Picotest Injector Teardowns

[16bitanalogue]

Hello All,

I am not sure if this is the best place to start a discussion about PicoTest Line Injectors. They are useful tools, but tend to be on the expensive side. I wanted to upload what I have to be archived, and for those who wish to design their own or at least are interested in such topics. I hope this helps someone, somewhere.

Picotest J2120A Line Injector
Price: $525
BOM:

(4) Capacitors

• C1||C2 = 35.7uF
• C3||C4 = 1.98uF

(1) Resistor

• 10k

(1) nMOS

• AOT2618 from Alpha and Omega Semiconductor, http://www.aosmd.com/res/data_sheets/AOT2618L.pdf

J2120A front and rear pics attached.

Picotest J2130A DC Bias Injector
Price: $525
BOM:

(24) Capacitors

• Parallel, Series network = 27uF

(1) Resistor

• 10k

I do believe the equivalent network of the 24 caps is 27uF, I may wish to double check when I get a chance.

J2130A front and rear pics attached.

Ridley Injector Isolator Transformer
No specifications really. The manufacturer looks to be Avel Lingberg.
Model CA8518.

I hope this comes out clean, first time poster. Hell of a time with the pics.

*EDIT*
Added front picture of the J2120A.

[Sighound36]

Hello 16Bitanalogue

This was going to be a couple of my next purchases much appreciated.

[Jay_Diddy_B]

16bitanalogue,

Thank you for the teardown pictures and welcome to the group.

Hello All,

I am not sure if this is the best place to start a discussion about PicoTest Line Injectors. They are useful tools, but tend to be on the expensive side. I wanted to upload what I have to be archived, and for those who wish to design their own or at least are interested in such topics. I hope this helps someone, somewhere.

Picotest J2120A Line Injector
Price: $525
BOM:

(4) Capacitors

• C1||C2 = 35.7uF
• C3||C4 = 1.98uF

(1) Resistor

• 10k

(1) nMOS

• AOT2618 from Alpha and Omega Semiconductor, http://www.aosmd.com/res/data_sheets/AOT2618L.pdf

J2120A front and rear pics attached.

Snip ...

I hope this comes out clean, first time poster. Hell of a time with the pics.

You seem to be missing the J2120A front picture, showing the AOT2618 MOSFET.

Do you have the J2111A Current Injector in your collection? I would like to see teardown pictures.

Thanks!!

Regards,

Jay_Diddy_B

[fcb]

Great first post.

The Ridley Injector unit (in blue) is still PatPending (and has been since at least 2010 - no sign of an actual granted patent), looks like it might have a second transformer (3E27 - which is MnZn core material) to handle the HF.

Whilst none of these boxes look like good-value, the BOM cost on the Ridley Injector ($600) unit is much higher than the Picotest ($525+) units.

Ridley videos on YT are pretty interesting.

[16bitanalogue]

You seem to be missing the J2120A front picture, showing the AOT2618 MOSFET.

Do you have the J2111A Current Injector in your collection? I would like to see teardown pictures.

I added the front picture of the J2120A to my first post.

I did manage to capture tear down information for the J2112A High Current Injector which is the big brother of the J2111A. I stashed the penciled schematic, BOM, and pictures somewhere. I will have to see where I squirreled them away, but if not I will have to capture them again.

I realize that most of these have a hell of a markup (engineering effort, mechanical design of the box, etc.), but it is certainly worth a DIY solution.

[Jay_Diddy_B]

Hi group,

Here is the J2120A schematic:




Regards,

Jay_Diddy_B

[16bitanalogue]

Picotest J2112A High Current Injector
Price: $1,995
BOM:
I will need to go back and measure the components. I lost that information. It is also difficult to see the part number on the SOIC8 - I want to recall it was an op-amp of some kind.

[Jay_Diddy_B]

Hi group,

For the J2130A the insertion loss is given as:




Working backwards from this the capacitance is 28.2uF with zero bias.

so 12x 4.7uF in parallel, 2 sets in series.


So we have:






Regards,

Jay_Diddy_B

[Jay_Diddy_B]

Picotest J2112A High Current Injector
Price: $1,995
BOM:
I will need to go back and measure the components. I lost that information. It is also difficult to see the part number on the SOIC8 - I want to recall it was an op-amp of some kind.

This looks like this:




This is basically a current sink that can work with either positive or negative inputs:

Regards,

Jay_Diddy_B

[Jay_Diddy_B]

Hi group,


**** Error - See this Message ****

https://www.eevblog.com/forum/testgear/picotest-injector-teardowns/msg3011600/#msg3011600


*****************************



Here is a working model that comes close to matching the specification that are published by PicoTest.

https://www.picotest.com/images/download/j2112a-spec-sheet-final-hires.pdf

LTspice Model




This is using one of the op-amps available in LTspice.

Simulation Results




I have attached the LTspice model.

Regards,
Jay_Diddy_B

[16bitanalogue]

I believe I can get a hold of a few more Picotest injectors.
I am hoping there is a J2110A floating around and the common mode transformer J2102B.

