the rack
?
Other arrangements for the support rails are available but less friendly when making up out of second hand components
?
Please feel free to come back as selecting and installing cage nuts is a neck that must be learnt and can be one of the essayist ways to draw blood
?
Regards Paul
?
?
?
?
From: [email protected] [mailto:[email protected]] On Behalf Of Michael A. Terrell
Sent: 08 November 2021 08:34
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] Placing Shelf on Casters for HP Equipment
?
There are also 23" wide racks that came from the Telco industry.
I have two, dual sized enclosed racks They are 19", but you can remove the doors and side panels, then turn it 90 degrees to use it as a 23" rack.
They are from some long gone National Semiconductor Datachecker POS systems that were scrapped 25 years ago.
?
On Sun, Nov 7, 2021 at 10:31 PM Dave McGuire <mcguire@...> wrote:
On 11/7/21 8:38 PM, Matt Huszagh wrote:
> I googled "HP test equipment rack" and the 19" rack popped up. I have
> seen these before, though I didn't know the term (or know that it was a
> standard). I also did not know that these are what HP, Agilent and
> Keysight use for their test equipment racks.
? ?Well, they followed the 19" rack standard.? Just like all of the
computer manufacturers (HP included) followed it too.
? ?The vernacular: One "rack U" (rack unit) is 1.75".? A "1U"
rack-mounted device is 1.75" tall, a "2U" chassis is 3.5", etc.? About
95% of the hardware you'll run across, test equipment and server-class
computers alike, is sized in these increments.? Soon you'll be able to
recognize them on sight and plan out your rack space allocations: "Oh, I
see that HP 3325A is a 3U box".? "Ah, I can put a 1U file server right
here".
? ?Look for a picture of the front one of these racks, empty, and look
at the holes facing you on the left and right.? Notice the spacing
pattern of the holes.? It looks irregular, but if you stare at it for a
moment you'll see that they're spaced out for 1.75" increments.
? ?All of this works amazingly well, and you will love it.
? ?This isn't just test equipment stuff.? If you haven't ever seen a
datacenter in person, surely you've seen pictures of them.? Those are
the same racks.
? ?Keyboardless synthesizers, signal processors, and amplifiers in
recording studios and on on concert stages...same racks.
? ?AT&T came up with this standard for telephony equipment in
1922...Yes, 99 years ago.
> I'm not sure if this is a good excuse but I'm relatively young (< 30)
> and only been doing electronics for the last couple years, when I
> started teaching myself. I also don't come from an engineering
> background, so I've probably missed some things that are evident to
> others in the field. I did study physics undergrad though, and research
> is one of the places I've come across these. But, none of us were too
> concerned that these were called 19" racks.
? ?It's not a good excuse. ;)? But it's never too late to catch up, and
you can fill in all of the knowledge blanks here.
? ? ? ? ? ? -Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
|
Re: Placing Shelf on Casters for HP Equipment
A lot of excellent points have been made in this thread so far. Here are some additional considerations:
The ¡°Metro¡± wire shelving works reasonably well. Using casters works if one doesn¡¯t overload the shelves. Even if one overloadsthe shelves a bit they will work unless one tries to roll the loaded shelving. A perticularly nasty failure mode for these is for the caster and the cylinder into which it is screwed to break out of the leg tubing sideways (ask me how I know).
Uline also sells metal wire shelving. While a bit more expensive, those shelf units are better built.
Based on ths OP¡¯s question about the StarTech rack, I have found StarTech¡¯s products to not be very reliable. Furthermore, that open frame has very little rigidity. Installing light-weight items in it will stiffen it, particularly if the items are fastened to the rack at both the front and rear of the rack. Installing heavy items will *require* being fastened at front and back. Racks with side covers fastened to the rack frame will be much stronger.
I keep my heavy instruments (HP 8566B and HP 8660D) on the bench and lighter items (HP 339A and others) in my rack on rack shelves and move them off the shelves and onto the bench when I want to use them. I have yet to find a convenient arrangement of rack, bench and the position of instruments in the rack that affords useful access to all instruments in the rack. The closest I ever came to that was to have a short rack sitting on the bench. But eventually I just stacked the instruments on top of one another without the rack. My rack now sits in the lab away from the. ench and is used onlg to store instruments.
I have had three heavy-duty racks over the last forty or so years, all of which were intended for heavy items. The first was a rack intended to hold Dictphone logging recorders and was built like a tank. The second and third were originally used to hold servers. The one I currently have (probably sinething like 32U tall) is very strong, but I wouldn¡¯t attemp to roll it without unloading a few pieces from it first.
