Re: Hypothetical question about S-parameter test sets
On 31 December 2012 15:30, Jim Schatzman <james.schatzman@...> wrote: All-
Hypothetically, would it be plausible to build a VNA with custom synthesizer/detectors and the 85047A test set? There seems to be plenty of room inside the box to add the other components. Also, is the 85047A the best choice, assuming that the desired frequency range is 1 MHz to 4 GHz?
Thanks-
Jim What would be your idea - create a unit controlled via USB and have a PC as the interface? Like this sort of thing? That would seem to me the only way you could fit everything inside the box, as you are not going to fit a screen on the test set. The hardware design, testing, software development etc would suggest to me this would be a very long term project. I think trying to base it on something pre-existing like the test set might slow developement more than help. Designing a VNA for 4.2 GHz is not going to be easy. Rather you than me! Dave
|
--- In hp_agilent_equipment@..., "Mike Harmon" <mharmon@...> wrote:
I have a couple of sets of 1/4" hex bits which include Pozidriv bits, but I've been unimpressed with them for the most part. They're fine for infrequent use, but I've found that the alloy is usually pretty soft and the bits don't hold their sharp edges very long. I do a lot of work on Tek scopes and they are almost completely put together with Pozidriv screws.
In addition, the problem with some of the interchangeable-bit drivers is the size of the receptacle on the end of the driver shank which holds the bit. Some of them are nearly 1/2" in diameter. I haven't seen any of them less than 3/8" in diameter.
After getting frustrated multiple times by my inability to get into narrow spaces with the interchangeable-bit driver approach, I went searching for one-piece Pozidriv screwdrivers. Most of them are made by known companies and their quality control and materials appear to be better than the Chinese-made interchangeable-bit sets.
If money is no object, you can buy a complete set of drivers (not bits) from Snap-On for around $100! For mere mortals such as myself, I would suggest you check out K-D Tools, GearWrench, Proto and/or Blackhawk. Google for a local supplier. I found my Blackhawk #1 and #2 Pozi drivers for $7 each at an industrial supply house (Grainger) here in the St. Louis area. Several auto parts houses can get Pozi drivers, but most of them don't carry them in stock.
I believe that Pozi drivers are made in sizes from #0 to #4, but the most common sizes used on electronic gear are #1 and #2. The larger sizes are used primarily on industrial equipment and European cars.
Hope this helps ...
Mike, WB0LDJ
mharmon at att dot net
You can get Pozidriv screwdrivers from Digikey (www.digikey.com). Just search for "Pozidriv". Also, you can get Gearwrench and Wiha screwdrivers on Ebay; just avoid the Vermont American stuff. If you have an Xcelite screwdriver set, there's some Pozidriv bits for it at good price, plus free shipping (Item# 150865657735). McMaster-Carr (www.mcmaster.com) sells Pozidriv screwdrivers and bits as well. Again, search for "Pozidriv" Cheers, Dave M
|
Re: DIY: Repair of HP 8568B Step Attenuators - another question...
Ran across these guys while designing a gas analyzer. They make
all kinds of 0-Rings.
Karl
toggle quoted message
Show quoted text
--- In hp_agilent_equipment@..., Steve Krull <Steve-Krull@...> wrote:
I've got an attenuator for an 8672A that suffers from failed O-rings. In
this case it appears someone used something nasty to try to clean the
spring contacts and attenuator pads and whatever was used dripped down
the nylon plungers and turned all the O-rings to a mushy black paste.
Not a single survivor. Agilent no longer stocks them but provides the
dimensions and material type so I just need to research a source.
Steve
On 12/30/2012 10:16 PM, pianovt wrote:
Hi Jim,
Do not unscrew the solenoids on the top, at least not for now. To see
what's happening, you will have to open the lower part where the RF
action is.
The two SMA connectors have hex-nuts. Remove them. There is thin name
plate that you can now remove. It covers the whole area between the
SMA connectors. It probably has a few glue spots on its other side, so
carefully pry it off without bending the it. Now, you will see a bunch
of socket cap screws. When you remove them, you will be able to
carefully separate the parts and gain access to the attenuator pads
and plungers. The rubber O-rings are on the tiny nylon plungers that
are attached to the gold plated spring contacts. I think there are two
rings on each plunger, one on the RF side and one on the solenoid side.
Vladan
--- In hp_agilent_equipment@...
<mailto:hp_agilent_equipment%40yahoogroups.com>, Jim Schatzman
<james.schatzman@> wrote:
Vladan-
I got the cover off without trouble. By testing I note that when the
middle (40 dB) switch is triggered, the output turns off completely.
As far as I can determine, the plunger is actuated correctly. Moving
it manually also results in the loss of output. The other two switches
(10 and 20 dB) work fine.
I suppose that either the switch contacts are failing or the 40 dB
resistor is open. Apparently both switches and resistors are inside
the two-piece machined steel block. All the RF path seems to be
inside. It would appear that I need to get this apart, but I am not
sure how to. There are quite a few screws attaching the solenoids to
the steel block, but I am not seeing what is holding the steel block
together.
This attenuator has a PC board with several chips on it. I have
noticed before that HP seems to have adopted the philosophy that if 2
chips are good, then 20 must be better. It is a surprisingly
complicated device.
Any advice??
Thanks!
Jim
At 08:45 PM 12/30/2012, you wrote:
Jim,
You will have to pull out the front panel. There are a few
flat-head screws along the front frame (top and bottom, maybe even
sides - don't remember any more). Once you remove them, the front
panel pulls out of the front frame, though it still has a couple of
umbilicals attached. From there, you will see how to get the
attenuator out.
