Equipment Reviews.

Siglent® Model 810 Function Generator.

This is not your father's function generator. Using digital synthesis techniques it will generate any waveform you can imagine and probably some you can't. It will generate periodic waves at frequencies from 1 µHz to 10 MHz. No, that was not a typo. The lowest frequency has a period of 1Ms. That's a capitol M for Mega. One million seconds is 16.66 ···kilo minutes, 277.777 ··· hours, or 11.574 days. When the frequency is set to 1 kHz, the amplitude to 1 volt RMS, and the output is terminated in 50 ohms, the distortion on a sine wave is 0.028%. If you have a harmonic distortion analyzer I'm sure you can think of one good use for this generator. There are many more.

The Manual.

Unlike other instruments reviewed under this heading the manual for this instrument is very good; in grammar, style, and clarity. It tells you how to do things in straight forward 1 2 3 step by step instructions.

General.

With power turned off it looks like an oscilloscope with a screen that seems a little too small. After it runs through its boot up and self test routine it looks like the picture below. These are the factory defaults except for one thing. At the middle right of the screen where the picture shows "Load: 50Ω it will show "Load: Hi-Z". The procedure for changing this will be given under the heading " Setting load to 50 ohms."

Close up of front panel.

Something I Don't Like.

The button above the output coaxial connector that is labeled "Output" toggles the output signal on and off. The power on default is "off". I don't know how many times I have set up a circuit, turned on the B+ only to find that the output is less than I am expecting and that it is at a frequency of 60 Hz. After I puzzle over it for a few minutes it dawns on me that I have forgotten to turn on the generator's output. You will note that I forgot to turn it on for the picture. Even if it defaulted to "on" I would never use it because it just disconnects the center contact of the coaxial connector leaving it open. The high input impedance of vacuum tube circuits allows some 60 Hz pickup. This may not be a problem for those who work with lower input impedance transistor circuits. It would be much more useful if the off state had the same impedance to ground as when signal was present. Putting a 50 ohm through termination on the output connector and leaving it there will overcome the open input effect but it does cut the available output voltage in half. Other than that it's perfectly normal.

Soft Keys, Highlighted , and Selected Labels. The New Way.

If you have been around any modern equipment including electronic music keyboards you are familiar with soft keys. They have no labels because they have no fixed functions. The function label for each key is on the screen and can be changed at will by the programmer. That seems possible whether or not his name is Will.

If you look at the picture above you will see that the Amplitude and Offset labels have slightly brighter backgrounds than the Period, High Level, Low Level, and Phase labels. The amplitude and offset labels are said to be highlighted. The Frequency label is much brighter than all the others and this is the Selected Label. Only one label can be selected at a time.

There are two ways to change a parameter such as frequency. Note that the frequency label is selected. If the knob is turned the digit which is under the cursor in the frequency display will be changed one count at a time. Note that frequency appears in two locations on the screen. The value will be changed in both places. The two arrow keys below the knob will move the cursor left and right. If the cursor is not on the left most digit carries or borrows will be generated so the digits to the left of the cursor will change when the digit under the cursor rolls over.

The numeric keypad may be used to set the value of any parameter which is selected. For example when frequency is selected if you type 455 on the number pad the lower part of the screen will change and the digits will appear in side a rectangle as you type them. The soft keys will change their labels and you can select µHz, mHz, Hz, kHz, or MHz. After you make your selection the screen will return to its previous condition and the new frequency will be displayed and the output of the generator will now be at that frequency.

If you press the soft key next to frequency the Period label will be selected. The numerical displays on the screen will change to the value of the period of whatever frequency you have previously entered. Pressing the same key again will switch the selection back to frequency.

If you press the key next to the Amplitude label it will be selected. The label where the selection was before you pressed the key will remain highlighted. If you press the up arrow key below the knob the selection will move back up to frequency or period whichever one was highlighted before you pressed the key. Pressing up and down arrows will jump the selection from highlight to highlight along the left edge of the screen. The knob or numeric keypad will affect whichever parameter is selected when it is used to change the value.

Notice the two sets of parameters Amplitude, High Level, Offset, and Low Level. If you press the Amplitude key then press it again the selection will move to High Level. But notice in the set below the highlight moved from Offset to Low Level. The up and down arrow keys will now move the selection between Low Level and High Level. These set the voltage of the lower and upper peaks respectively of the wave.

The above describes the basic user interface of the function generator. It operates in a similar way regardless of the mode that has been selected.

Available Waveforms.

As you can see from the picture the SDG810 has the usual sine, square, and triangular waves. The duty cycle of the square and triangular waves can be adjusted without effecting the frequency. Not all analog FGs can make that statement. In addition there is a narrow pulse With variable width, white noise, and arbitrary waveforms.

Pressing the "Arb" key takes you into a menu tree from which you can select 48 built in waves including stair step both up and down, ramp, exponential, log, a noisy sine wave and quite a few others that I've never heard of and have no idea what they might be used for. In addition you can import your own waveforms through the USB connector or transfer them from a thumb drive.

It will produce several kinds of modulated waves including AM, DSB, FM, PM, and FSK.

It also does frequency sweeps in which you can set either start and stop frequency or center frequency and sweep width. Sweeps may be linear or logarithmic, up or down. The start of the sweep can be triggered internally, presumably the sweep starts over within a few microseconds of the end of the previous one. It can also be triggered manually. There is a button above the trigger input which when pressed will trigger the sweep. If a TTL compatible signal is fed to the connector it will trigger the sweep.

Setting load to 50 ohms.

  1. Press the "Utility" key.
  2. Press the soft key for "Output Setup".
  3. Press the top soft key to select either "Load" or High Z". In this case you want it on load. The cursor seems to indicate that the value can be changed but on this model it cannot.
  4. Press the "Utility" key again to exit the Output Setup mode.

I think this is the only setting that it remembers when power is turned off.

Note: On more advanced function generator models from Siglent® the value of the output impedance setting may be adjusted. For example if you are working with analog base band video or RF cable systems you might want to set it at 75 ohms.

Note: In this single channel model the "Phase setting is meaningless because there is nothing to compare it against. Presumably The phase function and the output impedance value have been left in the interface subroutine so they don't have to write multiple versions of the operating system for different models. If you ask me this is lazy programming.

conclusion.

I won't end on that note. All in all I am delighted with the performance of this generator. I also own the 80 MHz dual channel version.

Dimensions.

4" x 9" x 11, with bail handle removed. Price: US $282.00 Available from this location.


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