Be very careful about weight distribution (top to bottom) when loading a rack or shelving, particularly if one intends to try and roll it around. Heavy items down low, lighter items towards the top.
DaveD
toggle quoted message
Show quoted text
On Nov 8, 2021, at 06:45, Paul Bicknell <admin@...> wrote:
? Hi all ? Just a few observations and hopefully a bit of help ? Regarding? 19 inch racks? don¡¯t be too hard on the new be as like a lot of? people getting into the electronics industry Have an excellent Brain on them but often lacking in practical skills That is why I spent over a month at the beginning of the year designing and making a new lab for mature student training This will hopefully continue with passing on hands on experience with test equipment ( prior to lock down we had over 200 students pass through ) ? Back to racks, ?a typical 19 inch rack made by HP can be seen in the Photos file on this site and in 0 to 99 Equipment Lab Photos ? /g/HP-Agilent-Keysight-equipment/photo/256676/3227464?p=Created%2C%2C%2C20%2C2%2C0%2C0 ? Now back to the original question from Matt as do we know if Matt is using modem or older test equipment that is 19 inch compatible and how much does he have ? Your best configuration might be to split it up as in use a 19 rack for the heavy stuff and a deep bench with a shelf for lighter equipment etc. ? all can be on wheels , regarding centre of gravity my standard is all the wheels should be mounted so the vertical line always falls 2 inches outside the rack ? OK Matt a few bits of info on 19 racks? Equipment can have rack wings this allows the equipment to be bolted to the front of the 19 rack to prevent it moving ( NOT to Support it or hold it up ) The equipment must be supported from front to back on shelves? or side runners ? This also allows for equipment to be pulled out so you can reconfigure connections on the back ? So for a 19 rack to be useful to hold and use test equipment it requires 4 vertical supports 2 at the front and 2 at the rear These will have square holes down both sides and this is where the cage nuts go as mentioned in an earlier mail ? Now you require the equipment supports from back to front the best racks and easiest to configure? have additional cage nut holes on side face of all 4 verticals corners of the rack ? Other arrangements for the support rails are available but less friendly when making up out of second hand components ? Please feel free to come back as selecting and installing cage nuts is a neck that must be learnt and can be one of the essayist ways to draw blood ? Regards Paul ? ? ? ? From: [email protected] [mailto:[email protected]] On Behalf Of Michael A. Terrell
Sent: 08 November 2021 08:34
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] Placing Shelf on Casters for HP Equipment ? There are also 23" wide racks that came from the Telco industry. I have two, dual sized enclosed racks They are 19", but you can remove the doors and side panels, then turn it 90 degrees to use it as a 23" rack. They are from some long gone National Semiconductor Datachecker POS systems that were scrapped 25 years ago. ? On Sun, Nov 7, 2021 at 10:31 PM Dave McGuire <mcguire@...> wrote: On 11/7/21 8:38 PM, Matt Huszagh wrote:
> I googled "HP test equipment rack" and the 19" rack popped up. I have
> seen these before, though I didn't know the term (or know that it was a
> standard). I also did not know that these are what HP, Agilent and
> Keysight use for their test equipment racks.
? ?Well, they followed the 19" rack standard.? Just like all of the
computer manufacturers (HP included) followed it too.
? ?The vernacular: One "rack U" (rack unit) is 1.75".? A "1U"
rack-mounted device is 1.75" tall, a "2U" chassis is 3.5", etc.? About
95% of the hardware you'll run across, test equipment and server-class
computers alike, is sized in these increments.? Soon you'll be able to
recognize them on sight and plan out your rack space allocations: "Oh, I
see that HP 3325A is a 3U box".? "Ah, I can put a 1U file server right
here".
? ?Look for a picture of the front one of these racks, empty, and look
at the holes facing you on the left and right.? Notice the spacing
pattern of the holes.? It looks irregular, but if you stare at it for a
moment you'll see that they're spaced out for 1.75" increments.
? ?All of this works amazingly well, and you will love it.
? ?This isn't just test equipment stuff.? If you haven't ever seen a
datacenter in person, surely you've seen pictures of them.? Those are
the same racks.
? ?Keyboardless synthesizers, signal processors, and amplifiers in
recording studios and on on concert stages...same racks.
? ?AT&T came up with this standard for telephony equipment in
1922...Yes, 99 years ago.
