(NB All this is based on personal recollections and dates must not be relied upon too much. It’s all opinion and my experiences - if you need facts then check them !)
By now you may have realised that a little mix-up has resulted in the testers for this Road test being sent the wrong scope. Replacements are on the way so normal service will be resumed soon but having primed oneself for starting a road test it’s hard to back down.
colporteur has posted a blog with his first impressions of the included Probe Positioning Kit so obviously that won’t do for me.
I’ve been impressed by Gough Lui’s Road tests where he places the items into their competitive position in the marketplace – and I’ll have a stab at that later. But for now, in the absence of the actual scope, I’ll try put it in its place in history. Since it’s new it has no history of its own, so I’ll write about my history with scopes – leading up to the 6424E. It might be interesting, and it will give members a feeling for my approach and credentials.
Thinking about this plan I found it a little sad that so many of the companies who made my scopes are no longer in business or no longer making scopes.
My First Scope
My first scope was a cast off from Elliot Automation (where my Father worked) and was a Cossor 1049.
There is one for sale on Ebay, right now – it’s a splendid beast.
Not only is it a CRT scope but a true twin beam one - two electron guns in the tube, none of that ghastly chopping or alternate channel stuff ! It’s all valve (of course) and is alleged to contain not one single electrolytic capacitor – although it does use the good old paper and wax jobs !
I recall the bandwidth was 1MHz but some sources say 100kHz. I won’t argue the point – I was only about 12 when I got it. I remember I couldn’t move it easily – it weighs 35kg ! That shade around the screen is solid cast metal.
Cossor were a great company, long gone now. They made all the valves and the CRT themselves.
Interestingly this is the only scope that I have ever owned personally, all the subsequent ones have either belong to my employer or my own business.
Early Work Scopes
I can vaguely remember a couple of Telequipment CRT scopes that I used while working at Lustraphone (who made microphones and eventually (but briefly) Hifi). These were purely analogue days and scoping did not figure anything like as much as it does now.
Around 1976 I was working at Lamerholm Ltd (a business set up by my Father and me) and it was then that we bought a Scopex 4D10 or 4D25 (can’t remember which).
Scopex were based in Letchworth a few miles away from us. It was a simple and basic two channel scope – I seem to remember that it wasn’t that good.
Our business grew and took over another company, I don’t remember any more scope buying until 1983, when we bought two Gould OS300 scopes. I know this because I still have one of them. I rescued it from a skip. It lives under the bench now so I got it out and brushed the dust off it – it’s still working but seems to have developed a mains hum problem. We used to like the Goulds, they were the best analogue scopes we had and very quiet. I was able to download the service manual for it so perhaps I can fix it.
I vaguely recall a Tektronix analogue scope which I very rarely used (and didn’t like) – I don’t remember the model number.
Early Digital Stuff
The business had moved into making test equipment based on micros (initially Motorola 6802, 6805, and 6809). At the time there were analogue storage scopes at fabulous prices which could store an image of a single event so you could study it.
Digital scopes were beginning to appear but were absurdly pricey – we bought a Thurlby DSA524 (Digital Storage Adapter). This was a digital scope but without a display, for which purpose it used a standard CRT scope. (No cheap PCs and laptops, the IBM PC was launched in 1981).
I seem to recall the DSA524 was about £500 at the time – it worked amazingly well and was much cheaper than alternatives. There is quite a lot about the 524 on the web, and they come up on Ebay quite frequently – I don’t think I would like them so much now.
Eventually we bought our first real digital scope, an HP54622D – this was my first real digital scope – it still had a CRT but it was a raster scan tiny TV type. It also had a built in 16 channel logic analyser. We did some good stuff with that, including a pretty nifty MC6809 based hybrid digital and analogue Tester for BT (167C) and our first FPGA based design (which used 6 FPGAs from Xilinx in the days when the biggest part they made had 100 LUTs).