The most common failure has to do with the tiny rubber O-rings on
the plungers. This is all delicate magnifier work. Do not succumb to
the "magnetized housing" myth of repair. The attenuator depends on
magnets for latching. It's just that when the O-ring fails and either
splits or falls off, the mechanism shifts closer to the magnet and the
force of magnetic attraction increases. At that point, the solenoid
(which has nothing wrong with it) no longer can pull the parts away
from the magnet (which also has nothing wrong with it). This is when
some people decide that demagnetizing everything will fix things. If
you have the patience, study the design, it's interesting. The goal
was to use current only when switching a stage is required and then
interrupt all current to the coils as soon as the task is accomplished.
You open the attenuator by removing one of the end caps and sliding
the U-shaped steel cover off. It comes off relatively easily. Don't
try to remove it by prying with screwdrivers.
There are two versions of the attenuators. The older ones are all
electro-mechanical, the newer ones have a p.c. board with some ICs on
them.
Good luck, they can be fixed, but the work requires some patience
and you may have to order no O-rings from Agilent.
Vladan
--- In
<mailto:hp_agilent_equipment%40yahoogroups.com>hp_agilent_equipment@...
<mailto:hp_agilent_equipment%40yahoogroups.com>, Jim Schatzman
<james.schatzman@> wrote:
All-
O.k., I have an 8568B with a bad attenuator (40dB and below are
dead).
My big question is - how do you get access to the attenuator to
take it apart and clean/repair? It seems to be really buried under a
maze of stuff...
Thanks!
Jim
At 01:44 PM 12/27/2012, you wrote:
Thanks a lot of this.
I just managed to get a 8568B that attenuator has some problems
with the 20dB step.
These instructions encourage me to open the attenuator and clean
the pads with isopropyl alcohol. Now it works fine.
I didn't made a testped for it i just cold moved carefully the
solenoids and checked with dg8saq vnwa the attenuator pads. I'm not
sure is the solenoid stuck or is it actually a contact failure.
The instructions how to disaasemble the attenuator was very
accurate and easy to follow.
BR, Jarmo
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
|
Re: Oscilloscopes - analog but with digital capability?
On Mon, 31 Dec 2012 10:56:51 -0500, Chuck Harris <cfharris@...> wrote: J. Forster wrote:
You can play with sampling specs, but 40MS/sec gives a Nyquist limit of 20
MHz.
IMO, you simply cannot trust what you see on the screen of a sampling scope.
-John If by "trust" you mean see things faster than the Nyquist
limit, I fully agree.
However, any competently designed DSO won't allow signals
faster than the Nyquist limit into the sampling stages...
They typically have a brickwall lowpass filter set at some
point significantly below the Nyquist limit to prevent such
aliasing. Could you point out any examples of DSOs that do this? All of the modern ones I am familiar with rely on high real time sample rates and post processing to prevent aliasing if the record length is insufficient. Designing a clean analog filter that tracks the stored sample rate seems like an exercise in futility that would just result in poor impulse response and even worse, a varying impulse response at different decimated sample rates. Older DSO's that had very shallow storage areas frequently
allowed a very sparse representation of the signal to show
on screen. This, when combined with simple vector connect
display methods allowed a variety of interesting Moire patterns
to show on the screen... thus confusing things greatly.
However, modern DSO's don't seem to suffer from that problem. All of my old DSOs (they are all old enough to drink) will operate in equivalent time sampling mode and support peak detection. The lack of the later is the major reason I never picked up the discussed 7D20. The 70MHz bandwidth spec isn't specmanship. It tells you that
the amplifiers will pass a 70MHz signal with 3dB attenuation.
This spec gives you some assurance that the analog stages won't
be distorting the signals being sampled significantly. The 7D20 is a little weird but in equivalent time sampling mode, it can indeed acquire a 70 MHz or faster signal without aliasing using its 40 MS/sec digitizer. Its maximum equivalent time sample rate, limited by its record length, is 2 GS/sec.
|
Re: Oscilloscopes - analog but with digital capability?
On Mon, Dec 31, 2012 at 7:33 AM, J. Forster <jfor@...> wrote: **
You can play with sampling specs, but 40MS/sec gives a Nyquist limit of 20
MHz.
Dave Jones on eevblog reckons you need a sample rate of 10 times the maximum frequency you want to display in single shot mode. Can't say I disagree with him on that. So a sample rate of 40MS/s can realistically only display a 4MHz signal. IMO, you simply cannot trust what you see on the screen of a sampling
scope.
I've had my TDS210 show square waves when undersampling a sinusoid if I forget to set it to peak detect. Orin.
|
Thanks for the information Steve. Hopefully mine will have the 3.6 volt battery seeing as how it has the newer serial number prefix. How old do you figure your battery is to still have that voltage ?
On another note I think I'll get a 3.000 volt reference from voltagestandard.com and build up really carefully a 0.1x and 0.01x Hamon divider to check the 300mv and 30mv ranges. Just as confidence check until I can get it in for calibration. I could in theory check the 30v and 300v ranges by using 0.1x and 0.01x against those voltages adjusting until the division matches the 3.000v reference and then checking the results. So for the lower voltages I would divide by 10 or 100 the precision reference and for anything above the reference I would divide and adjust until it matches the reference and take the remainder. Hope that all makes sense.