> I'm not sure if this is a good excuse but I'm relatively young (< 30)
> and only been doing electronics for the last couple years, when I
> started teaching myself. I also don't come from an engineering
> background, so I've probably missed some things that are evident to
> others in the field. I did study physics undergrad though, and research
> is one of the places I've come across these. But, none of us were too
> concerned that these were called 19" racks.
? ?It's not a good excuse. ;)? But it's never too late to catch up, and
you can fill in all of the knowledge blanks here.
? ? ? ? ? ? -Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
|
Thanks Jim. I have made plenty of typos don¡¯t worry, I said 132V below but meant -132V.
I replaced C12 to no effect, it measure fine can you believe it.
The last thing I decided to check tonight was the AC voltage from my variac transformer because I am seeing low voltages all through the circuit. Guess what, my variac is way off at 115Vac, it measures about 85Vac. I have never had to check it as it is spot on at 240Vac which is fine for Australia. I am starting to look like a real amateur, not something I even considered checking. Anyway, the voltage at R30/31/40 is now -172Vac. I will check the other voltages as per recommendations below. The device is working really well, lovely clean sine wave across the spectrum. It¡¯s just R30 that has me worried. Perhaps I will replace it to see if that helps.?
Cheers
Richard
|
Re: Placing Shelf on Casters for HP Equipment
Hi all ? Just a few observations and hopefully a bit of help ? Regarding? 19 inch racks? don¡¯t be too hard on the new be as like a lot of? people getting into the electronics industry Have an excellent Brain on them but often lacking in practical skills That is why I spent over a month at the beginning of the year designing and making a new lab for mature student training This will hopefully continue with passing on hands on experience with test equipment ( prior to lock down we had over 200 students pass through ) ? Back to racks, ?a typical 19 inch rack made by HP can be seen in the Photos file on this site and in 0 to 99 Equipment Lab Photos ? /g/HP-Agilent-Keysight-equipment/photo/256676/3227464?p=Created%2C%2C%2C20%2C2%2C0%2C0 ? Now back to the original question from Matt as do we know if Matt is using modem or older test equipment that is 19 inch compatible and how much does he have ? Your best configuration might be to split it up as in use a 19 rack for the heavy stuff and a deep bench with a shelf for lighter equipment etc. ? all can be on wheels , regarding centre of gravity my standard is all the wheels should be mounted so the vertical line always falls 2 inches outside the rack ? OK Matt a few bits of info on 19 racks? Equipment can have rack wings this allows the equipment to be bolted to the front of the 19 rack to prevent it moving ( NOT to Support it or hold it up ) The equipment must be supported from front to back on shelves? or side runners ? This also allows for equipment to be pulled out so you can reconfigure connections on the back ? So for a 19 rack to be useful to hold and use test equipment it requires 4 vertical supports 2 at the front and 2 at the rear These will have square holes down both sides and this is where the cage nuts go as mentioned in an earlier mail ? Now you require the equipment supports from back to front the best racks and easiest to configure? have additional cage nut holes on side face of all 4 verticals corners of the rack ? Other arrangements for the support rails are available but less friendly when making up out of second hand components ? Please feel free to come back as selecting and installing cage nuts is a neck that must be learnt and can be one of the essayist ways to draw blood ? Regards Paul ? ? ? ?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Michael A. Terrell
Sent: 08 November 2021 08:34
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] Placing Shelf on Casters for HP Equipment ? There are also 23" wide racks that came from the Telco industry. I have two, dual sized enclosed racks They are 19", but you can remove the doors and side panels, then turn it 90 degrees to use it as a 23" rack. They are from some long gone National Semiconductor Datachecker POS systems that were scrapped 25 years ago. ? On Sun, Nov 7, 2021 at 10:31 PM Dave McGuire <mcguire@...> wrote: On 11/7/21 8:38 PM, Matt Huszagh wrote:
> I googled "HP test equipment rack" and the 19" rack popped up. I have
> seen these before, though I didn't know the term (or know that it was a
> standard). I also did not know that these are what HP, Agilent and
> Keysight use for their test equipment racks.
? ?Well, they followed the 19" rack standard.? Just like all of the
computer manufacturers (HP included) followed it too.
