Two tone with UNI-T UTG962E

[cbnation]

This article states that the outputs of a Siglent function generator can be combined with a simple T connector. See Method 1 on https://siglentna.com/operating-tip/generating-complex-waveforms-using-siglents-combine-function-x-series-dual-channel-generators/

I own a UNI-T UTG962E. Can it do the same or can one output damage the other one? I find nothing in the manual.

[ledtester]

The explanation on the Siglent web page is:

In general, the generator has a 50 Ω output impedance so there is no problem with tying the two outputs together externally. All of Siglent’s waveform generators meet this requirement. Below is the explanation based on circuit analysis methodology.

If the outputs of the UTG962 also have 50 ohm output impedance you should be fine.

[Kim Christensen]

If you're worried about it, just use a resistive combiner so the load to each sig gen output is 50 ohms. I think in the Siglent example, the sig gen does the attenuation math for you.

[ledtester]

Update: Apparently my interpretation of the manual page is wrong - and the output impedance of the outputs is always 50 ohms.

Original response

According to page 11 of this UG900 series manual:

https://www.manualslib.com/manual/2595273/Uni-T-Utg900e-Series.html?page=11#manual

the output impedance of each output may be set anywhere between 1 ohm and 999 ohms or set to Hi-Z.

In order to combine the two signals you cannot use Hi-Z. Moreover, if you choose too low of an impedance (like 1 ohm) you run the risk of forcing an output to source or sink too much current which may damage it. An addition consideration is the output impedance of the combined signal. Choosing 50 ohms for the output impedance is nice compromise which will allow the signals to be combined, protect the outputs and provide a reasonable output impedance of the combined signal. That said, choosing 75 ohms or 100 ohms would also be fine choices.

You haven't said what you want the output impedance of the combined signal to be - and perhaps it doesn't matter if, for instance, you are feeding into a high impedance input. But let's say that you want the impedance of the combined signal to be 50 ohms. In that case you could set the impedance of each signal output to be 100 ohms and then the impedance of the combined signal would be 50 ohms.

A final trick you can play is you can combine the signals in different proportions by playing with the output impedance settings. For instance, if you set CH1's impedance to 100 ohms and CH2's impedance to 50 ohms, the signals will be combined in the ratio of 1:2 (CH1 to CH2).

[wasedadoc]

According to page 11 of this UG900 series manual:

https://www.manualslib.com/manual/2595273/Uni-T-Utg900e-Series.html?page=11#manual

the output impedance of each output may be set anywhere between 1 ohm and 999 ohms or set to Hi-Z.

In order to combine the two signals you cannot use Hi-Z. Moreover, if you choose too low of an impedance (like 1 ohm) you run the risk of forcing an output to source or sink too much current which may damage it. An addition consideration is the output impedance of the combined signal. Choosing 50 ohms for the output impedance is nice compromise which will allow the signals to be combined, protect the outputs and provide a reasonable output impedance of the combined signal. That said, choosing 75 ohms or 100 ohms would also be fine choices.

You haven't said what you want the output impedance of the combined signal to be - and perhaps it doesn't matter if, for instance, you are feeding into a high impedance input. But let's say that you want the impedance of the combined signal to be 50 ohms. In that case you could set the impedance of each signal output to be 100 ohms and then the impedance of the combined signal would be 50 ohms.

A final trick you can play is you can combine the signals in different proportions by playing with the output impedance settings. For instance, if you set CH1's impedance to 100 ohms and CH2's impedance to 50 ohms, the signals will be combined in the ratio of 1:2 (CH1 to CH2).

The output impedance of that Uni-T is always 50 Ohm. The menu setting changes only the displayed amplitude of the output that is developed across the load.

[807]

According to page 11 of this UG900 series manual:

https://www.manualslib.com/manual/2595273/Uni-T-Utg900e-Series.html?page=11#manual

the output impedance of each output may be set anywhere between 1 ohm and 999 ohms or set to Hi-Z.

In order to combine the two signals you cannot use Hi-Z. Moreover, if you choose too low of an impedance (like 1 ohm) you run the risk of forcing an output to source or sink too much current which may damage it. An addition consideration is the output impedance of the combined signal. Choosing 50 ohms for the output impedance is nice compromise which will allow the signals to be combined, protect the outputs and provide a reasonable output impedance of the combined signal. That said, choosing 75 ohms or 100 ohms would also be fine choices.

You haven't said what you want the output impedance of the combined signal to be - and perhaps it doesn't matter if, for instance, you are feeding into a high impedance input. But let's say that you want the impedance of the combined signal to be 50 ohms. In that case you could set the impedance of each signal output to be 100 ohms and then the impedance of the combined signal would be 50 ohms.

A final trick you can play is you can combine the signals in different proportions by playing with the output impedance settings. For instance, if you set CH1's impedance to 100 ohms and CH2's impedance to 50 ohms, the signals will be combined in the ratio of 1:2 (CH1 to CH2).

The output impedance of that Uni-T is always 50 Ohm. The menu setting changes only the displayed amplitude of the output that is developed across the load.

Yep. Using my UTG962E right now. Doesn't matter what output impedance it's set to, the signal always halves when it's connected to 50Ω load.

[Kim Christensen]

The output impedance of that Uni-T is always 50 Ohm. The menu setting changes only the displayed amplitude of the output that is developed across the load.

Reminds of some old RF sig gens. Some had the option to display the output setting as EMF (unloaded voltage) vs the more common "potential across a 50 ohm load". It confused me the 1st time I encountered it.

[807]

The output impedance of that Uni-T is always 50 Ohm. The menu setting changes only the displayed amplitude of the output that is developed across the load.

Reminds of some old RF sig gens. Some had the option to display the output setting as EMF (unloaded voltage) vs the more common "potential across a 50 ohm load". It confused me the 1st time I encountered it.

Yeah. The Marconi 2019A sig gens I used at my workplace had the EMF option.