3.00v * 0.01 for 30mv
3.00v * 0.1 for 300mv
3.00v * 1 for 3.00v
adj 30v * 0.1 until equal to 3.00v
adj 300v * 0.01 until equal to 3.00v
Thanks,
Jeff
toggle quoted message
Show quoted text
On 12/31/2012 10:20 AM, Steve Krull wrote:
Joe and all,
I just had a quick look inside my 3457A again. Mine has the 3.0 volt
lithium battery, SAFT LX-1634. Obsolete at Agilent, as is the newer
battery. Google was no help either. Mine measures 3.03 volts and there's
no evidence of corrosion so that's good. I couldn't see a date code on
it; probably on the underneath side. I've replaced batteries by
paralleling the existing connections with an appropriate power supply
and then unsoldering the old battery with an isolated-tip iron and
soldering in the new battery. I've also carefully soldered a new battery
in parallel with the old and then clipped out the old one. No problems
with lost data so far.
I'm not sure how the cal numbers increment. I'll have to experiment with
that sometime. Right now I need to repair the 1349D display in my 8757A
so I can get on with a sweeper plug in project, so the volt-nuttery is
on hold for awhile.
Happy New Year to all!
Steve
On 12/30/2012 5:34 PM, J. L. Trantham wrote:
Steve,
Thanks for the data. Mine is also 2703A prefix with REV?:6,0 and
CALNUM?:98. Not a multiple of 34. Would be interesting to see what the
CALNUM increments by after an Agilent CAL.
I, too, need to look at the battery condition. I have not looked at the
manual regarding replacing the battery. Has anyone done that without
losing
the CAL Constants?
Joe
-----Original Message-----
From: hp_agilent_equipment@...
<mailto:hp_agilent_equipment%40yahoogroups.com>
<mailto:hp_agilent_equipment%40yahoogroups.com>
[mailto:hp_agilent_equipment@... <mailto:hp_agilent_equipment%40yahoogroups.com>
<mailto:hp_agilent_equipment%40yahoogroups.com>] On Behalf Of Steve
Sent: Sunday, December 30, 2012 4:14 PM
To: hp_agilent_equipment@... <mailto:hp_agilent_equipment%40yahoogroups.com>
<mailto:hp_agilent_equipment%40yahoogroups.com>
Subject: Re: [hp_agilent_equipment] 3457a on the way
It would be interesting to see if a newer rev is out there. My 3457A
is s.n.
prefix 2703, with rev 6,0 and option 0, CALNUM=34. I wonder if that's a
default number for anything less than a full cal at Agilent? The last
calibration was at least 6 years ago and performed by what was then Boeing
Military Airplane Company's metrology lab. I need to open it up and check
the battery condition.
Steve
|
Re: Oscilloscopes - analog but with digital capability?
Speaking of old scopes, the first digital scope I got circa 1986 was a Tek with a sample rate around 20 or 50 Msps, bandwidth 100 or 200 MHz. For repetitive signals it dithered the sample clock to reconstruct signals well above the Nyquist frequency over many cycles. It couldn't see fast single event signals, of course.
It also had a pure analog mode. For the time, it was a pretty decent instrument.Unfortunately, I've long forgotten the model number, but it looked like a 24xx series.
Erich
toggle quoted message
Show quoted text
--- In hp_agilent_equipment@..., Chuck Harris <cfharris@...> wrote:
Hi Peter,
As I said, "any competently designed DSO". An analog scope gives
you the full vertical bandwidth regardless of the timebase setting.
A competently designed DSO should also.
You can be a bit flexible about that requirement, though. If the
aliasing effects are too fast to see at a particular timebase
setting, it would be ok to slow the sample rate until they are
only marginally too fast to see.
-Chuck Harris
Peter Gottlieb wrote:
But it's not just filtering above the Nyquist. There are other ways a sampling
digital scope can give you a wrong picture of reality. If all of these scopes
ran their digitizers constantly at full rate, watched for envelope effects and
so forth they would go a long way towards eliminating these unwanted erroneous
displays.
Peter
On 12/31/2012 10:56 AM, Chuck Harris wrote:
If by "trust" you mean see things faster than the Nyquist
limit, I fully agree.
|
Re: DIY: Repair of HP 8568B Step Attenuators - another question...
I've got an attenuator for an 8672A that suffers from failed O-rings. In
this case it appears someone used something nasty to try to clean the
spring contacts and attenuator pads and whatever was used dripped down
the nylon plungers and turned all the O-rings to a mushy black paste.
Not a single survivor. Agilent no longer stocks them but provides the
dimensions and material type so I just need to research a source.
Steve
toggle quoted message
Show quoted text
On 12/30/2012 10:16 PM, pianovt wrote:
Hi Jim,
Do not unscrew the solenoids on the top, at least not for now. To see
what's happening, you will have to open the lower part where the RF
action is.
The two SMA connectors have hex-nuts. Remove them. There is thin name
plate that you can now remove. It covers the whole area between the
SMA connectors. It probably has a few glue spots on its other side, so
carefully pry it off without bending the it. Now, you will see a bunch
of socket cap screws. When you remove them, you will be able to
carefully separate the parts and gain access to the attenuator pads
and plungers. The rubber O-rings are on the tiny nylon plungers that
are attached to the gold plated spring contacts. I think there are two
rings on each plunger, one on the RF side and one on the solenoid side.
Vladan
--- In hp_agilent_equipment@...
