How much power can the AWG on an MSO5000 scope output?

[ballsystemlord]

AWG (Arbitrary Waveform Generator.)
I searched both the datasheet and the manual without success.

I don't imagine it would be much, but at the same time I don't want to accidentally overload the poor thing and break the oscilloscope.

How much power can the AWG on an MSO5000 scope output?

Thanks!

PS: You're welcome to post about other scopes AWGs' capabilities as well. It might prove helpful to others.

[RAPo]

From the datasheet, each channel: 20 mVpp~5 Vpp (HighZ), 10 mVpp~2.5 Vpp (50 Ω).
Resolution 100 uV or 3 bits (whichever is greater).
and accuracy of ±(2% of setting+1 mV) (Frequency=1 kHz).

[TimFox]

From that, one calculates the maximum short-circuit output current as 5 V (pk-pk) / 50\$\Omega\$ = 100 mA (pk-pk), but the output stage might be capable of only half of that current.

[ballsystemlord]

I never guessed to look at the amplitude section.
Thanks again!

[ballsystemlord]

I also never thought I'd be such a small value as 1/2 watt. I was thinking more like 10 watts or something so it'd be very useful as an AWG tool. But I guess it's more like a nice tacked-on feature.

[tautech]

I also never thought I'd be such a small value as 1/2 watt. I was thinking more like 10 watts or something so it'd be very useful as an AWG tool.

Inbuilt AWG's are notorious for their low output drive capabilities so if you need better you are much better served with a standalone AWG, some of which can supply 200mA in DC output mode.

But I guess it's more like a nice tacked-on feature.

No, it's just the nature of the beast. 

[radiolistener]

The most sensitive input of oscilloscope is when it switched to 50 Ω. Usually there is absolute maximum rating for oscilloscope 50 Ω input mode is 5 Vrms. It means that absolute maximum rating for oscilloscope input in 50 Ω mode is P = 5*5/50 = 0.5 Watt.

Note, this is not the max measurement rating, this is the max rating which is guarantee that device can survive it. If you exceed it even for a little, it can leads to device damage.

For 1 MΩ mode input the absolute maximum rating is higher, but it depends on the frequency. While for DC it can be up to 400 V, for a high frequency its limit will be much smaller, above 100 MHz it can be about 40 V or even less than that. Which is about 40*40/1000000 = 0.0016 Watt.

As you can understand high impedance input consume much smaller amount of power. For example if your input is switched to 1 MΩ mode and there is 400 V DC on the input, it leads to a power consumption about P 400*400/1000000 = 0.16 Watt.

So, you can assume that absolute maximum rating for 1 MΩ oscilloscope input is:
- about 0.16 Watt for DC current
- about 0.0016 Watt for AC current at high frequency

And for 50 Ω oscilloscope input absolute maximum rating is about 0.5 Watt.

Regarding to AWG, usually they have output up to 25 Vpp = 12.5 Vpk for open output. For 50 Ω load it will be 12.5/2 = 6.25 Vpk and output power will be 6.25*6.25/(50*2) = 0.39 Watt.

This is close enough for absolute maximum rating 0.5 Watt for 50 Ω oscilloscope input, but still within allowed range.

For 1 MΩ load the maximum output power of AWG will be much smaller: 25*25/(2*1000000) = 0.00031 Watt.

So, if your AWG has 50 Ω output and it's maximum output voltage doesn't exceed 25 Vpp for open output (often called HiZ), you can assume that it cannot damage your oscilloscope input for both impedance modes 1 MΩ or 50 Ω.

[Protegimus]

From the datasheet, each channel: 20 mVpp~5 Vpp (HighZ), 10 mVpp~2.5 Vpp (50 Ω) - at 50Ω impedance it is only 2.5 Vpp output, so limited to 50 mA (pk - pk) 0.125W.

I was just looking at this for doing some basic transistor curve testing!

From that, one calculates the maximum short-circuit output current as 5 V (pk-pk) / 50\$\Omega\$ = 100 mA (pk-pk), but the output stage might be capable of only half of that current.

Standalone is yet another expense and more benchspace. MSO5000 internal generator is pretty decent for what it is (and compared to competitor offerings).
You can easily put the signal through a very inexpensive buffer/gain stage if you want more output.

