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Are there any cheap approximations of the Iprober 520 fluxgate sensor
current probe?
Maybe some sort of IC?

ST

On Sun, Dec 9, 2018 at 8:19 PM David Slipper <softfoot@...> wrote:

I did look at making one with a Hall sensor - the electronics isn't a
problem but the difficulty arises (for me at least) in cutting the slot
in a ferrite ring to put the sensor in or even splitting the core to
make a clamp. I guess it's easier if you have access to the right tools.

Any ways, this works well for me :-)

On 09/12/2018 18:52, stefan_trethan wrote:

If you only need low frequency the LEM brand hall effect sensors, I
believe Allegro also makes chip based ones, can be an option.
Also remember you can put 10 turns through if you need more
sensitivity (insertion impedance permitting).

I did look at making one with a Hall sensor - the electronics isn't a
problem but the difficulty arises (for me at least) in cutting the slot
in a ferrite ring to put the sensor in or even splitting the core to
make a clamp. I guess it's easier if you have access to the right tools.

Any ways, this works well for me :-)

On 09/12/2018 18:52, stefan_trethan wrote:

If you only need low frequency the LEM brand hall effect sensors, I
believe Allegro also makes chip based ones, can be an option.
Also remember you can put 10 turns through if you need more
sensitivity (insertion impedance permitting).

If you only need low frequency the LEM brand hall effect sensors, I
believe Allegro also makes chip based ones, can be an option.
Also remember you can put 10 turns through if you need more
sensitivity (insertion impedance permitting).

I quite often have a need to sense small currents (~10-200mA) and have
always wanted a clamp on current probe but even the used ones for a
scope are out of my budget.

A series resister is one solution but it is rather intrusive and
sometimes the circuit cannot tolerate the voltage drop.

Recently, at a garage sale I came across an old RS current clamp
intended to be used with a multimeter, it is a Hall effect device so
it's good for DC too, so just as an experiment I attached it to my scope
with a "banana<--->BNC" adapter and it works a treat :-)

The sensitivity is 1mV for 10mA and the bandwidth seems adequate for my
needs. If I need better sensitivity I just wind the wire 10 times around
the sensor clamp which gets me 1mV per 1mA.

Since I'm trying to get an Arduino and ESP8266 WiFi adapter to run on
batteries it is proving invaluable.

It may not have the bandwidth of a purpose built 'scope current probe
but it seems OK for my needs.

Dave

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Roger Evans via Groups.Io
Sent: 09 December 2018 08:27
To: [email protected]
Subject: Re: [TekScopes] 466 Channel 2 problem

Colin,

If you press the beam finder and then switch Ch 2 to 'invert' does the position of the channel 2 trace move? This is a quick check on whether the channel 2 imbalance is before or after the >invert circuitry (Q220 - Q226).

I am puzzled when you say that you 'mostly cannot see anything untoward' on channel 2 voltages and then say that the voltages on TP11 and TP14 are very different. Are they the only >places where the DC voltages on the two halves of the paraphase amplifier are noticeably out of balance? Since the amplifier is DC coupled throughout a failed transistor or diode tends to >upset the DC levels through other parts of the chain and finding the failed component can take patience. If the transistors are socketed then just pulling them out for testing, or swapping >with the corresponding channel 1 parts if you don't have a transistor tester is an easy route. If they are soldered in then you need to measure Vbe and Vce to check that they are consistent >with a transistor operating in its linear regime. Don't forget that the switching diodes CR314 - CR318 are part of the DC circuitry so a failed diode will also upset the amplifier balance.

The probablility is that you have a failed semiconductor but it is possible that a resistor has drifted badly over time.

Roger

Consider the time scale on Leo's plots and the response of the scope he's using which is what you are seeing in the calibration plot. I can't find my plot right now as my bench is undergoing at upgrade and everything is a huge mess. But IIRC the entire length of the step response Leo provides is less than the sample rate of anything most of us are likely to own.

