Products > Test Equipment
Picotest Injector Teardowns
tv84:
--- Quote from: Jay_Diddy_B on May 27, 2020, 06:17:21 pm ---I have marked the measured impedances on this drawing of the board assembly:
(Attachment Link)
to raise the impedance where the capacitor are, I need to widen the gap between the traces and the ground plane.
--- End quote ---
Damn! This is an optimization of my suggested change!!! :clap: :clap: Respect!
(I had removed it because, afterwards, I thought it was something irrelevant... )
sixtimesseven:
--- Quote from: 16bitanalogue on April 10, 2020, 12:05:00 am ---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
* 10kI 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.
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Another nice one would be the "2180A" preamplifier to up the sensitivity of 8bit scopes. I wonder how they have done it in such a small package.
corecode:
Could somebody explain what R1, R2, and C1 are being used for? R2/C1 look like some sort of high frequency roll-off, but at a surprisingly high frequency.
Thanks!
--- Quote from: Jay_Diddy_B on April 12, 2020, 10:58:48 am ---
LTspice model J2111A
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Wolfgang:
--- Quote from: corecode on October 13, 2020, 10:02:14 am ---Could somebody explain what R1, R2, and C1 are being used for? R2/C1 look like some sort of high frequency roll-off, but at a surprisingly high frequency.
Thanks!
--- Quote from: Jay_Diddy_B on April 12, 2020, 10:58:48 am ---
LTspice model J2111A
--- End quote ---
--- End quote ---
R1, R2 and C1 are needed to prevent HF oscillations. Its more or less an output damper.
Whats also interesting is that the circuit has a dead zone around 0V. Even if the current monitor output will be OK,
the sunk current is not. The manual did not show this until a few months ago.
https://electronicprojectsforfun.wordpress.com/measuring-a-picotest-j2111a-current-injector/
corecode:
Thanks for the quick answer.
I'm simulating a simplified circuit (no diodes, just sink from positive rail, different op amp (OPA358)) to understand the circuit and trade-offs. However, I get peaking without C2, and with C2 I get a roll-off starting around 1MHz. I guess I need to pick a different op amp?
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