Scoping small current pulses with Tektronix TM500 series?

Guest
Hi Group,

I am looking for a way to measure the waveform of a current pulse, on
the other of 1-10uA, and with a rise time of ~1us, without disturbing
the 0.5V DC signal that is forced on this node. I was told this is
possible with a combination of Tektronix TM502A (power module
mainframe), AM503B (current probe amplifier module with digital scale
readout), and an oscilloscope. I was wondering if anyone here has
experience with such measurements using this set up, or may suggest a
better method. From reading the AM503B manual I get the impression that
it does not have uA resolution, but then I could have missed soemthing.

Many thanks.

Dan
 
laladong@hotmail.com wrote in
news:1154737386.036397.74930@i3g2000cwc.googlegroups.com:

Hi Group,

I am looking for a way to measure the waveform of a current pulse, on
the other of 1-10uA, and with a rise time of ~1us, without disturbing
the 0.5V DC signal that is forced on this node. I was told this is
possible with a combination of Tektronix TM502A (power module
mainframe), AM503B (current probe amplifier module with digital scale
readout), and an oscilloscope. I was wondering if anyone here has
experience with such measurements using this set up, or may suggest a
better method. From reading the AM503B manual I get the impression that
it does not have uA resolution, but then I could have missed soemthing.

Many thanks.

Dan
Click to expand...
Make/insert a small 10 turn wire loop to place the A6302 probe around;that
multiplies the current sensitivity by 10.
You may not disturb the signal enough to matter,it depends on your circuit.

IIRC,the highest sensitivity of the AM503/A6302 is 1 ma/div.

Of course,you can also change the display scope's Volts/div setting to
magnify your resolution.(there are limits,though)
And AC couple the scope,or use one with an adjustable DC offset,like a
7A13/7K combo.

IIRC,that's set at 50mv/div,50ohm inputZ.
AM503 system BW is 50 Mhz,IIRC.


BTW,I used to repair/calibrate AM503 systems at TEK-Orlando.
(before they shut all the field offices down)

--
Jim Yanik
jyanik
at
kua.net
 
"Jim Yanik" <jyanik@abuse.gov> a écrit dans le message de
news:Xns9815D1ACF393Ajyanikkuanet@129.250.170.83...
laladong@hotmail.com wrote in
news:1154737386.036397.74930@i3g2000cwc.googlegroups.com:

Hi Group,

I am looking for a way to measure the waveform of a current pulse, on
the other of 1-10uA, and with a rise time of ~1us, without disturbing
the 0.5V DC signal that is forced on this node. I was told this is
possible with a combination of Tektronix TM502A (power module
mainframe), AM503B (current probe amplifier module with digital scale
readout), and an oscilloscope. I was wondering if anyone here has
experience with such measurements using this set up, or may suggest a
better method. From reading the AM503B manual I get the impression that
it does not have uA resolution, but then I could have missed soemthing.

Many thanks.

Dan



Make/insert a small 10 turn wire loop to place the A6302 probe around;that
multiplies the current sensitivity by 10.
You may not disturb the signal enough to matter,it depends on your
circuit.

IIRC,the highest sensitivity of the AM503/A6302 is 1 ma/div.

Of course,you can also change the display scope's Volts/div setting to
magnify your resolution.(there are limits,though)
And AC couple the scope,or use one with an adjustable DC offset,like a
7A13/7K combo.

IIRC,that's set at 50mv/div,50ohm inputZ.
AM503 system BW is 50 Mhz,IIRC.


BTW,I used to repair/calibrate AM503 systems at TEK-Orlando.
(before they shut all the field offices down)
Click to expand...
Glad you said that.
I just got hold of an AM503 that had been severely "adjusted" to the point
its sensitivity was off by more than 25%.
I went through all the cal procedure, but got a bit confused by the 'adjust
until getting good results' for the HF compensation resistors and cap.

Do you have any good hint about this?


--
Thanks,
Fred.
 
Jim,

Please excuse me for taking this opportunity to consult you.

I have a copuple of AM503's with attenuator issues.
The contact fingers are loose efter the nylon? fasteners have
broken/cracked.

Is this a common problem or am I just unlucky?
What is the best way to fix this?

Thanks,
Anders J






"Jim Yanik" <jyanik@abuse.gov> skrev i meddelandet
news:Xns9815D1ACF393Ajyanikkuanet@129.250.170.83...
laladong@hotmail.com wrote in
news:1154737386.036397.74930@i3g2000cwc.googlegroups.com:

Hi Group,

I am looking for a way to measure the waveform of a current pulse, on
the other of 1-10uA, and with a rise time of ~1us, without disturbing
the 0.5V DC signal that is forced on this node. I was told this is
possible with a combination of Tektronix TM502A (power module
mainframe), AM503B (current probe amplifier module with digital scale
readout), and an oscilloscope. I was wondering if anyone here has
experience with such measurements using this set up, or may suggest a
better method. From reading the AM503B manual I get the impression that
it does not have uA resolution, but then I could have missed soemthing.

Many thanks.