<mailto:hp_agilent_equipment%40yahoogroups.com>, Jim Schatzman
<james.schatzman@...> wrote:
Vladan-
I got the cover off without trouble. By testing I note that when the
middle (40 dB) switch is triggered, the output turns off completely.
As far as I can determine, the plunger is actuated correctly. Moving
it manually also results in the loss of output. The other two switches
(10 and 20 dB) work fine.
I suppose that either the switch contacts are failing or the 40 dB
resistor is open. Apparently both switches and resistors are inside
the two-piece machined steel block. All the RF path seems to be
inside. It would appear that I need to get this apart, but I am not
sure how to. There are quite a few screws attaching the solenoids to
the steel block, but I am not seeing what is holding the steel block
together.
This attenuator has a PC board with several chips on it. I have
noticed before that HP seems to have adopted the philosophy that if 2
chips are good, then 20 must be better. It is a surprisingly
complicated device.
Any advice??
Thanks!
Jim
At 08:45 PM 12/30/2012, you wrote:
Jim,
You will have to pull out the front panel. There are a few
flat-head screws along the front frame (top and bottom, maybe even
sides - don't remember any more). Once you remove them, the front
panel pulls out of the front frame, though it still has a couple of
umbilicals attached. From there, you will see how to get the
attenuator out.
The most common failure has to do with the tiny rubber O-rings on
the plungers. This is all delicate magnifier work. Do not succumb to
the "magnetized housing" myth of repair. The attenuator depends on
magnets for latching. It's just that when the O-ring fails and either
splits or falls off, the mechanism shifts closer to the magnet and the
force of magnetic attraction increases. At that point, the solenoid
(which has nothing wrong with it) no longer can pull the parts away
from the magnet (which also has nothing wrong with it). This is when
some people decide that demagnetizing everything will fix things. If
you have the patience, study the design, it's interesting. The goal
was to use current only when switching a stage is required and then
interrupt all current to the coils as soon as the task is accomplished.
You open the attenuator by removing one of the end caps and sliding
the U-shaped steel cover off. It comes off relatively easily. Don't
try to remove it by prying with screwdrivers.
There are two versions of the attenuators. The older ones are all
electro-mechanical, the newer ones have a p.c. board with some ICs on
them.
Good luck, they can be fixed, but the work requires some patience
and you may have to order no O-rings from Agilent.
Vladan
--- In
<mailto:hp_agilent_equipment%40yahoogroups.com>hp_agilent_equipment@...
<mailto:hp_agilent_equipment%40yahoogroups.com>, Jim Schatzman
<james.schatzman@> wrote:
All-
O.k., I have an 8568B with a bad attenuator (40dB and below are
dead).
My big question is - how do you get access to the attenuator to
take it apart and clean/repair? It seems to be really buried under a
maze of stuff...
Thanks!
Jim
At 01:44 PM 12/27/2012, you wrote:
Thanks a lot of this.
I just managed to get a 8568B that attenuator has some problems
with the 20dB step.
These instructions encourage me to open the attenuator and clean
the pads with isopropyl alcohol. Now it works fine.
I didn't made a testped for it i just cold moved carefully the
solenoids and checked with dg8saq vnwa the attenuator pads. I'm not
sure is the solenoid stuck or is it actually a contact failure.
The instructions how to disaasemble the attenuator was very
accurate and easy to follow.
BR, Jarmo
|
Joe and all,
I just had a quick look inside my 3457A again. Mine has the 3.0 volt
lithium battery, SAFT LX-1634. Obsolete at Agilent, as is the newer
battery. Google was no help either. Mine measures 3.03 volts and there's
no evidence of corrosion so that's good. I couldn't see a date code on
it; probably on the underneath side. I've replaced batteries by
paralleling the existing connections with an appropriate power supply
and then unsoldering the old battery with an isolated-tip iron and
soldering in the new battery. I've also carefully soldered a new battery
in parallel with the old and then clipped out the old one. No problems
with lost data so far.
I'm not sure how the cal numbers increment. I'll have to experiment with
that sometime. Right now I need to repair the 1349D display in my 8757A
so I can get on with a sweeper plug in project, so the volt-nuttery is
on hold for awhile.
Happy New Year to all!
Steve
toggle quoted message
Show quoted text
On 12/30/2012 5:34 PM, J. L. Trantham wrote:
Steve,
Thanks for the data. Mine is also 2703A prefix with REV?:6,0 and
CALNUM?:98. Not a multiple of 34. Would be interesting to see what the
CALNUM increments by after an Agilent CAL.
I, too, need to look at the battery condition. I have not looked at the
manual regarding replacing the battery. Has anyone done that without
losing
the CAL Constants?
Joe
-----Original Message-----
From: hp_agilent_equipment@...
<mailto:hp_agilent_equipment%40yahoogroups.com>
[mailto:hp_agilent_equipment@...
<mailto:hp_agilent_equipment%40yahoogroups.com>] On Behalf Of Steve
Sent: Sunday, December 30, 2012 4:14 PM
To: hp_agilent_equipment@...
<mailto:hp_agilent_equipment%40yahoogroups.com>
Subject: Re: [hp_agilent_equipment] 3457a on the way
It would be interesting to see if a newer rev is out there. My 3457A
is s.n.
prefix 2703, with rev 6,0 and option 0, CALNUM=34. I wonder if that's a
default number for anything less than a full cal at Agilent? The last
calibration was at least 6 years ago and performed by what was then Boeing
Military Airplane Company's metrology lab. I need to open it up and check
the battery condition.
