Products > Test Equipment

PRP1 - Low cost 2GHz power rail probe

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Kean:
I received my PRP1 today.  It will be a few days at least before I can spend time with it, but it looks great.

A few pics are attached in case anyone is curious, but I have not taken it apart... yet...

tszaboo:
Hi, some update. I've sent the first few PRP1s to people who ordered it. I have just 3 of the batch left.
If I decide to do another batch that's likely to only happen in 2025, and probably going to be a group buy, so it could be a while.

scottapotamas:
Mine arrived the other day and I had a quick moment to get familiar with it today by doing some quick measurements.

In short, does what I expected so far and matches the described specifications well enough. I'm looking forward to using it seriously, and happy to add it to the toolbox.
Overall a solid first-batch of a hobby(?) project. Throughout the process (questions prior to purchase, ordering/shipping) tszaboo was helpful and responsive!

I'll come back after I've used it enough with real projects to actually provide valid feedback.


Tried to match test setup against tszaboo's published setups as per GitHub doc
Screenshots attached are named accordingly.

DC Resistance - 49.9829 kΩ when zeroed, 4-wire measurement on 2701.
Power consumption - 5.004 V from DP832. 13.201116 mA measured with 2701 (filtered, 5 PLC)


* All tests were done with a lab PSU providing 5V rather than scope USB.
* My scope doesn't support 1.2 input attenuation. Both channels are left at 1x, 50 Ω internal, no BW limit unless mentioned.
* The PRP1 is always on CH1.
* Used my own BNC and SMA cables, adapters etc. All first owner+name RF brands etc, all overkill for >6 GHz work.
* I noticed during the gain test that my sig-gen (DG1022) wasn't too great at hitting the Vpp setpoints. The output BNC was into a tee then connected to the PRP1 and CH2 as reference. I'd expect relative comparisons to be OK.
* I'll try to setup the RSA to look at spectral performance and attempt crude replications of the VNA measurements

There are some screenshots of a quick real-world setup looking at the output of a 12 V buck-boost reg built on the TI TPS552892.
It's running in step-down PWM mode with a 2 A load, and I've intentionally removed the snubbers on the switching nodes.


* The SMA pigtail included with the PRP1 kit is connected (poorly) to PTH testpoints on the output.
* A 10 MΩ passive probe (CH2) using the default ground antenna/clip is poking at the same output test-point.
Because the rail is around 12 VDC, CH2 hits the 10 V vertical offset limit and can't be used with DC coupling and a sensitive scale at the same time.
The coarse+fine offset of the PRP1 handles this as expected, while showing a better representation of the signal.

The screenshot can't show it, but the blue CH2 trace can be influenced by handling the probe cable. Becoming a human radiator/capacitor by holding a finger to some parts of the board picks up a lot of unwanted noise. The PRP1 waveform is unchanged and robust.

tszaboo:

--- Quote from: scottapotamas on December 04, 2024, 12:07:20 pm ---Mine arrived the other day and I had a quick moment to get familiar with it today by doing some quick measurements.

--- End quote ---
Many thanks for the detailed write up, I'm glad you find it useful.
I use "Custom" attenuation on the oscilloscopes that I tested the unit on. If that's not supported, than a Math channel could be used for the probe attenuation. I think on some scopes you might even add the DC offset in with the Ax+B computation, and get the correct values on the screen.


--- Quote from: scottapotamas on December 04, 2024, 12:07:20 pm ---I noticed during the gain test that my sig-gen (DG1022) wasn't too great at hitting the Vpp setpoints. The output BNC was into a tee then connected to the PRP1 and CH2 as reference. I'd expect relative

--- End quote ---
Signal generators expect 50 Ohm load on their output. The PRP1 load is never really 50 Ohm, it's somewhere between 60-50KOhm depending on the frequency, by design (that's the whole point of it). I had a bit of trouble making the test setup first, until I realized I would need a source with 0 Ohm output, or do a relative measurement.

scottapotamas:

--- Quote from: tszaboo on December 04, 2024, 12:48:33 pm ---I use "Custom" attenuation on the oscilloscopes that I tested the unit on. If that's not supported, than a Math channel could be used for the probe attenuation. I think on some scopes you might even add the DC offset in with the Ax+B computation, and get the correct values on the screen.

--- End quote ---

I don't believe I have a custom attenuation setting unfortunately, though I should try abusing probe compensation settings.
Ax+B isn't a great on this scope and most of my troubleshooting or tuning can tolerate relative measurements most of the time.


--- Quote from: tszaboo on December 04, 2024, 12:48:33 pm ---Signal generators expect 50 Ohm load on their output. The PRP1 load is never really 50 Ohm, it's somewhere between 60-50KOhm depending on the frequency, by design (that's the whole point of it).

--- End quote ---

Yeah. I had the sig-gen set to 50R output to drive the scope's 50R, and basically just let the PRP1 hang off the tee. It should only be a few milliohms off so I didn't expect >5% error on the scope Vpp.
Saying that, 8-bit scopes aren't great tools for precision voltage measurements and the arb probably needs a closer look because it's spent a few years acting as a glorified TTL/LVCMOS pulse generator.

[EDIT]: Just checked the DG1022Z's 50R output spec and it's ±(1% of the setting value + 5mV + 0.5% of the amplitude) which explains it. Sorry for the off-topic clutter.

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