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Review: Siglent SDS2104 4x100MHz 2GSs/s Mixed Signal Oscilloscope By JIM ROWE While Siglent’s SDS2104 mixed-signal oscilloscope may not be their newest scope, it still offers a wide range of useful features. Now, with optional extras being included free of charge, it’s exceptional value for money. I t wasn’t that long ago that a basic two-channel 100MHz bandwidth digital oscilloscope sampling at no more than 500MSa/s would set you back more than $5000. But that was when DSO technology was very new and the market was dominated by two big US firms. Since then the technology has galloped away and quite a few other firms have joined the market, many of them based in China. Siglent started up in Shenzhen, China (near Hong Kong) in 2002, and launched their first ADS7000 DSO in late 2005. By 2007, these were selling in both the USA and Western Europe at the rate of 10,000 units per year. Since then, Siglent has been releasing a steady stream of high performance scopes. The SDS2104 is part of their SDS2000 series of “Super Phosphor” oscilloscopes, launched in late 2013. Last year, this series was partially superseded by the SDS2000X series, although the differences between the two are not dramatic. Models like the SDS2014 have continued to sell well, especially since some of the previously optional extras are now being included at no extra charge. Scope 1: this rather busy screen grab shows all four analog channels measuring various different waveforms, with the eight digital channels also enabled. Details of the timebase and vertical settings are at the right edge of the screen. 88  Silicon Chip It’s because models like the SDS2014 offer such good value for money that we’ve chosen to review it here, rather than its newer equivalent, the SDS2014X (which carries a significantly higher price tag). Main features The Siglent SDS2000 series comes with an analog bandwidth of 70MHz, 100MHz, 200MHz or 300MHz with either two or four channels. So the SDS2014 with its four 100MHz channels is in the middle of the range. Like all models in the series, the SDS2014 offers a maximum real-time sampling rate of 2GSa/s, although this only applies when a single channel is being used (the X series offers the full sampling rate regardless of the number of channels in use). The memory depth is quite impressive though, at 70Mpts (vs 140Mpts for the X series). It also boasts a fast signal capture rate of 110,000 waveforms/sec, while the X series offers 140,000 wfm/s. Other key features of the SDS2014 include those associated with Siglent’s Super Phosphor (SPO) technology: a siliconchip.com.au Key Features • • • • • • • • 256-level intensity grading waveform display plus a colour temperature waveform display. Both of these are designed to allow clearer identification of brief events as well as indicating the probability distribution of a displayed waveform. There’s a neat hardware-based zoom function (see Scope 3), which lets you zoom into any part of a captured waveform to examine and measure all of its details. It has a wide range of triggering options, including edge, slope, pulse, video (including HDTV), window, interval, dropout, runt and pattern triggering. There are also five serial trigger and decode functions, covering serial data protocols for I2C, SPI, UART/ RS232, CAN and LIN. For automatic measurements on analog signals, there’s a choice of 14 different voltage measurements, nine different time and duty cycle measurements and another nine inter-channel time delay measurements. It’s also easy to make custom measurements using vertical and horizontal cursors. siliconchip.com.au Four 100MHz channels Sample rate of 2GSa/s (single channel) Signal capture rate of 110,000 waveforms per second Memory depth of 70Mpts 8-inch 800x480 24-bit colour TFT-LCD display 256-level intensity grading waveform display 25MHz arbitrary waveform generator 8-channel logic analyser There’s a good selection of waveform “math” operations. As well as the usual addition, subtraction, multiplication and division it includes Fast Fourier Transform (FFT), differentiation, integration and square root. Cursor measurements can be used on any of these operations as well. Other features of the basic SDS2000 series include a 200mm (8”) diagonal TFT-LCD colour display with 800x480 pixel resolution, an English or Chinese user interface with a built-in help system and the ability to save set-ups, waveforms, screen images and CSV data files in either internal memory or on a USB thumb drive plugged into the instrument’s front panel. It also has the ability to print the screen image directly to a PictBridge compatible USB printer, plugged into the USB type-B socket on the rear panel. Also on the rear panel is a LAN (VXI-11) socket for communication with a PC plus a pair of BNC sockets; one