Steve
On Dec 29, 2012, at 8:08 PM, "J. L. Trantham" <jltran@...
<mailto:jltran%40att.net>
<mailto:jltran%40att.net> > wrote:
If the 'SELF TEST OK' message appears, there is no need to make any
'adjustments'. Just do the 'front panel CAL' if needed.
As I said, I would check it out, assume it is the best instrument in your
collection, send it to Agilent for CAL and see what you get.
I would appreciate knowing what 'REV?' and 'OPT?' says when you get a
chance. 'CALNUM?' would be interesting as well.
In the 3458A, the firmware is in an EPROM (6 EPROM's for the older units)
and can be removed, a socket placed, and easily upgraded by purchasing the
latest pre-programmed EPROM (or EPROM's for the older units) from Agilent.
The only problem is they have a $50 minimum for this $18 part for the later
units.
My wife thinks I am going to appear on an episode of 'Hoarders'.
Joe
-----Original Message-----
From: hp_agilent_equipment@... <mailto:hp_agilent_equipment%40yahoogroups.com>
<mailto:hp_agilent_equipment%40yahoogroups.com>
[mailto:hp_agilent_equipment@... <mailto:hp_agilent_equipment%40yahoogroups.com>
<mailto:hp_agilent_equipment%40yahoogroups.com> ] On Behalf Of Jeff
Machesky
Sent: Saturday, December 29, 2012 8:01 PM
To: hp_agilent_equipment@... <mailto:hp_agilent_equipment%40yahoogroups.com>
<mailto:hp_agilent_equipment%40yahoogroups.com>
Subject: Re: [hp_agilent_equipment] 3457a on the way
Wow, lots of replies all of a sudden. I'm already prepping the wife for
the $200 + price tag of calibration. Funny how when I was single I would
have about $800 in cash in my wallet at all times and now I beg for 20
bucks, Hmm. Sad part is I make about 4 times the money. In any event
I've not received to much feedback on the "Self Test OK" message the
seller had posted. Any comments? I'm too much of a skeptic when it comes
to eBay purchases. It's just a convenient place to purchase such goods.
Any feedback would be appreciated as to possible pitfalls regarding this
device. I like to prep for issues rather then build myself up for
failure. What do they say...it's better to be pleasantly surprised then
let down.
Thanks,
Jeff
On 12/29/2012 5:40 PM, J. L. Trantham wrote:
According to the manual, there are only two 'adjustments' that can be
made
on a 3457A, Input Offset Amplifier adjustment and AC Converter
Frequency
Response, both needed only if there is a 'HARDWARE ERR' failure
message
after 'TEST' is selected and then only if it is a specific
'AUXERR' or
16 or
256 is seen. Otherwise, all the calibrations are done from the front
panel
with specific inputs from the front panel.
The CALNUM? is incremented by 'several digits' with a 'complete
calibration', one for each calibration point entered, per the manual.
Interestingly, when I sent my two 3458A's to Agilent for calibration,
the
CALNUM incremented by only 1. However, when I calibrated one of them
before
sending it to Agilent, (since I lost the data in the DALLAS CALRAM
chip that
I was removing) the CALNUM went from 1 to something like 34 or
something. I
don't recall. It seems that if you have the appropriate software to
run the
complete calibration protocol, it only increments by '1' instead of by
all
the data points entered. Such software exists for the 3457A but I have
never seen it available 'on theBay'. I suspect Agilent would have that
software and equipment to do that calibration and, thus, an Agilent
calibration may only increment the CALNUM? by 1.
When getting an Agilent calibration of the 3458A, you get 'As
Received' and
'As Completed' data. Very helpful to me in that the only two points my
'House CAL' of the one 3458A failed were the two 'midrange' AC Voltage
values. All else 'PASSED'.
I agree with Dave. If it's HP/Agilent, I prefer Agilent to do the CAL.
If
it's Solartron, I prefer AMETEK (Solartron), etc.
I believe that having some 'basic' professionally calibrated
instruments
(DMM's, Noise Sources, Power Sensors, Frequency Standards (unless you
have a
GPSDO, CS Standard, etc.) etc.), that you can then use as 'transfer
standards' to do your own 'in house' calibration of other instruments,
is
very important if you want to set up a reliable workshop.
Of course, you will also need a 'stable' source of the various
signals
that
you will use to be 'measured' by the various 'DUT's', such as
resistance,
voltage, current, frequency, etc. The 3458A is relatively easy to
calibrate, requiring only 10.000000 VDC, 10000.000 ohms, and some AC
voltage
at various frequencies, IIRC. I have never CAL'd a 3457A but the
3478A
is a
multi-step process.
This whole thing can become very 'addictive'. Be careful.
Joe
-----Original Message-----
From: hp_agilent_equipment@...
<mailto:hp_agilent_equipment%40yahoogroups.com>
<mailto:hp_agilent_equipment%40yahoogroups.com>
<mailto:hp_agilent_equipment%40yahoogroups.com>
[mailto:hp_agilent_equipment@...
<mailto:hp_agilent_equipment%40yahoogroups.com>
<mailto:hp_agilent_equipment%40yahoogroups.com>
<mailto:hp_agilent_equipment%40yahoogroups.com>] On Behalf Of David
Kirkby
Sent: Saturday, December 29, 2012 5:53 PM
To: hp_agilent_equipment@...