I have put the BNC version on a new MSOX3104T. 436 pS rise time and 7% overshoot. I discussed with Keysight support which confirmed what I was seeing. A 750 MHz low pass filter reduced the overshoot to well less than 1%. But I could not inline the filter.

I then had an RTM3104 on demo. It arrived with 350 pS rise time and 3% overshoot. If I applied a 1 GHz LPF I had no visible overshoot. I was ecstatic. But for some legal reason the K18 option is not available in North America and the available FFT was completely useless. It was suggested that I install the 1.300 FW update. After that it had 10% overshoot. Restoring 1.100 did not restore the original response.

I've looked at 4 other scopes with Leo's pulser. I have no doubt that the waveform I saw is the true step response of the instrument. Now if you have one of the new Keysight 256 GSa/S 111 GHz DSOs, you probably need a better signal source. I suspect it would require one to give an accurate picture of the step response of Leo's pulser.

There are a large number of plots of the pulser output made on a wide variety of scopes in this thread.



My big problem at the moment is he's developed a version that produces 100pS wide pulses. I'm trying to come up with a justification for buying one.

I was amused that there were two posts in succession about Leo's pulser.

I think that in many
cases if you removed the plastic you would find the handle
was thin and spindly with sharp edges

That can be confused with a type of guitar pickup. :)


Michael A. Terrell

The other common term (at least on my side of the pond) was hum bucker.

Craig

On 12/8/18 6:36 PM, toby@... wrote:

The "wife seeks to get rid of 97 of husband's instruments by Sunday,
local pickup only", that we see semi-regularly now, is far from the
worst case scenario.

WCS = surviving wife driving tractor over instruments?

WCS = Son calling the "got junk?" company?

WCS = survivors putting craigslist ad for $500 per instrument, and one sells, rest go to estate sale buyer for $75.

WCS = daughter delegates to her daughter, who calls local donations nonprofit that is expert at appraising silverware and furniture and clothing.? Instruments go to Salvation Army and are forwarded to e-waste company.

etc, etc...

From: Brad Thompson <brad.thompson@...>
Sent: Dec 8, 2018 10:58 PM
To: [email protected]
Subject: Re: [TekScopes] wrenching ( was: Capacitor sniffing) OT

On 12/8/2018 10:42 PM, Chuck Harris wrote:

If by stink, you mean smell, a lot of plastics start out
benign, and end up really smelly. I have a set of Craftsman
nutdrivers from the 1970's that woke up one day and smelled
like vomit. And, have ever since.

I don't know if it is something the acrylic handles were
exposed to, or perhaps a plasticizer that was put in them
to make them less brittle, but I do know it stinks.

Hello, Chuck--

I have a set of those, too. A set of screwdrivers from that time
don't smell like much of anything.

From: Chuck Harris <cfharris@...>
Sent: Dec 8, 2018 10:42 PM
To: [email protected]
Subject: Re: [TekScopes] wrenching ( was: Capacitor sniffing) OT

If by stink, you mean smell, a lot of plastics start out
benign, and end up really smelly. I have a set of Craftsman
nutdrivers from the 1970's that woke up one day and smelled
like vomit. And, have ever since.

I don't know if it is something the acrylic handles were
exposed to, or perhaps a plasticizer that was put in them
to make them less brittle, but I do know it stinks.

As to plastic dipped wrench handles. I think that in many
cases if you removed the plastic you would find the handle
was thin and spindly with sharp edges.... The plastic is
there to hide manufacturing economies.

-Chuck Harris

From: Jim Ford <james.ford@...>
Sent: Dec 9, 2018 12:56 AM
To: [email protected]
Subject: Re: [TekScopes] wrenching ( was: Capacitor sniffing) OT

Yeah, I had a friend in high school who used to buy cheap tools at the swap meet.? The infamous "lead-head" hammer that got dents in it after pounding in nails and the ratchet extender that twisted at the ratchet end but didn't move at the socket end come to mind.? ?I kept telling him that he was going to get hurt using crappy tools.? Not sure whatever happened to that guy...? Poor quality tools are not only false economy, they can be dangerous.
Jim F