external trigger input and the other for either trigger output or Pass/ Fail test result status. Incidentally, the SDS2104, like all of the other models in the SDS2000 series, responds to SCPI remote control commands fed to it via either a USB or LAN cable. Other handy features include the ability to update the firmware, to do various self tests, to change the settings for the screen saver, to set the date and time for the built-in RTC and the ability to do self-calibration. While that covers the main features, there are extra “bonus” features. Bonus features First of all, there’s the inbuilt 8-channel logic analyser. This works in conjunction with a logic sampling probe (SPL1008, currently bundled Scope 2: this heat map display of a frequency modulated sinewave shows how the scope captures thousands of waveforms per second and varies the pixel colour based on how many captured waveforms cross a given point. November 2016  89 Scope 3: this capture shows how the large amount of standard memory allows zooming into the waveform while still showing fine details of the signal. Scope 4: here the I2C protocol decoding has been enabled; the clock and data signal traces are shown, along with the decoded hexadecimal data below and, in table form, above. with the SDS2104), which plugs into a rectangular socket at the lower centre of the front panel and has nine flying input leads; eight signals plus earth. In comparison, the newer X-series models have an optional 16-channel MSO function, which needs a matching 16-channel probe (SPL1016). Among the options available in MSO mode are the ability to set the triggering threshold to suit TTL, CMOS, LVCMOS3.3 and LVCMOS2.5 logic levels, plus a custom option to allow setting the threshold to anywhere between -3V and +3V. There are also a number of options regarding display of the digital channels. For example, when you have activated the serial trigger and decoding function, you 90  Silicon Chip can display each channel (or a group of channels) in terms of its decoded binary or hex value as well as its waveform (see Scope 4). The sampling rate for the MSO digital channels is quoted as 500MHz, and the status sampling rate as 60MHz. The maximum data rate for a single channel is 120Mbps, while the pulse width resolution is 15ns. In short, although the MSO function might have only eight channels, it should be quite useful for many common testing applications, especially when used together with the SDS2104’s serial decoding functions. The AWG/function generator The arbitrary waveform and func- tion generator provides a choice of nine different inbuilt waveforms: sinewave, square wave, ramp (triangular/rising or falling sawtooth), pulse, noise, cardiac, Gaussian pulse, exponential rise and exponential fall. There’s also a DC option which adjusts the offset applied to any of the previous functions, plus support for arbitrary waveforms to be loaded into the SDS2104 from a PC, using Siglent’s EasyWave software. The same software can be used to create the waveform, either from scratch or by downloading an existing standard waveform from the SDS2104 and editing it as desired. EasyWave can be downloaded from Siglent’s US website (www.siglentamerica.com) but note that before it can be run you also have to download and install NI-VISA 15.0.1 from the National Instruments website at www. ni.com/download/ni-visa-15.0.1/5693/ en/ This provides the drivers necessary for USB (or LAN) communication with the SDS2104. The waveform generator has only one output channel but its specs are quite impressive. The sampling rate is 125MSa/s, with a waveform length of 16K points and a vertical resolution of 14 bits. Maximum output frequency is 25MHz, with a frequency resolution of 1µHz. The output amplitude can be set to any level between 4mV and 6V peak-to-peak for a high impedance load, or from 2mV to 3V peak-to-peak for a 50Ω load. When sinewave output is selected, the frequency can be set to anywhere between 1µHz and 25MHz. The upper frequency limit drops to 10MHz when you select a square wave or rectangular pulse, or to 5MHz if you select cardiac, Gaussian pulse or the exponential rise or fall waveforms. Selecting a ramp waveform makes it fall even further, to 300kHz. It’s worthwhile noting with respect to the square wave and pulse options that the duty cycle of the square wave output can be varied between 20% and 80%, with rise and fall times of less than 24ns. The pulse width can be adjusted between 48ns and 1ms, with a jitter level of 8ns. So the built-in function and AWG generator with its 25MHz range and 14-bit vertical resolution should be very useful in a wide variety of testing applications. Incidentally, Siglent have an opsiliconchip.com.au Front view: each channel has its own set of vertical controls while the remaining buttons are laid out in a clear