<mailto:hp_agilent_equipment%40yahoogroups.com>
<mailto:hp_agilent_equipment%40yahoogroups.com>
<mailto:hp_agilent_equipment%40yahoogroups.com>
Subject: Re: [hp_agilent_equipment] 3457a on the way
On 29 December 2012 20:01, Jeff Machesky <jeff@...
<mailto:jeff%40codebest.com>
<mailto:jeff%40codebest.com>
<mailto:jeff%40codebest.com>
<mailto:jeff%40codebest.com> > wrote:
Thanks Dave, I actually have watched those videos. Bit drawn out
like
most of his videos..but still good. Too much detail is not always a
bad
thing. I thought the bit showing the noise on the DVM was a bit silly when it
was connected to a DC power supply.
As for the 3457A, if it works I plan on getting it calibrated by
Agilent
within the year. From what I understand it's about a $200 US
investment.
The meter was last calibrated in '98, so I'll be curious to see how
accurate it is when I get it. I think the calibration service you chose might dictate whether you
get data about the condition when sent.
When I send mine in for cal, I'd like to know what was out and by how
much. But I'm not going to pay extra for a calibration service that
provides that. As far as I'm concerned, if Agilent calibrate it, then
it is OK. For me personally, it makes no difference whatsoever if it
has ISO, NIST or whatever calibration. But I'd prefer Agilent to
someone else.
I have calibration certificate here for an Agilent VNA calibration
kit. It was done by a calibration house in the USA. But from what I
can gather from reading the documentation, the equipment to calibrate
them is not available commerically. So it makes me wonder how a lab
can calibrate a cal kit, when the equipment to do it can't be bought.
I suspect there is a fairly cosy realationship between some test
equipment dealers and calibration facilities.
I plan on purchasing some
voltage references from the well known site as a basic test of the
3457A. I may even calibrate it based on those references if it's way
out
and later getting it NIST traceable calibrated. I don't know if there are pots in there you can adjust with a trimmer,
or if it is all done electronically. You might find it is impossible
to calibrate yourself.
I never had any reason to look inside mine.
Dave
------------------------------------
Yahoo! Groups Links
|
Re: Oscilloscopes - analog but with digital capability?
Hi Peter,
As I said, "any competently designed DSO". An analog scope gives
you the full vertical bandwidth regardless of the timebase setting.
A competently designed DSO should also.
You can be a bit flexible about that requirement, though. If the
aliasing effects are too fast to see at a particular timebase
setting, it would be ok to slow the sample rate until they are
only marginally too fast to see.
-Chuck Harris
Peter Gottlieb wrote:
toggle quoted message
Show quoted text
But it's not just filtering above the Nyquist. There are other ways a sampling
digital scope can give you a wrong picture of reality. If all of these scopes
ran their digitizers constantly at full rate, watched for envelope effects and
so forth they would go a long way towards eliminating these unwanted erroneous
displays.
Peter
On 12/31/2012 10:56 AM, Chuck Harris wrote:
If by "trust" you mean see things faster than the Nyquist
limit, I fully agree.
|
Re: Oscilloscopes - analog but with digital capability?
I hadn't thought of that. I will swab things down with some De-oxit to help clean things up.
Peter
toggle quoted message
Show quoted text
On 12/31/2012 11:41 AM, Chuck Harris wrote:
Hi Peter,
Sometimes, on an instrument that has been in storage for a long
while, corrosion on the input BNC/N connector can cause for a round
of strange readings... non-linear junctions, and all that.
Be sure that the BNC's on the cables, and on the instrument are
clean and lubed with a little cramolin, or other contact cleaner.
-Chuck Harris
Peter Gottlieb wrote:
So I'm finally getting to unpack all my gear and set up a lab again. As part of
setting up my bench I am doing basic functionality checks on the instruments I
intend to use. One is a "straightforward" HP 5335A counter. Hooked it up to a
HP signal generator putting out a nice 5 volt sine wave at 1000 Hz. What does
the counter tell me? Around 1800 Hz and unsteady. Analog scope tells me it
looks great, nice and clean... Try it again on the counter and 1000 Hz on the
nose and rock solid. I've found in the past that it is very easy to get the
second harmonic reading on a counter as well. And DVMs, forget about it, some
read AC riding on DC very strangely, or if you have a non-true-RMS meter...
There are many cases where you need to understand what you are looking at and
what you are expecting. You need this to sanity-check the instrument as well as
to understand what you need to do to verify your reading. Yes, analog scopes
can show you a very true picture of what's happening but you can easily miss
some massive fast/short transients too.
To get the most from this gear you need to understand each instrument and what
it's limitations are. You need to know your tools.
Now what's up with that 5335A and the strange result I am now unable to
duplicate? ;-)
Now back to work... --------------------------------------------------------------------------------
No virus found in this message.
Checked by AVG - www.avg.com <>
Version: 10.0.1430 / Virus Database: 2637/5499 - Release Date: 12/31/12
|
Re: Oscilloscopes - analog but with digital capability?
But it's not just filtering above the Nyquist. There are other ways a sampling digital scope can give you a wrong picture of reality. If all of these scopes ran their digitizers constantly at full rate, watched for envelope effects and so forth they would go a long way towards eliminating these unwanted erroneous displays.
Peter
toggle quoted message
Show quoted text
On 12/31/2012 10:56 AM, Chuck Harris wrote:
If by "trust" you mean see things faster than the Nyquist
limit, I fully agree.
However, any competently designed DSO won't allow signals
faster than the Nyquist limit into the sampling stages...
