Hacking Keysight Autoprobes

Puzzle: What is wrong with the following picture ?


Keysight offers an awful lot of AutoProbe enabled oscilloscope probes for their better scopes. These probes have a mechanism that will automatically detect the probe, set the scaling factor and other parameters, memory calibration parameters and other niceties.

But, what if Keysight does not happen to have a probe for your special requirements ? Then, so far, you are out of luck because Keysight is not willing to disclose their probe interface.

In my case, I needed a robust but very low capacitance FET probe (1:10, 1pF 1MegOhm, +/-20V linear range, 100V destruction limit). Frequency range was only about 100MHz, so no issue. Such a probe is not offered by Keysight. So, if you want automatic recognition and the other goodies, we are in for some reverse engineering go get it done. The modest result is shown below:


This part behaves and is recognized as a 1GHz Keysight 1:10 FET probe. An SMA connector has the probe signal, and the microphone connector supplies probe power and offset.

Update: I added the Keysight N2818A 200MHz differential probe to my team. Works great !

Details can be seen at:

Hacking Keysight Autoprobe EEPROMs

An Autorange Cap ESR Meter with SCPI Connectivity

OldElectrolyticsPictureNeed a cheap but accurate cap ESR meter that can be calibrated and has SCPI connectivity for calibration and readout? Of course you may buy some meter from hung low to renowned suppliers, you could employ a bridge or splurge on an impedance measurement instrument. All too much effort? Then this little instrument is for you. It has

  • 20mΩ to 50Ω measurement range with no range switching necessary
  • 100kHz measurement frequency
  • 5% precision over the complete range
  • SCPI controllable
  • Calibrated with 1% resistors for the complete range
  • works as an Arduino UNO/LEONARDO Shield


Click here for more details

A Small RF Power Meter with SCPI Connectivity


Need a small RF power meter with remote control capabilities ? Of course, you can buy this from the big names (Keysight, R&S, Anritsu, …). You get multi-sensor capabilities, wide dynamic ranges, a lot of measurement modes, fast reply, … but for a flexible solution about 10K€ are gone, and a simple commercial USB sensor is more than 3K€.

If you just need a frequency range up to 100MHz and you can live with a -65dBm to +5dBm range (attenuators can be accomodated) there is a cheaper solution that works fine:

A Small RF Power Meter with SCPI Connectivity

It uses an Arduino and an AD8307 to do the trick, and it works fine. Total cost is less than 100€, not too bad for an accuracy of 1dB. Its all USB powered and can be used by standard SCPI tools and libraries (uses NI VISA).

An Automatic Calibrator for Rigol DP832(A) Power Supplies

Do you have some Rigol DP832(A)s that are a bit overdue for their yearly calibration, but you dont want to send them in (>100€ + VAT + Shipping) or want to do a manual calibration (1h minimum) ? Then there is a smarter solution:

A SCPI-controlled calibrator that will coordinate all measurements automatically. Attach your DP832, a Keysight 34461 or better DMM, start a script – and wait ca. 10 minutes.


Done. See the link below for details:

An Automatic Calibrator for Rigol DP832(A) Power Supplies


A Generic Screen Capture Tool for SCPI Instruments


SCPI is like a haunting dinosaur lurking in all kinds of better and top-notch lab instruments. Unfortunately, the dinosaurs of different manufacturers all work differently if you as them to do a hardcopy and transfer it to your PC.

After fruitless attemps to do this with manufacturer software, I wrote my own little tool in Python that does the ugly work for some instruments from Keysight, R&S, Rigol and Tek. Click below to see the details:

A Generic Screen Capture Tool for SCPI Instruments

A sample screen is shown here:


and the good thing is that it can also do screenshots from instruments without a screen and/or missing SCPI hardcopy commands !

Homebrew SCPI Instruments



Are you living in a SCPI-infested lab world where a lot of standard equipment is used to be remote-controlled by SCPI, and now you want to automate an instrument that you have made, in exactly the same way, preferrable by some high-level language like Python or the like ?

Then its time to create some SCPI-controllable parts of your own. Here we are:

Click here to see how to Homebrew SCPI Controllable Instruments with Arduino Controllers

Power Supply Impedance Measurements Using an AP300 Frequency Response Analyzer

After testing a Keysight E5061B-3L5 and an Omicron Bode100 VNA, I got another LF frequency response analyzer (not a full VNA) on loan, the AP Instruments AP300. This unit has a low frequency limit of 10mHz, way lower than the other instruments. It looks like this:


I use these units to determine the output impedance of linear, low noise power supplies.

Click here for a Power Supply Impedance Measurements Using an AP300 Frequency Response Analyzer …

Phase Noise Measurements of Homemade and Commercial Oscillators and Signal Sources

Having an FSUP Phase Noise Analyzer on loan for an oscillator project (thanks N1UL !) I had the chance to check the phase noise of some commercial and homebrew oscillators and signal sources.


PhaseNoise10MHzRubidiumStandardLPRO1Hz1MHzFSUPThis a an EFRATOM LPRO101 Rubidium Standard. I also measured a commercial MillRen OCXO, a GPS standard, a Keysight N5171B RF signal generator and a RIGOL DG1062Z.

Click here to see some Phase Noise Measurements of Commercial and Homemade Oscillators …

Silly Circuits -Unusual Behaviour of Crystal Oscillators

Normally, crystal oscillators are standard components, used thousands of times without too much engineering attention necessary. If it comes to high quality crystals, a lot of unexpected effects can occur, like generating several nonharmonic frequencies at the same time and even chaotic behaviour.

here in the time domain:

Click here to see some Unusual Behaviour of Crystal Oscillators …