HACKADAY PRIZE 2023: THIS DIFFERENTIAL SCOPE PROBE IS SMARTER THAN IT LOOKS
https://hackaday.com/2023/09/28/hackaday-prize-2023-this-differential-scope-probe-is-smarter-than-it-looks/?fbclid=IwAR39WOWdQdFvKcOQ0R8dXwK6qkgMCsBdHuH1lZ0nkFIs4vfBMW_cQPaDSRA

A differential probe, a device for measuring the voltage between two points in a circuit rather than the voltage between a point and ground, it an extremely useful addition to any electronics bench. Inside such a probe you’ll usually find a fancy op-amp working as a differential amplifier, and for correct operation they require careful adjustment to null out DC bias and achieve the maximum common mode rejection. We particularly like [Craig D]’s probe, because these adjustments are taken care of automatically by a microcontroller.

https://hackaday.io/project/191837-pd150

An active #differential #probe designed for the measurement and visualization of waveforms of mains voltage (or at mains’ voltage level) on a common #oscilloscope without running the risk of frying the scope, the probe, or worst yourself!

In a previous video (here: • Easy DIY passive … ) I’ve showcased a passive probe, unlike that one this active probe uses only one input channel of the oscilloscope.

The probe run on a 9V battery that lasts about 20 hours (based on Duracell’s data sheet calculated for the current drawn by the circuit.)
It features an input impedance greater than 4MΩ, an output impedance of ~50Ω and an attenuation ratio of x200 (200:1). The theoretical maximum input voltage is 800Vp (given by the voltage limit of the resistors used in the attenuator). This allows to take measurements not only on common 230/240Vrms but even at 380/400Vrms (used in Europe), including phase-to-phase on a three phases system.
BEWARE that if you try to make this project yourself you’ll do it under your own sole responsibility, I’ll take no liabilities! Keep in mind that the circuit’s performance and limits heavily depends by the components used and how the circuit has been made. I mounted two of the four resistors of the attenuator on the PCB and has been covered with an insulating resin that is NOT visible in the pictures.

The probe is built around an LM4562 in IA configuration, and a resistive attenuator. Tests confirmed that there is no need for capacitive compensation since the input capacitance is remarkably low (less than 2pF) and the frequency range of interest is about mains frequency (50/60Hz) and its harmonics, so rarely there is the need to read frequencies above 20Khz.
I hadn’t the possibility to test the probe for its actual bandwidth, though.

For the sake of simplicity I used common 1% resistors (with 20ppm/C) rated 250V. The “high” voltage must be well separated by the low voltage part. The key point of this probe is the link to ground, or PE (Protective Earth) that provides its safety. It works on both TT and TN systems. The PE is also carried by the oscilloscope, but the provision of a separate connection for grounding (the green banana socket) is important in the case of fault of the cable, the use of a battery powered oscilloscope and the case when the plug is disconnected from the scope.

This probe MUST NOT be used where the line is not protected by a GFCI, RCD or RCCB.

Easy DIY passive #probe to measure #mains with the #oscilloscope
https://www.youtube.com/watch?v=XGW_aqE4PVc

Do you have to measure mains voltage waveform just once in your whole life? Differential probes are too expensive? Here it is a simple, cheap, DIY solution.
CAUTION: Working on mains voltage is dangerous, you MUST know what you do.
Directly using the probes of the oscilloscope to measure the mains is hazardous, it could lead to from destroying your probes to melting the traces of the PCB inside your oscilloscope, not to mention the risk of being injured. Depending by the grid system you may have 50% to 100% chance of causing a short capable to destroy your instrumentation.
In an old video I presented a depth analysis of why you can blow up your oscilloscope while making measurements at mains, follow this link: • Correct use of th…
Also the trick that uses two probes directly may end up in catastrophic results if you work on voltages above 110V RMS.
In this video is presented a simple attenuator made of just 1/4W resistors, that guarantees safe operations with the oscilloscope provided the PE (Protective Earth, the yellow-green/green wire) is actually tied to ground. It still requires two input channels of your oscilloscope but it is safer than directly hooking the probes to the mains.

The new HVFO108, with 150 MHz of bandwidth, is suitable for both Silicon and Silicon Carbide designs. It is designed to measure small signals floating on an HV bus and delivers excellent performance, has high CMRR, and provides optical isolation to reduce DUT loading.

What is Common Mode Rejection Ratio (CMRR) and how to measure it on a high voltage differential probe or differential amplifier. Using the new Rohde & Schwarz MXO4 oscilloscope.

00:00 – What is CMRR?
01:53 – Why twist the wires?
03:26 – Typical CMRR figures
04:51 – How to measure CMRR – The Setup
08:54 – Remote R&S Oscilloscope desktop view & settings
11:22 – Output to input voltage ratio
11:58 – Beware of DC offset
13:36 – Does the 20MHz CMRR measaurement match?
14:02 – Input referred measurement
15:02 – Compensating for the gain
16:29 – Automated Frequency Response Analysis

https://www.eevblog.com/forum/blog/eevblog-1521-how-to-measure-differential-probe-cmrr/

Differential probes aren’t just for differential signals!

What is a differential probe? It’s a probe designed to measure a differential signal. But why are engineers everywhere using differential probes as general purpose measurement tools? Join Ally as she unveils this oscilloscope probing mystery.

Learn the three main values of a differential probe:
#1: Differential probes have a high common mode rejection ratio
#2 Probe loading is reduced with a differential probe
#3 Differential probes have higher bandwidth than single-ended probes

What is Common Mode Rejection Ratio (CMRR) and how to measure it on a high voltage differential probe or differential amplifier. Using the new Rohde & Schwarz MXO4 oscilloscope.

00:00 – What is CMRR?
01:53 – Why twist the wires?
03:26 – Typical CMRR figures
04:51 – How to measure CMRR – The Setup
08:54 – Remote R&S Oscilloscope desktop view & settings
11:22 – Output to input voltage ratio
11:58 – Beware of DC offset
13:36 – Does the 20MHz CMRR measaurement match?
14:02 – Input referred measurement
15:02 – Compensating for the gain
16:29 – Automated Frequency Response Analysis

https://www.eevblog.com/forum/blog/eevblog-1521-how-to-measure-differential-probe-cmrr/