Dan



Make/insert a small 10 turn wire loop to place the A6302 probe around;that
multiplies the current sensitivity by 10.
You may not disturb the signal enough to matter,it depends on your
circuit.

IIRC,the highest sensitivity of the AM503/A6302 is 1 ma/div.

Of course,you can also change the display scope's Volts/div setting to
magnify your resolution.(there are limits,though)
And AC couple the scope,or use one with an adjustable DC offset,like a
7A13/7K combo.

IIRC,that's set at 50mv/div,50ohm inputZ.
AM503 system BW is 50 Mhz,IIRC.


BTW,I used to repair/calibrate AM503 systems at TEK-Orlando.
(before they shut all the field offices down)

--
Jim Yanik
jyanik
at
kua.net
Click to expand...
 
"Anders Johansson" <anders.nospam.johansson@fifo.se> wrote in
news:2ahBg.12055$E02.4275@newsb.telia.net:

Jim,

Please excuse me for taking this opportunity to consult you.

I have a copuple of AM503's with attenuator issues.
The contact fingers are loose efter the nylon? fasteners have
broken/cracked.

Is this a common problem or am I just unlucky?
What is the best way to fix this?

Thanks,
Anders J
Click to expand...

I believe you are talking about TEK's HF cam switch contacts.
Yes,with age,the white plastic degrades and the gold-plated contact fingers
fall off the spring portion. You will have to find some other TEK
instrument with intact contacts you can cannabalize for your AM503.
TEK used to offer a complete kit for this,but it's long out of
production/stock. The new contacts were bolted down using 2-56 bolts and
nuts,IIRC.
Begin cannabalization by removing the solder at the rivet end,and use a
small 1/8" drill to remove the rivet by reaming off the flared end of the
rivet.then push out the rivet,the contact may come right along with it.
I believe the contacts are used on both sides of the PCB,too.

I suppose you could try wicking some thin cyanoacrylate glue into the loose
contact where the plastic holds the contact fingers,but don't get any on
the fingers!! Maybe run the superglue down a needle or fine wire to where
you want it.I've not tried that,though.


--
Jim Yanik
jyanik
at
kua.net
 
"Fred Bartoli"
<fred._canxxxel_this_bartoli@RemoveThatAlso_free.fr_AndThisToo> wrote in
news:44d4d86a$0$13532$626a54ce@news.free.fr:

"Jim Yanik" <jyanik@abuse.gov> a écrit dans le message de
news:Xns9815D1ACF393Ajyanikkuanet@129.250.170.83...
laladong@hotmail.com wrote in
news:1154737386.036397.74930@i3g2000cwc.googlegroups.com:

Hi Group,

I am looking for a way to measure the waveform of a current pulse,
on the other of 1-10uA, and with a rise time of ~1us, without
disturbing the 0.5V DC signal that is forced on this node. I was
told this is possible with a combination of Tektronix TM502A (power
module mainframe), AM503B (current probe amplifier module with
digital scale readout), and an oscilloscope. I was wondering if
anyone here has experience with such measurements using this set
up, or may suggest a better method. From reading the AM503B manual
I get the impression that it does not have uA resolution, but then
I could have missed soemthing.

Many thanks.

Dan



Make/insert a small 10 turn wire loop to place the A6302 probe
around;that multiplies the current sensitivity by 10.
You may not disturb the signal enough to matter,it depends on your
circuit.

IIRC,the highest sensitivity of the AM503/A6302 is 1 ma/div.

Of course,you can also change the display scope's Volts/div setting
to magnify your resolution.(there are limits,though)
And AC couple the scope,or use one with an adjustable DC offset,like
a 7A13/7K combo.

IIRC,that's set at 50mv/div,50ohm inputZ.
AM503 system BW is 50 Mhz,IIRC.


BTW,I used to repair/calibrate AM503 systems at TEK-Orlando.
(before they shut all the field offices down)


Glad you said that.
I just got hold of an AM503 that had been severely "adjusted" to the
point its sensitivity was off by more than 25%.
Click to expand...
You have to watch for metal film gain resistors changing value.Then you end
up at the limits for gain pots,which may affect freq.comp.

I went through all the cal procedure, but got a bit confused by the
'adjust until getting good results' for the HF compensation resistors
and cap.

Do you have any good hint about this?
Click to expand...
Well,the AM503 amplifier can be "pre-adjusted" without the A6302 probe by
driving a signal into the connector,IIRC,there was instructions on how to
do this in the manual,and how to make the adapter.
One thing is that the A6302 probe is sensitive to being dropped and that
can crack the ferrite head or damage the Hall device and you'll never get
it to compensate properly.

also,some of those tiny adjustable caps can have the slot break loose from
the rotor disc and it looks tlike they're adjusting,but nothing
changes,because the disc itself is stuck and not turning with the metal
'slot'.They can also develop a black silver oxide underneath them and that
insulates the rotor from the metal stud,making it effectively open.

BTW,TEGAM bought the TM500 line from TEK,and were providing parts and
service for AM503. I'm not sure if this is still true though.
www.tegam.com

--
Jim Yanik
jyanik
at
kua.net
 
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