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Test equipment review: By NICHOLAS VINEN Siglent SDG1050 50MHz 2-channel Function Generator This low-cost arbitrary signal generator is compact and easy to use. It has outputs for two independently configurable waveforms, including sine, square, triangle, pulse, noise or just about anything you can come up with, at frequencies up to 50MHz. It can also be used as a frequency counter. T HE SIGLENT SDG1050 is a lowcost 50MHz arbitrary function generator. It is a compact instrument (229 x 105 x 281mm) which has all the usual features that you would expect in this type of device. Its manufacturer, Siglent, is the largest oscilloscope manufacturer in the world. Haven’t heard of them? That’s OK; neither had we. Their name isn’t well known because they are an original equipment manufacturer (OEM) and most of their scopes are sold under other brands. Siglent and a couple of other Chinese manufacturers make most of the entry-level scopes for name brands. siliconchip.com.au So they obviously know how to make test gear and that is confirmed as soon as you open up the box; the build quality of the SDG1050 is top notch and it feels solid and well-made. There are some nice design touches; for example, the bail doubles as a carrying handle and the stand has indentations for your fingers which give a reliable grip for carrying the instrument. And there are rubber “feet” on all the corners as well as plastic feet on the back, so you can stand the instrument in just about any orientation without damaging it or the surface it’s on. They’ve also included a great bonus feature; if you aren’t using the trigger input, you can also use the unit as a frequency counter which can operate in the range of 0.1Hz-200MHz. This is accessed through the on-screen “utility” menu and you get a few options such as whether to measure frequency, period, pulse width or duty cycle, what the reference level is for counting pulses, whether it is AC-coupled and also optionally enable a low-pass filter. Signal generators In addition to arbitrary waveform shapes that you can define on one or two channels, it has various built-in waveform shapes such as sine, trianApril 2013  81 Fig.1: the output of the SDG1050’s two outputs showing how they can be used independently. Channel 1 (yellow, at top) is producing a 100kHz sinewave which is being frequency modulated with another sinewave with a longer period. At the same time, channel 2 is performing a sweep. gle, sawtooth, square and white noise. It can generate signals with amplitudes from 4mV peak-to-peak up to 20V peak-to-peak into a high impedance load or half that into 50Ω. Channel 2 is limited to 6V peak-to-peak or 3V for 50Ω. The signals can be swept, output in bursts or modulated using AM/FM/ PM/ASK/FSK/PWM. The modulation source can be an external analog signal or it can be an internally generated waveform of just about any type the unit supports. The sampling rate of the unit we are reviewing is 125MS/s and the voltage resolution is 14 bits. Maximum arbitrary waveform length is 16,000 samples or 256k samples if you disable one channel. As well as defining your own waveform, there are 48 common types built in such as cardiac, exponential rise or fall, Gaussian, various FFT window shapes, x2, x3 and so on. Maximum signal frequency is as follows: 50MHz for sine, 25MHz for square, 5MHz for arbitrary/pulse and 300kHz for triangle/sawtooth/ramp. To use the trigger output, signal fre- Fig.2 this shows two of the built-in arbitrary waveforms that you can select. The yellow trace at top is generating an x3 function at 1kHz while the other channel in blue is producing the “earthquake” function at the same frequency. The sync output has been enabled and the pulses from this are shown in green. quency must be no more than 2MHz. Because the output is DC-coupled, very low frequency signals are possible, down to 1µHz in most modes. That also means an adjustable DC offset can be applied to the output. The two outputs are totally independent and can be set up in any way that you like. It’s possible, however, to copy the settings from one output to another if you want to set them up similarly. As you would expect of such a device these days, it has USB support. That includes both a host port to which a flash drive can be connected to save and load settings and waveforms and a device port (on the rear panel) which can be used to connect the unit to a computer for control. For direct control, the device has a 9cm (3.5-inch) colour LCD, five “soft buttons” next to the display, a numeric keypad, rotary encoder knob/pushbutton, arrow keys and a number of mode pushbuttons, many of which are illuminated when that mode is selected. The two output BNC sockets are on the front, adjacent to pushbuttons Issues Getting Dog-Eared? Keep your copies of SILICON CHIP safe, secure & always available with these handy binders Order now from www.siliconchip.com.au/Shop/4 or call (02) 9939 3295 and quote your credit card number or mail the order form in this issue. *See website for overseas prices. 