Hantek CC-65 Current Clamp Probe – Part 3 – Signal Chain, Improving BW and Noise

This is the 3rd (and final) part of a series of posts on the Hantek CC-65 current clamp probe. In part 1 we went over the probe structure and circuit operation, and discussed possible issues and improvements. In part 2 we’ve started measurements and modifications of the probe, focusing on the power-supply (PS) and the sensor bias circuit. That allowed us to achieve lower noise on the supplies and sensor bias, as well as extend the circuit operation down to lower battery voltage.
In this post I’d like to go into modifications of the actual signal chain. This consists of the amplifier structure at the heart of the probe, but will also touch on the offset cancellation circuit. The main goal from my point of view is to both extend its bandwidth (BW) by at least an order of magnitude, and reduce the equivalent input noise density so that limited BW measurements can be made on lower amplitude signals.

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Hantek CC-65 Current Clamp Probe – Part 2 – Basic Measurements, Power-Supply Modifications

In the previous post we’ve gone over the CC-65 probe structure and schematic, and noted a few things that can be done to improve its performance. Other than modifying the probe with higher spec parts, there were a few design decisions and potential issues that were discussed. In this post I plan translate the previous discussion into actual measurements and modifications to the probe. I will cover only part of the circuit in this post, and will cover the rest in a follow up post. This time we’ll have a look at the power-supply and biasing circuit, while the actual amplifier/signal path will be covered in the next post.

I should start by saying that the parts shortage observed nowadays is affecting this project too, it is one of the reasons it took such a long time to get something done. In fact, even now, I’ve had to opt for some replacement parts which weren’t my preferred option, or else it would call for months of wait for parts to be back in stock. With that said, lets move on to some actual measurements.

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Hantek CC-65 Current Clamp Probe – Part 1 – Probe Analysis and Discussion

This post will discuss the Hantek CC-65 current clamp probe, a cheap and useful tool. I’ve ordered this probe because of its low cost, and reasonable performance. I was happy to see there’s even a schematic for it available online as drawn in a post on the EEVblog forum. Looking at the schematic made it clear there’s a lot that can be done to improve it fairly easily. Due to the length of the post, and the fact I’m still waiting for the parts to arrive, I’m going to split this post into a few parts. In this part we’ll go over the operation of the probe and its schematic, and then discuss possible modification that can be made to it. There are quite a few tradeoffs to be made in the selection of parts and which mods to do, based on the requirements out of the probe. I will detail some of these considerations, and in the next parts will present results based on the mods I’ve decided to implement according to my preferences.
This part turned out to be quite long with a lot of text and little pictures/results. I think this is of value and will serve as good background and reference in the next parts on this topic where measurement data will be presented. There, it will be possible to simply point to the relevant part of the current post, to explain the reasoning behind chosen components for mods, and measurement results explanations.

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Control Program for BK Precision 8500 DC Electronic Load

This post will be somewhat different to others, but I consider it interesting enough and useful enough to share on the blog. Over the past years I have used MATLAB quite a lot for communicating with instrumentation/test boards I’ve designed. Due to a number of reasons I’ve recently decided that gradually transitioning to use of Python instead is a good idea. My needs are typically quite basic, some communication with external instrumentation/test boards, data recording, data analysis, and finally generating some nice looking figures to summarize the results. Since the best way to learn is do, I’ve decided writing a control software for a DC electronic load I own would be a nice first project. The code is finally complete, so I’ve decided to share it with others so that anyone who owns an instrument from this series could use it.

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Agilent 54831B Oscilloscope Taming

Just like any other DIY electronics hobbyist, a scope is one tool I can’t live without. Over the past few years I’ve owned the renowned Rigol DS1052E (which was hacked up to the 100MHz model), and more recently a Siglent SDS1204X-E. Both were great for the price and their respective time to market. The DS1052E was probably among the first scopes that almost every hobbyist could afford, and the SDS1204X-E was much more capable with more channels and processing power and its MSO option (which at the time was quite buggy, but I understand it has improved). However, the thing I was missing is the ability to probe (relatively) high speed signals. I wanted something that could do 500MHz, and preferably even 1GHz. Getting such a high BW scope would cost quite a lot of money brand new, so I knew I had to look for some older used units. After reading a bit on different forums, I’ve decided that an Agilent 54831B would be a good match for my needs. In this post I’d like to describe some mods I did to the scope to make it better suited for my needs. Hopefully some other readers will find this useful to learn about this scope, or how to mod it if the need arise.

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