Scopes for a grand

For the simple tasks, in these days of austerity exactly how much scope can you get for a grand? The short answer is: “A lot more than you could get even five years ago.”

Jason Morris is the UK sales manager for Northamptonshire-based test equipment seller SJ Electronics. “Around the early 2000s, you got a very basic scope. The choice was Tektronix, LeCroy or Agilent; and you paid a premium for the badge,” says Morris.

The alternative was to go to an Asian supplier, such as GW Instek, for an economy scope priced under £500.

And now?

“In last couple of years Agilent, Tektronix and LeCroy have decided to address this market and reduced prices to £500-£1,000: you still pay a premium for the badge,” says Morris.

At the same time, “the quality of Asian products is now the same as the main manufacturers, and the specifications are better”, he says.

So what do you get?

“You get a general purpose bench oscilloscope. You won’t get more than 100MHz bandwidth, and they tend to be two-channel, not four-channel,” Morris says. “If you go for an Asian brand like GW Instek, Hameg or Yokogawa, you are more likely to get 200MHz and four channels.”

Hameg is now owned by the Germany-based test equipment maker Rohde & Schwarz.

Martin Dinmore, sales engineer at Surrey-based test instrument seller Caltest Instruments, also believes the market has become much more price-competitive.

“Tektronix were owners of the commodity scope range with the TDS1000 and 2000. That market place has become more fought for,” he says. “At the low-end you will get 20MHz-40MHz for a couple of hundred euros. For your £1,000, you are looking at oscilloscope with sub-200MHz bandwidth that will mainly be used as a visualisation tool – not aimed at any real in-depth analysis or statistical analysis. Although some measurement and analysis capability would be expected,” says Dinmore. Both Morris and Dinmore see £1,000 as the top-end of the educational market, where schools, colleges and universities buy scopes.

“For the student and educational market, it was quality or quantity, now you get both,” says SJ’s Morris. “The TDS1000-EDU is an example in the £500-£700 range, where Tektronix reduced the cost of basic scopes, and you get a CD that tells you how to use a scope properly.”

Scope makers have high-end ­models to prove that they are good at making test equipment, but they make most of their income from mid-range instruments.

Why are the big boys trying so hard at the bottom?

“The low-end is where they make brand awareness,” says Dinmore. “When guys move out into industry from universities and schools, they will buy what they are used to using. That is why lower end can be so hard-fought.”

Universities, adds Dinmore, are not always limited to £1,000. “Imperial, UCL, Aston and similar research universities will be using extremely high-end scopes in EPSRC-funded projects,” he says.

Educational oscilloscopes have the same limitations as other sub-£1,000 instruments. They are “100MHz bandwidth and below, two-channel predominantly, with a non-Windows interface and an LCD display usually 5-9in across”, says Morris.

“Memory depth is limited, usually to sub-50ksample/channel, and there are a lot around 10ksample/channel. You are slightly limited on trigger options, which is usually linked to limited functionality: basic triggering with basic measurements,” he adds.

“Simple math functions like sum, difference, product and FFT should be included,” says Dinmore. “Measurement parameters should include pulse-width, frequency, rise-time, peak-peak amplitude and RMS, and the measurements should be automated without the need for cursors – although cursors are still something many engineers like to use as a sanity­-check. The user-interface should be clear and intuitive, and there should be a colour display large enough, and with sufficient resolution, to allow easy viewing of multiple waveforms.”

More expensive scopes get 12-15in screens, mega-sample/channel memory and a Windows operating system. Windows allows for PC functionality and a mouse to be added for functional control, and the ability to download software applications to, for example, analyse telecoms signals, decode serial data, and transfer data to an Excel spreadsheet.

“WaveSurfer is LeCroy’s 200MHz scope with Windows and a lot more analysis for £6,835, or the 1GHz version is £9,430,” says Dinmore. That said, at a target price of £1,000, “options for decoding common serial busses are becoming more common place, especially for I2C, SPI, RS232, UART, and in some cases CAN.”

“Industrial users are really looking at £1,500 plus,” says Morris. “Tektronix and Hameg produce pretty sophisticated industrial entry-level scopes for £1,000 to £1,200. Tektronix DPO2000, and Hameg’s HMO range with an external pod offer serial triggering, serial decoding and eight to 16 channels of logic ­analyser.”

A logic analyser? “Agilent did it first, put logic inputs on the front end of scopes. Cheap-and-cheerful logic analysers have pretty much died out. Now serial busses are more predominant, you only want four or five logic channels,” says Morris, adding: “There are also plug-and-play USB logic analysers for PCs.”

So, how low in price can you go for something that an engineer would want to use?

Caltest’s cheapest scope is one from the big three. “Commodity scopes are relatively new for LeCroy. We have LeCroy’s WaveAce101 with 40MHz and two channels for £615,” said Dinmore. “Then we have the GW Instek GDS2062: £695 for two channels, 60MHz 25ksample/ch memory and 1Gsample/s.”

SJ Electronics’ is another one from GW Instek – pictured. “We sell a scope f or £280 for education. We sell them by the bucket-load to universities,” said Morris. “It’s GW Instek’s GDS1052 with colour display, two channels, 50MHz bandwidth and USB connectivity, plus basic maths and FFT on a small footprint. You cannot sell a scope without USB on it.”

USB connectivity ideally gives control over the instrument via a USB host, and the ability to export screenshots, raw waveform data, and set-ups to a thumb drive.

On the subject of USB, what about ‘USB oscilloscopes’ – plain boxes with BNC connectors on one end that use the display and controls of a PC or laptop?

Made in the UK, the £349 PicoScope 2206, for example, is a 50MHz two channel model, and the firm’s 6404B goes up to 500MHz on four channels with 1.25Gsample/s/chan and 256Msample/chan memory for £4,495.

“We sell USB scopes from Pico. They are very neat, and good for laptops, but we find engineers and education usually prefer a real scope with knobs and buttons – it reduces the number of PCs around,” said Morris. “Pico has found a huge market in automotive, and we did sell a lot of PicoScopes to a maths department to show students how to calculate FFTs. They do the calculation, then see the actual signals.”

Dinmore again sees a similar picture. “Without a screen and controls, their costs are much lower,” he said. “I certainly wouldn’t write them off as competitors, their bandwidth is coming up. It is just that some users want equipment they can get out of the cupboard and turn on.”

Back with conventional oscilloscopes, some low-end types offer surprisingly high sample rates compared with their input bandwidth. “Nyquist doesn’t give you anything like enough bandwidth,” said Dinmore. “You need at least 5x, and 10x is nice to have because the more points you have at the edge, the more accurately you can represent the edge.”

The reason that some low-end scopes easily meet 10x, according to Dinmore, is that their makers have their own fast front-end sampling and analogue-to-digital converter (ADC) chips.

“Although this is not the case for everybody, some high-end manufacturers will be using two front-end chips per channel in their high-end scopes, and then in their lower-end scopes feeding all four inputs into one similar ADC,” he explained.

So, a lot of oscilloscopes are available for £1,000, with far more bandwidth and far more features than a decade ago.