? ?The vernacular: One "rack U" (rack unit) is 1.75".? A "1U"
rack-mounted device is 1.75" tall, a "2U" chassis is 3.5", etc.? About
95% of the hardware you'll run across, test equipment and server-class
computers alike, is sized in these increments.? Soon you'll be able to
recognize them on sight and plan out your rack space allocations: "Oh, I
see that HP 3325A is a 3U box".? "Ah, I can put a 1U file server right
here".
? ?Look for a picture of the front one of these racks, empty, and look
at the holes facing you on the left and right.? Notice the spacing
pattern of the holes.? It looks irregular, but if you stare at it for a
moment you'll see that they're spaced out for 1.75" increments.
? ?All of this works amazingly well, and you will love it.
? ?This isn't just test equipment stuff.? If you haven't ever seen a
datacenter in person, surely you've seen pictures of them.? Those are
the same racks.
? ?Keyboardless synthesizers, signal processors, and amplifiers in
recording studios and on on concert stages...same racks.
? ?AT&T came up with this standard for telephony equipment in
1922...Yes, 99 years ago.
> I'm not sure if this is a good excuse but I'm relatively young (< 30)
> and only been doing electronics for the last couple years, when I
> started teaching myself. I also don't come from an engineering
> background, so I've probably missed some things that are evident to
> others in the field. I did study physics undergrad though, and research
> is one of the places I've come across these. But, none of us were too
> concerned that these were called 19" racks.
? ?It's not a good excuse. ;)? But it's never too late to catch up, and
you can fill in all of the knowledge blanks here.
? ? ? ? ? ? -Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
|
Re: OT: Standalone programmer for PIC17C44 (PLCC44)
Oops - typo LIVES the other side of the planet
toggle quoted message
Show quoted text
-----Original Message----- From: [email protected]< [email protected]> On Behalf Of David C. Partridge Sent: 08 November 2021 10:14 To: [email protected]Subject: [HP-Agilent-Keysight-equipment] OT: Standalone programmer for PIC17C44 (PLCC44) Yes I know it's OTP, and the device is old ... but I do have programmers that will handle the PIC17C44 (Dataman 48XP, and Conitec Galep-4). A friend of mine who loves the other side of the planet asked if I could recommend a cheap programmer to programme these devices. I got my Dataman 48XP really cheap at a radio rally - an amazing bargain I thought - normally not so. Any suggestions most welcome. Thanks David
|
OT: Standalone programmer for PIC17C44 (PLCC44)
Yes I know it's OTP, and the device is old ... but I do have programmers
that will handle the PIC17C44 (Dataman 48XP, and Conitec Galep-4).
A friend of mine who loves the other side of the planet asked if I could
recommend a cheap programmer to programme these devices.
I got my Dataman 48XP really cheap at a radio rally - an amazing bargain I
thought - normally not so.
Any suggestions most welcome.
Thanks
David
|
Re: Placing Shelf on Casters for HP Equipment
There are also 23" wide racks that came from the Telco industry.
I have two, dual sized enclosed racks They are 19", but you can remove the doors and side panels, then turn it 90 degrees to use it as a 23" rack.
They are from some long gone National Semiconductor Datachecker POS systems that were scrapped 25 years ago.
On Sun, Nov 7, 2021 at 10:31 PM Dave McGuire < mcguire@...> wrote: On 11/7/21 8:38 PM, Matt Huszagh wrote:
> I googled "HP test equipment rack" and the 19" rack popped up. I have
> seen these before, though I didn't know the term (or know that it was a
> standard). I also did not know that these are what HP, Agilent and
> Keysight use for their test equipment racks.
? ?Well, they followed the 19" rack standard.? Just like all of the
computer manufacturers (HP included) followed it too.
? ?The vernacular: One "rack U" (rack unit) is 1.75".? A "1U"
rack-mounted device is 1.75" tall, a "2U" chassis is 3.5", etc.? About
95% of the hardware you'll run across, test equipment and server-class
computers alike, is sized in these increments.? Soon you'll be able to
recognize them on sight and plan out your rack space allocations: "Oh, I
see that HP 3325A is a 3U box".? "Ah, I can put a 1U file server right
here".
? ?Look for a picture of the front one of these racks, empty, and look
at the holes facing you on the left and right.? Notice the spacing
pattern of the holes.? It looks irregular, but if you stare at it for a
moment you'll see that they're spaced out for 1.75" increments.
? ?All of this works amazingly well, and you will love it.
? ?This isn't just test equipment stuff.? If you haven't ever seen a
datacenter in person, surely you've seen pictures of them.? Those are
the same racks.