All good things pass and the DotComm bubble wiped out that company – I saw it coming and left a little before the bitter end and set up my own design business.
Digital ERA Scopes
Once I was working on my own about the first thing I did was buy my own HP54622D – only it says Agilent on the front. I still have it – and here it is.
The digital capabilities are a bit limited, but its analogue sections are pretty good (Good analogue is a feature of HP/Agilent/Keysight scopes).
I bought a couple of cheap logic analysers and around 2010 I bought a LeCroy WaveRunner 44Mxi. I got a very good end of line deal from Farnell (couldn’t have afforded it otherwise). This was a very good 4 channel scope but had no logic ports – like most LeCroys it has very good analogue sections and samples fast enough to make the headline bandwidth useable. It’s a 400MHz scope sampling at 5G/s (and by 5G/s LeCroy mean on all 4 channels, if you only want 2 it can do 10G/s). It has a built in PC and was very nice to use.
You’ll notice that I speak of it in the past tense – it doesn’t work any more and LeCroy won’t supply spare parts or a service manual.
But I didn’t know that in 2014 when I bought a LeCroy WaverRunner 610Zi with an 18 channel digital pod. It was/is a very nice scope. I needed 1GHz and it samples at 10G/s (all 4 channels, 20G/s if you only use 2). The triggering and digital stuff was good – it came with basic protocol decoders but it’s very expensive to buy extras.
It has a PSU fault now (it lasted 6 years) and once again LeCroy offer only a take it or leave it send it back to them for repair policy. It can be coaxed into working (usually) but of course can’t be relied upon. It’s a shame because it probably needs a replacement part costing under £10 but they won’t supply service information. Roll on the “Right to Repair” movement.
Since the LeCroy can’t quite be counted on, and certainly can’t go out on trips – I needed a new 1GHz scope. I looked around a lot and was able to get a very good offer on a Rhode and Schwarz RTA4004 (supplied fully loaded with all options) at about 50% of previous list price.
It’s quite a nice scope, nothing like as intuitive as the LeCroys and the screen is too small for all the things it tries to do. I use it connected to a PC via Ethernet with the virtual screen on the PC. Otherwise you need it on the bench in front of you (where the thing you are working on should be).
I have a few other scopes, either inherited or bought for special tasks (sometimes I run long term experiments for customers which need their own gear.) I’ve not mentioned them because they don’t have much bearing on the thrust of this history, except the Pico 5444 which might steal a little of the 6424Es thunder.
To get to the point of all this, I’ve worked through the transitions from analogue CRT based scopes, to digital acquisition scopes, to MSOs and then to what I’ll call computer-based MSOs.
The basic analogue scopes suffer from limited channel capacity and the inability to capture single shots. Early digital scopes suffered from poor analogue sections (still an issue with some) and difficult interfaces.
The LeCroys have pretty much cracked the interface bit - basically they are PCs with a built in scope. They have really nice interfaces but the PC sections seem to hit the reliability. (I don’t have statistical evidence for this, but both my LeCroys have died because the PC sections are faulty – and I don’t have many PCs which have lasted 10 years.)
The R&S RTA4004 and the Keysight MSOX3 and 4 series attempt to be computer based MSOs without a PC and in more typical scope formats. They are all nice scopes but the interfaces are not that good and the small format makes the ergonomics pretty awful.
The Picoscope6424E (at last) – I’m hoping that we have reached the point of a good front end , analogue and digital acquisition (with a 5 year guarantee) but with the computer stuff (interface and non-real time processing) on a real PC with a big screen and a big OS.
Thurlby had a go years ago but there were no PCs then so the DSA524 had to use a scope for a display, the LeCroys show how nice a PC based instrument can be (when working). To my mind the modern R&S and Keysight instruments show that you can’t squeeze what we expect from a modern high performance scope interface into the traditional format.
So I have high hopes for the 6424E – it’s an idea who’s time has come – I’m really looking forward to testing it !