¿ªÔÆÌåÓý

ctrl + shift + ? for shortcuts
© 2025 Groups.io
  1. TekScopes
  2. Topics

TIP: Current Probes ...

 

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
stefan_trethan
 

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).

ST

On Sun, Dec 9, 2018 at 6:30 PM David Slipper <softfoot@...> wrote:


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
 

Mine has a bandwidth of 20KHz (probably 1/2 that is usable) which is
more than adequate for my needs.

The only problem with it is the zero drifts, but I can live with that.

Dave
Bob Albert
 

I checked on ebay and the cheapest adapter I could find was almost $20; not very sensitive (1 mV per Ampere) and no idea of bandwidth.
If anyone knows of a project to create a current probe I would be interested.
Bob

On Sunday, December 9, 2018, 11:06:03 AM PST, David Slipper <softfoot@...> wrote:

Mine has a bandwidth of 20KHz (probably 1/2 that is usable) which is
more than adequate for my needs.

The only problem with it is the zero drifts, but I can live with that.

Dave
 

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).
stefan_trethan
 

The LEM sensors come complete with core, and I believe some even split open.
The Allegro sensors are just ICs that sit over a PCB trace without
magnetic circuit, I don't believe they are as good for what we want to
do.

------------------------------

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).
stefan_trethan
 

To answer my own question:


But only 47kHz, I'd like something like that with a couple hundred kHz....

ST

On Sun, Dec 9, 2018 at 8:38 PM stefan_trethan <stefan_trethan@...> wrote:

------------------------------

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).
Craig Sawyers
 

Design a Rogowsky coil. With the right design you can go from about 200Hz to 5MHz. Needs a wideband
active integrator since a Rogowsky output is proportional to dI/di.

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of stefan_trethan
Sent: 09 December 2018 19:52
To: [email protected]
Subject: Re: [TekScopes] TIP: Current Probes ...

To answer my own question:


But only 47kHz, I'd like something like that with a couple hundred kHz....

ST

On Sun, Dec 9, 2018 at 8:38 PM stefan_trethan <stefan_trethan@...> wrote:

------------------------------

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).
 

Hey Craig- try 'Rogowski'............ I have used them extensively, BTW

DaveB NZ-( the pedant!!)

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Craig
Sawyers
Sent: Monday, December 10, 2018 13:32
To: [email protected]
Subject: Re: [TekScopes] TIP: Current Probes ...

Design a Rogowsky coil. With the right design you can go from about 200Hz to
5MHz. Needs a wideband active integrator since a Rogowsky output is
proportional to dI/di.

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of
stefan_trethan
Sent: 09 December 2018 19:52
To: [email protected]
Subject: Re: [TekScopes] TIP: Current Probes ...

To answer my own question:


But only 47kHz, I'd like something like that with a couple hundred kHz....

ST

On Sun, Dec 9, 2018 at 8:38 PM stefan_trethan <stefan_trethan@...>
wrote:

------------------------------

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).
 

Re current clamps - It does not seem to be generally known that the stock
standard Fluke 80i-600 when used with a 100 ohm burden- is flat out to
around 50 kHz or more. No doubt some other std current clamps will give
similar results but I've not bothered to check.
DaveB, NZ
stefan_trethan
 

I know more about Rogowski coils than I am comfortable with, having
designed one that will work down to well below 0.1Hz over the last
couple years, but only under certain conditions which I can't discuss.

But I'm looking for a spot or (small area) sensor now. Something I can
use like a voltage probe on the surface of a PCB for example.
It should go down to real DC. Maybe a dual path solution is called
for, similar to the standard current probes with a pickup coil and
that TI sensor.
Just open circuit without the ferrite core, maybe without compensation even.
Or maybe I'll just buy a damn iporober 520 one day... I just hated
their marketing wank back when it came out.

ST
On Mon, Dec 10, 2018 at 1:32 AM Craig Sawyers
<c.sawyers@...> wrote:

Design a Rogowsky coil. With the right design you can go from about 200Hz to 5MHz. Needs a wideband
active integrator since a Rogowsky output is proportional to dI/di.

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of stefan_trethan
Sent: 09 December 2018 19:52
To: [email protected]
Subject: Re: [TekScopes] TIP: Current Probes ...

To answer my own question:


But only 47kHz, I'd like something like that with a couple hundred kHz....

ST

On Sun, Dec 9, 2018 at 8:38 PM stefan_trethan <stefan_trethan@...> wrote:

------------------------------

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).

1 - 11 of 11