I'll try to keep this updated as they come.

[Sighound36]

Thanks for all your efforts chaps first class.

Howabout a group design and build?

[2N3055]

Fantastic topic!! Great work here!!

[Ribster]

I can design and assemble some boards if you guys are interested..

[Sighound36]

More than happy with that thank you

[Jay_Diddy_B]

Hi group,

Just playing around in KiCAD:



This software is new to me. I normally use something else.

100mm x 100mm board, no case.

Which injectors are the most useful?

Regards,
Jay_Diddy_B

[Sighound36]

Hi Jay_Diddy_B

Thank you for your efforts personally I would interested in all of them however the Picotest J2120A Line Injector would be a great place to start

[_Wim_]

I can design and assemble some boards if you guys are interested..

I am also interested in these! 

[Jay_Diddy_B]

Picotest J2112A High Current Injector
Price: $1,995
BOM:
I will need to go back and measure the components. I lost that information. It is also difficult to see the part number on the SOIC8 - I want to recall it was an op-amp of some kind.

The pictures that were included are actually the J2111A

I was having difficulty getting the component values, that I can read in the photograph, in the model agree with the datasheet performance.



This are the specifications:



LTspice model J2111A




And the modelling results:



I have attached the LTspice model.

Regards,
Jay_Diddy_B
 J2111A concept model.asc (5.46 kB - downloaded 119 times.)

[Jay_Diddy_B]

Hi Jay_Diddy_B

Thank you for your efforts personally I would interested in all of them however the Picotest J2120A Line Injector would be a great place to start

Hi,

I am a few hours into using KiCAD. This what I have come up with for the 2120A:



I am showing the IRF540, but the plan is to use the AOT2618.

The artwork is single-sided:






The board is 100mm x 100mm

The plan is to use Keystone 575-4 for the connections.

Comments?

Jay_Diddy_B

[16bitanalogue]

Picotest J2112A High Current Injector
Price: $1,995
BOM:
I will need to go back and measure the components. I lost that information. It is also difficult to see the part number on the SOIC8 - I want to recall it was an op-amp of some kind.

The pictures that were included are actually the J2111A

I was having difficulty getting the component values, that I can read in the photograph, in the model agree with the datasheet performance.

Oops! I couldn't remember which version since it has been several months. The performance is really close to the datasheet, so I would move forward with what you have. In the future, I can update with actual measured values and track down the op-amp that is being used. It may be moot, but I'll be happy to do it.

According to the User's Manual for the Signal Injectors, the J2111A is bi-directional; i.e., it can only SINK current up to 100mA with positive and negative voltages. Where as the J2112A can SINK up to 1A with positive voltages only.

[16bitanalogue]

The board is 100mm x 100mm

The plan is to use Keystone 575-4 for the connections.

Comments?

Jay_Diddy_B

I am personally partial to Keystone 7006 and 7007, but for low cost purposes the 575-4 are good.

2-layer, FR4, 1oz copper top pour.

[Wolfgang]

Picotest J2112A High Current Injector
Price: $1,995
BOM:
I will need to go back and measure the components. I lost that information. It is also difficult to see the part number on the SOIC8 - I want to recall it was an op-amp of some kind.

The pictures that were included are actually the J2111A

I was having difficulty getting the component values, that I can read in the photograph, in the model agree with the datasheet performance.

Oops! I couldn't remember which version since it has been several months. The performance is really close to the datasheet, so I would move forward with what you have. In the future, I can update with actual measured values and track down the op-amp that is being used. It may be moot, but I'll be happy to do it.

According to the User's Manual for the Signal Injectors, the J2111A is bi-directional; i.e., it can only SINK current up to 100mA with positive and negative voltages. Where as the J2112A can SINK up to 1A with positive voltages only.

When trying to build your own, watch for two pitfalls:

- The part has a dead zone at small voltages where the current drawn is completely incorrrect, even if the sense resistor says its OK.
- Have a look at the transistor datasheets. They will die if you draw max. current (dynamic plus offset) at 40V. If you want to keep
  this spec, you need better transistors and better cooling.

[Jay_Diddy_B]

When trying to build your own, watch for two pitfalls:

- The part has a dead zone at small voltages where the current drawn is completely incorrrect, even if the sense resistor says its OK.
- Have a look at the transistor datasheets. They will die if you draw max. current (dynamic plus offset) at 40V. If you want to keep
  this spec, you need better transistors and better cooling.

Wolfgang,

Thank you for the guidance. The cooling for the transistors is certainly inadequate for 3W of dissipation.


And yes there is a dead band where the devices doesn't work properly.



My interest in building these is to find out what they can do.


Regards,
Jay_Diddy_B

[Jay_Diddy_B]

Hi,

Further to my last reply, the manual that can be found here:

https://www.picotest.com/support.html

On page 44 it says the maximum input voltage is DC +  AC is 5V

5V x 74mA = 375mW

This is consistent with the transistor selection and mounting method.

Regards,
Jay_Diddy_B