and logical manner (in fact, quite similarly to our venerable Agilent scope). On the screen, you can see a chopped sinewave being produced from the internal arbitrary waveform generator, as described in the text. tional SPA1010 wideband 10W amplifier which can be used to boost the output of the SDS2104’s waveform generator as well as any of their other function/AWG generators. The SPA1010 has a rated -3dB bandwidth of 1MHz and can deliver 10W into an 8Ω load at any frequency between This optional isolation module allows up to two channels to have independent ground references. siliconchip.com.au 500Hz and 200kHz. Power analysis The final bonus feature currently bundled into the SDS2104 is a firmware module to perform Power Analysis of switchmode power supplies. This module can perform quite a few SMPS tests, including: • seven tests at the AC line input (power factor, true power, apparent power, current harmonics, crest factor, inrush current and phase angle); • three analysing the device itself (switching loss, di/dt and dv/dt slew rates); • nine analysing the switching performance (average, RMS, period, frequency, positive and negative pulse width, duty cycle, rise and fall times); • one testing output ripple; • two measuring turn-on and turnoff times; • one for transient response, and • three for determining overall efficiency (Pout, Pin and Pout/Pin). To make full use of this module, you need to acquire various external items, though. At the very least you’ll need an isolating high-voltage probe, plus a current probe. Siglent can provide a two-channel isolating HV probe with a bandwidth of 1MHz, powered from the DSO itself via the front-panel USB connector. They can also provide a wideband (40MHz) 30A AC/DC current probe, the CP5030, although this does cost about twice as much as the SDS2104 DSO itself. There’s also a Power Analysis Deskew Fixture (DF2001A), which can be used to compensate for any time delay difference between the voltage and current probes, to improve measurement accuracy. What we found Despite its high performance and generous 200mm-diagonal screen, the SDS2104 is fairly compact (352 x 224 x 112mm) and modest in weight November 2016  91 The rear panel carries the mains input socket, Kensington security lock, trigger in/out BNC connectors, USB host port and Ethernet interface, for remote control. The integrated carry handle and feet can also be seen. The trigger output can also be configured as a pass/fail output via the front panel user interface. (3.6kg). It also appears to be sturdily built, which should augur well for reliability. We tested the bandwidth of the four main analog input channels and they all proved to have an upper -3dB frequency above 116MHz, with one channel showing a figure of just over 140MHz. Very comfortably above the rated 100MHz, in other words. We were very impressed with the wide range of trigger functions and waveform maths operations, and also the variable trace intensity/persistence and colour grading functions provided by Siglent’s SPO technology. We were impressed by the wide range of serial triggering and decoding options, and the way they enhance the mixed signal aspect of the SDS2104. It does take a while to get familiar enough with setting these options, but once you do it’s easy to see 92  Silicon Chip that the instrument should be very handy for tracking down tricky problems involving I2C, SPI, CAN or LIN data transactions. The built-in waveform/function generator turned out to be easy to use, and we were impressed with the clean waveforms resulting from its 14-bit resolution. For many users, the function generator section may well provide all that is needed in terms of test signal generation up to 25MHz. We’re not sure how useful the AWG feature would be but we did try downloading and installing both NI-VISA and Easywave on a PC, and then downloading a sine waveform from the SDS2104 and changing it into a chopped waveform like that achieved by a Triac. That proved to be quite easy and when we then loaded the result back into the SDS2104’s AWG, we could generate the chopped waveform in short order. The Power Analysis feature is fairly specialised in application, coupled with the need to acquire various extra hardware items (some of them quite expensive) in order to put it to use. Still, for those who are involved in testing SMPSs it could make the SDS2104 particularly good value for money. In summary, we found the Siglent SDS2104 100MHz DSO/MSO an excellent performer and exceptional value for money. It’s currently available with all the above features for less than $1900 including GST. You can get it from Siglent’s Australian distributor, Trio Test & Measurement Pty Ltd. For more details, visit www. triotest.com.au or e-mail sales<at>triotest.com.au Alternatively, phone them on 1300 853 407. SC siliconchip.com.au