? ?Keyboardless synthesizers, signal processors, and amplifiers in
recording studios and on on concert stages...same racks.
? ?AT&T came up with this standard for telephony equipment in
1922...Yes, 99 years ago.
> I'm not sure if this is a good excuse but I'm relatively young (< 30)
> and only been doing electronics for the last couple years, when I
> started teaching myself. I also don't come from an engineering
> background, so I've probably missed some things that are evident to
> others in the field. I did study physics undergrad though, and research
> is one of the places I've come across these. But, none of us were too
> concerned that these were called 19" racks.
? ?It's not a good excuse. ;)? But it's never too late to catch up, and
you can fill in all of the knowledge blanks here.
? ? ? ? ? ? -Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
|
Re: Placing Shelf on Casters for HP Equipment
These 19" racks seem great. Thanks for pointing them out! I'm now
considering rack-mounting my equipment and delegating the shelf for
other purposes. Anyone have experience with StarTech? For example, this
looks good
There are also NavePoint options (which Dave mentioned), but are a tad
more expensive and have a lower rated weight capacity.
Matt
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Hi Mark,
Its normal for voltmeters with very high input impedance to not show stable 0V when probe is hanging free. Mine also jump around when touching the probe.? The input impedance of the 410C is about 100MOhm, compared to most multimeters today that have 10MOhm.
To see if the voltmeter is showing 0V with no voltage applied, you need to short the voltmeter probe and the ground wire.
Regards, Askild ?
Hello one and all,
I have recently acquired a HP 410 C meter from a friend.
It works great measuring resistance. I do not have the AC probe that may have come with it, so I cannot attest to its AC measuring accuracy. However when I try to measure something as simple as a AAA or 9-volt battery the meter does something I am unable to explain.
The meter movement will not land or stay on zero when I turn the function switch to DC+ or DC-. I find that when I handle the DC probe it is when the meter goes crazy. (also technical term used in describing human behavior).
If I run my hand along the probe wire I get the same reaction.?
If I conduct the test with out letting the meter settle at zero I get a very accurate reading.
I have checked the internals of the probe and find that the center core of the coax is connected to the resistor which is connected to the tip.
The shield is cut back and covered with shrink tubing eliminating any possible "short"
I have checked the continuity of both the shield and the inner wire of the coax and there is nothing unusual to report.
Any suggestions would be greatly appreciated
Respectfully
Mark
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Re: Placing Shelf on Casters for HP Equipment
Bruce:
Strangely, one just gets used to reading everything. No neck turn needed....
I have to do that a lot when working on a box that needs access to both top and bottom during troubleshooting...
? ? Which seems to be a lot....So, try it, you might get used to it....
Dan in Chandler, AZ
PS: the outlet strips shown in the photos are all plugged into the Elgar 3006 in the corner. It is rated for 27 amps @120VAC and runs from a separate 240VAC line.?
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Re: Placing Shelf on Casters for HP Equipment
Very cleverly done Dan. I like it. ¨C Mike ? Mike B. Feher, N4FS 89 Arnold Blvd. Howell NJ 07731 848-245-9115 ?
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From: [email protected] < [email protected]> On Behalf Of Daniel Nelson via groups.io Sent: Sunday, November 7, 2021 11:15 PM To: [email protected]Subject: Re: [HP-Agilent-Keysight-equipment] Placing Shelf on Casters for HP Equipment ? After some years of fooling around with stacking stuff, I gave that up and moved everything on edge. The bench is made of pine 2x4 with 1-1/8" Black Iron pipe for shelf support and library board for the decking.? There are outlet strips on the wall behind and a power conditioner on the bottom in the corner. See the photos. I often work on things with the displays turned, so no problem putting things in on edge. At least I can take one item out at a time. Some connections have been extended to the front using the top rack flange as a holder for BNC bulkhead connectors.? So, this has worked for me and provides a really good packing density. Photos attached.
Dan in Chandler, AZ
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Re: Placing Shelf on Casters for HP Equipment
? I like the casters you chose.? The leveling feet will allow you to unload the casters which will stabilize the cart and prevent flat-spotting the wheels over time.? It might save it from making dents in the hardwood as well.? It looks like a good design as long as the c-channels are well attached. When loading it I would recommend trying to keep the COG low if practical just as an added precaution.? When you roll it keep the speed low and you should be okay even if the seemingly inevitable cable flop under a wheel happens as it always seems to.? I also like the shelves, but the ribs may be hard on the feet if you slide an instrument sideway.? Many Metro racks have wire shelves which aren't compatible with the feet on instruments.? Even with the plastic or wood shelf covers the feet tend to catch and can break.? Obviously you won't want to put any equipment on slides on a rack like this.