They typically have a brickwall lowpass filter set at some
point significantly below the Nyquist limit to prevent such
aliasing.
Older DSO's that had very shallow storage areas frequently
allowed a very sparse representation of the signal to show
on screen. This, when combined with simple vector connect
display methods allowed a variety of interesting Moire patterns
to show on the screen... thus confusing things greatly.
However, modern DSO's don't seem to suffer from that problem.
The 70MHz bandwidth spec isn't specmanship. It tells you that
the amplifiers will pass a 70MHz signal with 3dB attenuation.
This spec gives you some assurance that the analog stages won't
be distorting the signals being sampled significantly.
-Chuck Harris
J. Forster wrote:
You can play with sampling specs, but 40MS/sec gives a Nyquist limit of 20
MHz.
IMO, you simply cannot trust what you see on the screen of a sampling scope.
-John
=========== --------------------------------------------------------------------------------
No virus found in this message.
Checked by AVG - www.avg.com <>
Version: 10.0.1430 / Virus Database: 2637/5499 - Release Date: 12/31/12
|
Re: Oscilloscopes - analog but with digital capability?
Well, that's why I have to have so many different scopes ;-)
toggle quoted message
Show quoted text
On 12/31/2012 10:56 AM, J. Forster wrote:
Try looking for abnormalities on a LORAN-A pulse, for example... a few 10s
of uS of 2 MHz every few 10s of mS, or a disk drive data stream
abnormality.
-John
=================
So I'm finally getting to unpack all my gear and set up a lab again. As
part of
setting up my bench I am doing basic functionality checks on the
instruments I
intend to use. One is a "straightforward" HP 5335A counter. Hooked it up
to a
HP signal generator putting out a nice 5 volt sine wave at 1000 Hz. What
does
the counter tell me? Around 1800 Hz and unsteady. Analog scope tells me
it
looks great, nice and clean... Try it again on the counter and 1000 Hz on
the
nose and rock solid. I've found in the past that it is very easy to get
the
second harmonic reading on a counter as well. And DVMs, forget about it,
some
read AC riding on DC very strangely, or if you have a non-true-RMS
meter...
There are many cases where you need to understand what you are looking at
and
what you are expecting. You need this to sanity-check the instrument as
well as
to understand what you need to do to verify your reading. Yes, analog
scopes
can show you a very true picture of what's happening but you can easily
miss
some massive fast/short transients too.
To get the most from this gear you need to understand each instrument and
what
it's limitations are. You need to know your tools.
Now what's up with that 5335A and the strange result I am now unable to
duplicate? ;-)
Now back to work...
On 12/31/2012 10:33 AM, J. Forster wrote:
IMO, you simply cannot trust what you see on the screen of a sampling
scope.
-John
===========
--------------------------------------------------------------------------------
No virus found in this message.
Checked by AVG - www.avg.com <>
Version: 10.0.1430 / Virus Database: 2637/5499 - Release Date: 12/31/12
|
Re: Oscilloscopes - analog but with digital capability?
Hi Peter,
Sometimes, on an instrument that has been in storage for a long
while, corrosion on the input BNC/N connector can cause for a round
of strange readings... non-linear junctions, and all that.
Be sure that the BNC's on the cables, and on the instrument are
clean and lubed with a little cramolin, or other contact cleaner.
-Chuck Harris
Peter Gottlieb wrote:
toggle quoted message
Show quoted text
So I'm finally getting to unpack all my gear and set up a lab again. As part of
setting up my bench I am doing basic functionality checks on the instruments I
intend to use. One is a "straightforward" HP 5335A counter. Hooked it up to a
HP signal generator putting out a nice 5 volt sine wave at 1000 Hz. What does
the counter tell me? Around 1800 Hz and unsteady. Analog scope tells me it
looks great, nice and clean... Try it again on the counter and 1000 Hz on the
nose and rock solid. I've found in the past that it is very easy to get the
second harmonic reading on a counter as well. And DVMs, forget about it, some
read AC riding on DC very strangely, or if you have a non-true-RMS meter...
There are many cases where you need to understand what you are looking at and
what you are expecting. You need this to sanity-check the instrument as well as
to understand what you need to do to verify your reading. Yes, analog scopes
can show you a very true picture of what's happening but you can easily miss
some massive fast/short transients too.
To get the most from this gear you need to understand each instrument and what
it's limitations are. You need to know your tools.
Now what's up with that 5335A and the strange result I am now unable to
duplicate? ;-)
Now back to work...
|
Re: Oscilloscopes - analog but with digital capability?
If by "trust" you mean see things faster than the Nyquist
limit, I fully agree.
However, any competently designed DSO won't allow signals
faster than the Nyquist limit into the sampling stages...
They typically have a brickwall lowpass filter set at some
point significantly below the Nyquist limit to prevent such
aliasing.
Older DSO's that had very shallow storage areas frequently
allowed a very sparse representation of the signal to show
on screen. This, when combined with simple vector connect
display methods allowed a variety of interesting Moire patterns
to show on the screen... thus confusing things greatly.
However, modern DSO's don't seem to suffer from that problem.
The 70MHz bandwidth spec isn't specmanship. It tells you that
the amplifiers will pass a 70MHz signal with 3dB attenuation.
This spec gives you some assurance that the analog stages won't
be distorting the signals being sampled significantly.
-Chuck Harris
J. Forster wrote:
toggle quoted message
Show quoted text
You can play with sampling specs, but 40MS/sec gives a Nyquist limit of 20
MHz.