I also never thought I'd be such a small value as 1/2 watt. I was thinking more like 10 watts or something so it'd be very useful as an AWG tool.

Inbuilt AWG's are notorious for their low output drive capabilities so if you need better you are much better served with a standalone AWG, some of which can supply 200mA in DC output mode.

But I guess it's more like a nice tacked-on feature.

No, it's just the nature of the beast. 

[ballsystemlord]

So an AWG attached to an Oscilloscope is designed not to overload the scope if it's shorted directly to the input of the Oscilloscope and that is the reason for the lower power rating of said AWG?

[bdunham7]

I don't imagine it would be much, but at the same time I don't want to accidentally overload the poor thing and break the oscilloscope.

Do you mean break the AWG section or the oscilloscope input section?  Neither will happen, but for different reasons.  The AWG should have a 50R output impedance and be able to operate into a short circuit without issue.  If its maximum voltage is 5V (which I think it is) then you'll see a current of 100mA into a short circuit.  This is a peak or DC value, not RMS, but for DC or a square wave these are the same value.  The inputs of your scope are 1M--there's not a 50R option--so it would take hundreds of volts to damage that--less at HF, but nothing your AWG puts out is going to harm it.  If you did have a 50R input, say on a different scope, those are typically rated for 5V_RMS and your AWG would be putting 2.5V at most into a 50R load, so only 1/4 or less of what the input could tolerate. 

In short, you shouldn't be able to break anything with the AWG alone.

So an AWG attached to an Oscilloscope is designed not to overload the scope if it's shorted directly to the input of the Oscilloscope and that is the reason for the lower power rating of said AWG?

No, not really--it's just a less expensive, lower-power version.  It actually isn't super cheap or easy to make the output of an AWG go to +/-10 volts, and even a more powerful full-featured AWG isn't going to harm your scope.

[BeBuLamar]

If you want more power and don't need very high frequency you can connect the output of the AWG to an audio power amplifier which can deliver something like 100W at reasonable cost.

[ballsystemlord]

I don't imagine it would be much, but at the same time I don't want to accidentally overload the poor thing and break the oscilloscope.

<snip>
I meant the AWG portion.
I rather thought that was implicit since the input is 1Mohm.

So an AWG attached to an Oscilloscope is designed not to overload the scope if it's shorted directly to the input of the Oscilloscope and that is the reason for the lower power rating of said AWG?

No, not really--it's just a less expensive, lower-power version.  It actually isn't super cheap or easy to make the output of an AWG go to +/-10 volts, and even a more powerful full-featured AWG isn't going to harm your scope.

I was actually trying to understand what was meant by, "...the nature of the beast." Full quote below.

But I guess it's more like a nice tacked-on feature.

No, it's just the nature of the beast. 

[tautech]

I was actually trying to understand what was meant by, "...the nature of the beast." Full quote below.

But I guess it's more like a nice tacked-on feature.

No, it's just the nature of the beast. 

Inbuilt AWG's provide very limited drive and functionality, that can be fine when you don't need much of either but a standalone AWG performs at another level of functionality.

[radiolistener]

So an AWG attached to an Oscilloscope is designed not to overload the scope if it's shorted directly to the input of the Oscilloscope and that is the reason for the lower power rating of said AWG?

No, it just designed to produce good quality signal without very expensive and heavy power amplifier.

As said above you can use audio power amplifier if you want to get high power low frequency. For a high frequency power amplifier is more complicated and expensive. You can use short wave power amplifier with 100-200 Watt output, but they usually very sensitive to a load impedance mismatch, so if you want to use it with load other than 50 Ω it will be an issue because it will lead to trigger protection circuit or even damage of amplifier.

Another way for high frequency is to use short wave tube power amplifier, they allows to get up to 2000 Watts and more, but it's not safe, because they are working at high voltage (several kilovolts) and dangerous current.

if you want 5-10 Watt power, there are available power amplifiers for measurement purposes, such as Rigol PA1011.

[TimFox]

A typical free-standing AWG (Rigol DG900) can output 10 V pk-pk into 50\$\Omega\$ up to 10 MHz, falling to 1 V pk-pk above 60 MHz.
A 10 V pk-pk sine wave into 50\$\Omega\$ is 250 mW = +24 dBm.
If you need more power than that, then an appropriate amplifier is required.