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PRP1 - Low cost 2GHz power rail probe

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temperance:

--- Quote --- They were creating strange low frequency drift. I have to assume, that pushing the plastic housing of the trimpot introduces stress that will upset uV level signals.
--- End quote ---

Interesting observation. But probably hard to avoid as the contacts must settle after tweaking. But some ten turn pot's are better than others.

One of the better pot's around:
https://www.bourns.com/products/potentiometers/industrial-panel-controls/product/3310
https://www.bourns.com/products/potentiometers/industrial-panel-controls/product/91-95

Those are used in pro audio equipment where those pot's are exposed to extreme vibration. (like next to stack of subs.)

But of course that doesn't say anything about the effect you've noticed.

I have some of those laying around (10K linear). Now I'm curious...

temperance:
Data for the 9195 attached.

That's a 5K pot.

 DMM-5 Run 4 2020-08-06T15.00.35.xlsx (440.12 kB - downloaded 25 times.)

temperance:
I had an other fancy pot in my collection. Brand new.

Vishay PRV6

Edit: the remainder are some low cost pot's not worth testing.

Neganur:
👍 nice

hpw:

--- Quote from: tszaboo on August 23, 2024, 10:00:25 am ---I'm calling this PRP1. It's a power rail probe, that is oscilloscope agnostic and low cost.
I've started working on this because normal power rail probes cost around 10 times as much as entry level oscilloscopes. I hope to change that with this probe.

Specifications:
Max voltage offset: ±24V
DC Input impedance: 50kΩ
High frequency input impedance:b50 Ohm
Signal attenuation of 1.2:1
Transfer function within 1dB to 2GHz
Estimated noise: 42 µVp-p to 20MHz
Active signal range +/-500mv
Course - Fine adjustment
USB Type C 5V power input - run it from your oscilloscope directly
SMA input and output. SMA to BNC cable to connect to oscilloscope
Typical power consumption of 20mA


--- End quote ---

I did some early experiments as using an LNA (about 20dB gain) with 2 * +/- 9V  batteries to measure the power ripple on various digital ADC/DAC. Differential, as to use similar PIN header connections as LeCroy AP034 differential probe.

It started wit the differential AD8129 OPAMP with capacitors coupled and alike Pin header connections, this means no DC support but with higher load.

While on ADC/DAC VRef is a critical on low PN frequencies as low as 10mHz. In addition the ripple on ADC/DAC digital or analog part. The ripple tells you much what is on the chip going on (or not should be drawing in any case).
The GND current with unknown current on DUT & LNA & DSO must be avoided.

The critical goes than on high RF frequencies as the CMRR of the LNA amplifier will go down the hill.
Only MISIC show nice CMRR but never checked how they really performs. The 1GHz as for -3dB down really about 600MHz.

At the end it shows about 3 different LNA devices required as:

- 0.0xx mHz to 100Hz (large input capacitors required)
- 10Hz to view xxMHz as for the average use
- xxxHz to RF a 1GHz with good CMRR required as the beef test with high ADC/DAC with 100MHz locks.

Important to check with asymmetric connections on a DSO with good ADC resolutions as SDS2000 Plus 10Bits and input probe scaling for the LNA.

The FFT size & FFT Window is by this DSO not optimal for all ranges (SDS7000 as with 32M samples at best).

Later on a nice rtHz plot is an must do as BIN export and import with an FFT Analyzer.

Some parallel entries found on diyaudio Equipment forum :D






 

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