IMO, you simply cannot trust what you see on the screen of a sampling scope.
-John
===========
|
Re: Oscilloscopes - analog but with digital capability?
Try looking for abnormalities on a LORAN-A pulse, for example... a few 10s
of uS of 2 MHz every few 10s of mS, or a disk drive data stream
abnormality.
-John
=================
toggle quoted message
Show quoted text
So I'm finally getting to unpack all my gear and set up a lab again. As
part of
setting up my bench I am doing basic functionality checks on the
instruments I
intend to use. One is a "straightforward" HP 5335A counter. Hooked it up
to a
HP signal generator putting out a nice 5 volt sine wave at 1000 Hz. What
does
the counter tell me? Around 1800 Hz and unsteady. Analog scope tells me
it
looks great, nice and clean... Try it again on the counter and 1000 Hz on
the
nose and rock solid. I've found in the past that it is very easy to get
the
second harmonic reading on a counter as well. And DVMs, forget about it,
some
read AC riding on DC very strangely, or if you have a non-true-RMS
meter...
There are many cases where you need to understand what you are looking at
and
what you are expecting. You need this to sanity-check the instrument as
well as
to understand what you need to do to verify your reading. Yes, analog
scopes
can show you a very true picture of what's happening but you can easily
miss
some massive fast/short transients too.
To get the most from this gear you need to understand each instrument and
what
it's limitations are. You need to know your tools.
Now what's up with that 5335A and the strange result I am now unable to
duplicate? ;-)
Now back to work...
On 12/31/2012 10:33 AM, J. Forster wrote:
IMO, you simply cannot trust what you see on the screen of a sampling
scope.
-John
===========
|
Re: Oscilloscopes - analog but with digital capability?
So I'm finally getting to unpack all my gear and set up a lab again. As part of setting up my bench I am doing basic functionality checks on the instruments I intend to use. One is a "straightforward" HP 5335A counter. Hooked it up to a HP signal generator putting out a nice 5 volt sine wave at 1000 Hz. What does the counter tell me? Around 1800 Hz and unsteady. Analog scope tells me it looks great, nice and clean... Try it again on the counter and 1000 Hz on the nose and rock solid. I've found in the past that it is very easy to get the second harmonic reading on a counter as well. And DVMs, forget about it, some read AC riding on DC very strangely, or if you have a non-true-RMS meter...
There are many cases where you need to understand what you are looking at and what you are expecting. You need this to sanity-check the instrument as well as to understand what you need to do to verify your reading. Yes, analog scopes can show you a very true picture of what's happening but you can easily miss some massive fast/short transients too.
To get the most from this gear you need to understand each instrument and what it's limitations are. You need to know your tools.
Now what's up with that 5335A and the strange result I am now unable to duplicate? ;-)
Now back to work...
toggle quoted message
Show quoted text
On 12/31/2012 10:33 AM, J. Forster wrote:
IMO, you simply cannot trust what you see on the screen of a sampling scope.
-John
===========
|
I am no fan of Sears because tgey really screwed me over on a socket set,
but they do sell a pair of screwdriver sets that use hex bits. There are
two bit sets and a common handle, totalling 64 bits, in two plastic
blocks. The handle has a P/N 49099.
FWIW,
-John
=============
toggle quoted message
Show quoted text
I was lucky and got a set of Pozi bits in the local Sears (#26493). Looks
like they are out of them now - they are quoting 13 to 15 days for store
pickup.
Orin.
On Sun, Dec 30, 2012 at 9:31 PM, Richard Knoppow
<dickburk@...>wrote:
**
----- Original Message -----
From: "bownes" <bownes@...>
To: <hp_agilent_equipment@...>
Sent: Sunday, December 30, 2012 9:03 PM
Subject: [hp_agilent_equipment] Pozi-Drive bits
I know this has come up many times in the past so when I
stumbled upon PoziDrive driver bits today in the HomeDepot
I thought I would pass on the tip (Pardon the pun please).
There are two driver bit sets, a 29 piece, and a 30 piece,
both are three dollars apiece. Between the two there are
bits sized from PZ0 to PZ3, with some duplication. I
thought that $6 wasn't a bad price to have all these in
the tool box.
They are in private labeled assortments sold under the HD
brand.
Bob
Thank you very much Bob. When I searched around for
Pozidriv screwdrivers I discovered no one locally seemed to
have them and some places never heard of them. I wound up
buying them from Amazon. These are _much_ cheaper and one
hopes of decent quality.
--
Richard Knoppow
Los Angeles
WB6KBL
dickburk@...
------------------------------------
Yahoo! Groups Links
|
Re: Oscilloscopes - analog but with digital capability?
You can play with sampling specs, but 40MS/sec gives a Nyquist limit of 20
MHz.
IMO, you simply cannot trust what you see on the screen of a sampling scope.
-John
===========
toggle quoted message
Show quoted text
Are you sure about the 70 MHz on the 7D20. I doubt that it was that good
one shot. The specifications say 70 MHz bandwidth and simultaneous sampling of
40 MS/sec on each channel. I have heard that the bandwidth could be
significantly higher on some units.
|
Re: Hypothetical question about S-parameter test sets
All-
Hypothetically, would it be plausible to build a VNA with custom synthesizer/detectors and the 85047A test set? There seems to be plenty of room inside the box to add the other components. Also, is the 85047A the best choice, assuming that the desired frequency range is 1 MHz to 4 GHz?
Thanks-
Jim
|
David Hess