? Metro racks are great but I have seen several plastic corner clips fail over the years.? That can cause items to slide off a shelf but usually they don't drop far enough to do that.? I think the failures were due to the interlocking ring shearing off in the post due to shock loads from rolling over joints in concrete and such.? I have some aluminum corner clips that I use if I am loading a rack up heavy.? I have never had seen of those fail, but I don't know where to get them.? All my Metro racks came second hand after heavy abuse and the spare clips were salvaged off damaged ones.? Now I have so much stuff on and around them I can't roll them.
Good luck with your shelf,
Clay Scott
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Re: Placing Shelf on Casters for HP Equipment
While we¡¯re on the subject I¡¯ll share a few other things I think I know about instrumentation racks.
I agree the best name for them is a ¡°19 inch rack¡±. That¡¯s the actual width of the front panel of an instrument that will fit it. Note: many instruments are made to fit in this size rack but may not have flange kits or what I¡¯ve heard called ¡°ears¡± that have to be the same height as the instrument (U size mentioned by another contributor here) and mounted on the sides of the instrument with screws then mounted in the rack.
Most modern racks do not have threaded holes for the flanges to be mounted to. Instead a special nut with an integrated clip is needed for each flange hole. They are clipped onto the rack at each point on both sides where there is a flange hole. This is one way in which the variety of instrument heights is accommodated.
To support the weight of equipment, the rack usually has L shaped rails that mount to the sides at front and back to support the weight of each instrument. In really fancy setups especially where in rack serviceability is needed, slides are used instead of simple rails.
These racks often have solid sheet metal sides and some even have doors to cover front and or the back often with locks to prevent tampering with the equipment or interconnections. With covers they are often called instrument cabinets. Now that they have solid sides, they often need and come with fans near the bottom and perforated top or sides to manage heat created by the instruments. They usually have power distribution built in too.
Another type of rack, usually called a ¡°telco rack¡± are completely open and the vertical sides are often made of ~3¡± wide aluminum U channel. These usually have threaded holes every 1/2¡± on each side the entire length. These racks are often 7 or 8 feet tall. These aren¡¯t very useful for instruments and usually hold shallow network gear or patch panels.
Mark
Ex HP/Agilent Employee
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On Nov 7, 2021, at 5:38 PM, Matt Huszagh <huszaghmatt@...> wrote:
?"Dave McGuire" <mcguire@...> writes:
You're not familiar with 19" racks, which have been ubiquitous in
many industries for about a century?
- test equipment
- computing
- telephony
- sound reinforcement
- pro music gear (synthesizers, audio processing)
- industrial automation
- [probably more that I can't think of offhand]
I'm not trying to talk down to you, man, but I can't see how anyone
who has lived on Earth for awhile couldn't know about these. Heck, my
grandmother suggested to me that I should get one when I was about 14,
in the 80s. I googled "HP test equipment rack" and the 19" rack popped up. I have
seen these before, though I didn't know the term (or know that it was a
standard). I also did not know that these are what HP, Agilent and
Keysight use for their test equipment racks.
I'm not sure if this is a good excuse but I'm relatively young (< 30)
and only been doing electronics for the last couple years, when I
started teaching myself. I also don't come from an engineering
background, so I've probably missed some things that are evident to
others in the field. I did study physics undergrad though, and research
is one of the places I've come across these. But, none of us were too
concerned that these were called 19" racks.
Matt
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Re: Placing Shelf on Casters for HP Equipment
Dan -
Really dense - how is your neck :-)
Cheers!
Bruce
Quoting "Daniel Nelson via groups.io" <djn@...>:
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After some years of fooling around with stacking stuff, I gave that up and moved everything on edge. The bench is made of pine 2x4 with 1-1/8" Black Iron pipe for shelf support and library board for the decking.? There are outlet strips on the wall behind and a power conditioner on the bottom in the corner. See the photos. I often work on things with the displays turned, so no problem putting things in on edge. At least I can take one item out at a time. Some connections have been extended to the front using the top rack flange as a holder for BNC bulkhead connectors.? So, this has worked for me and provides a really good packing density. Photos attached.
Dan in Chandler, AZ
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Dave McGuire
Paul Bicknell
David C. Partridge
Michael A. Terrell