82  Silicon Chip REAL VALUE AT $14.95 * PLUS P &P which can be used to quickly enable or disable that output. Besides the USB host port, all the other sockets are on the back and that includes four BNC sockets: the trigger output, trigger input, 10MHz reference clock input/ output and external modulation input. There is also an earth point, the IEC mains power socket and the aforementioned USB device port. Interface So those are the specs but is it easy to use? Well, we found the interface a bit confusing when we first had a go at it (not bothering to read the user manual as usual) but very quickly figured it out. Most functions are controlled through a combination of the soft buttons (to select items from the on-screen menu), the mode buttons and the numeric keypad. Say you want to generate a 1MHz sinewave with 50kHz frequency modulation by a triangle wave of 1kHz and generate a sync output. The procedure is as follows: (1) Press the CH1/2 button to select the desired output channel; (2) Press the sine button; (3) Press the “1” button on the keypad, then the soft button labelled “MHz”; (4) Press the “Mod” (modulation) button; (5) Press the “Shape” soft button until it reads “Triangle”; (6) Press the “Type” soft button until it reads “FM”; (7) Press the “1” button on the keypad, siliconchip.com.au then the soft button labelled “kHz”; (8) Press the “FM Dev” soft button, then type “50” and press the soft button labelled “kHz”; (9) Press the “Utility” button, then the “Output Setup” soft button; (10) Press the “Sync” soft button, then “State” until it shows “On”, then “Done”. That’s all quite easy and most jobs are similarly straightforward once you’ve played with it for a few minutes. The interface therefore gets a thumbs up. What we did find a bit odd though is that sometimes a menu pops up which prompts you to select from a list of options and you can then use the rotary knob to select one. But then if you press the knob in, nothing happens. You have to use a soft button labelled “Select” to make the selection when the knob pushbutton would have been more convenient. But that’s a minor criticism. The rear panel carries four BNC sockets for the trigger output, trigger/ frequency counter input, 10MHz reference clock input/output and external modulation input. There’s also a USB device port (eg, to connect a PC to control the device), an earth point and an IEC mains socket. The Siglent SDG1050 comes with a printed user manual and a CD for installing the Easy-Wave waveform editing software on a PC. Also supplied are a USB cable and a power cord. PC software Windows software called “EasyWave” is supplied to edit arbitrary waveforms which can then be loaded onto the signal generator. These can be hand-drawn point-by-point or can be based on mathematical functions, including trigonometric, exponential and logarithmic functions. They can be transferred directly using the supplied USB cable or via a flash drive. Performance So how does it stack up? In fact, it performs similarly to other arbitrary waveform generators with this type of frequency range and capability. Sinewave THD+N at 1kHz is around 0.05% (20kHz bandwidth) and doesn’t vary a great deal with level although it does climb at very low output levels, to around 0.5% at 4mV peak-to-peak – quite impressive given how little signal there is at this output amplitude. The signal-to-noise ratio is 96dB at maximum output level (20V peak-topeak) and drops at lower output levels, as you would expect. That’s if you switch between outputting a signal and DC. There’s an extra 10dB of SNR if you switch the output off entirely. As for square-wave performance, there is a little visible overshoot at 1MHz but the output is still basically square. By 10MHz there is some apparent rounding and at 25MHz it is somewhat trapezoidal. That’s pretty much to be expected for an instrument siliconchip.com.au with an analog bandwidth of 50MHz. Voltage accuracy is good if you set the load impedance correctly; with the output set to 4V in high-impedance mode, our scope gave us a reading of 4V while a true RMS multimeter gave 3.99V; pretty much spot on. Frequency accuracy is specified as ±100ppm, ie, ±0.01% within the first year when operating with an ambient temperature of between 18-28°C. That means it makes quite a reasonable frequency reference too. If that isn’t good enough, you can simply feed in a more accurate 10MHz reference clock from another piece of equipment. Conclusion The Siglent SDG1050 does what it says; it’s a capable dual-channel arbitrary function generator with decent performance and good build quality. It costs $595 + GST and is available from Trio Smartcal. For further information, visit www. triosmartcal.com.au or phone them at 1300 853 407. You can also e-mail sales<at>triosmartcal.com.au for more information or to make a purchase. Trio have some other options too, such as the 25MHz SDG1025 which has quite similar features to the 1050 (but 20MHz analog bandwidth) for $439 + GST. The more capable 80MHz SDG5082 is $795 + GST. These are all competitive offerings from Siglent and we have no hesitation in recommendSC ing them. April 2013  83