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RAN

Analog discovery 2 waveform generator

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Hello,

 

I am looking to buy Analog Discovery 2 module.

I wanted to know whether the waveform generator can generate arbitrary waveform stand alone? i.e without being connected to a PC and in free running mode powered by external 5v DC power supply?

I want to make the analog Discovery 2 act as a stand alone source for the DuT.

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Hi @RAN

The AD2 can't really be used in standalone mode.
It has no static memory to configure a startup operation, like to generate signal.
When USB cable is disconnected, the VBUS drops and this stops the AUX supply through IC48/IC26
https://reference.digilentinc.com/reference/instrumentation/analog-discovery-2/reference-manual#power_supplies_and_control

A solution would be by powering the AD2 from USB hub, configuring it from software, then disconnecting the PC USB cable.
The AD2 powered from HUB will continue the operate, to output the configured, AWG, Pattern Generator signals, including modulation, triggering options...  positive/negative power supplies

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Hi Attila,

Well i do not strictly want to use the external supply, My main intention is to disconnect from the PC and somehow make the waveform generator output the waveform. The solution you gave me suffices my purpose. Power it via external usb hub, configure it, and then disconnect the PC. If that works then that is good enough for me.

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21 hours ago, attila said:

Hi @RAN

The AD2 can't really be used in standalone mode.
It has no static memory to configure a startup operation, like to generate signal.
When USB cable is disconnected, the VBUS drops and this stops the AUX supply through IC48/IC26
https://reference.digilentinc.com/reference/instrumentation/analog-discovery-2/reference-manual#power_supplies_and_control

A solution would be by powering the AD2 from USB hub, configuring it from software, then disconnecting the PC USB cable.
The AD2 powered from HUB will continue the operate, to output the configured, AWG, Pattern Generator signals, including modulation, triggering options...  positive/negative power supplies

Hi @attila,

Please can you give me an example of what kind of USB hub would be suitable for the workaround you mentioned. I see USB hubs which have a connection from PC to power them up. 

 

Also I have one more question, the input voltage for the scopes is specified to be +/- 25 volts differential. Is this specification for only AC voltage? I want to measure signals which have a dc voltage of ~20 volts and AC amplitudes of 20 volts (0 to 40 volts peak to peak). Is it possible to measure such a signal?

Edited by RAN

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Hi @RAN

The voltage on the differential inputs should be around +/- 25V relative to GND, above 26V it might be distorted.
https://reference.digilentinc.com/reference/instrumentation/analog-discovery-2/reference-manual#scope_input_divider_and_gain_selection

You could use BNC probe at 10x or with the wire kit series resistor and configure in the application corresponding attenuation. Like 1M series resistor with 1M (1.04M) scope input resistance would be a 2x attenuation.

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1 hour ago, attila said:

Hi @RAN

The voltage on the differential inputs should be around +/- 25V relative to GND, above 26V it might be distorted.
https://reference.digilentinc.com/reference/instrumentation/analog-discovery-2/reference-manual#scope_input_divider_and_gain_selection

You could use BNC probe at 10x or with the wire kit series resistor and configure in the application corresponding attenuation. Like 1M series resistor with 1M (1.04M) scope input resistance would be a 2x attenuation.

Ok, so if i have the GND terminal of the oscilloscope probe connected to for example 25 volts dc, then i could measure a signal which has a 25 volts peak i.e maximum voltage of the signal will reach 50 volts, (peak to peak still remains +/- 25 volts volts) , is that correct? Also, can you please comment on what kind of USB hub would i need?

Edited by RAN

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Hi @RAN

I don't wanted to suggest connecting the ground of the AD2 to other DC level, since the ground of the device over the USB is connected to the PC and probably to other equipments too.
A wrong connection in this setup could damage the AD2, PC and other equipments.

Any powered USB hub should do it.

You could also use an USB isolator. These are usually USB 1.1, slow Full-Speed, which make the capture rate lower, but the application and AD2 will be still usable. The record/play rates will be noticeably slower. Such powered isolator will also make the AD2 floating and protect other equipments.

Edited by attila

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6 minutes ago, attila said:

Hi @RAN

I don't wanted to suggest connecting the ground of the AD2 to other DC level, since the ground of the device over the USB is connected to the PC and probably to other equipments too.
A wrong connection in this setup could damage the AD2, PC and other equipments.

Any powered USB hub should do it.

You could also use an USB isolator. These are usually USB 1.1, slow Full-Speed, which make the capture rate lower, but the application and AD2 will be still usable. The record/play rates will be noticeably slower. Such powered isolator will also make the AD2 floating and protect other equipments.

Well, now that i have seen the schematic, allow me to rephrase and clarify. What i meant was connecting Vin_sc1_n terminal to a DC voltage level, since the sc1_n and sc1_p are fully differential inputs. However since the absolute voltage levels are +/- 25 volts, (i was under the impression that +/- 25 volts limits were between the differential terminals), even this scheme will not work. The only solution is to use DC attenuators or drop the signal using simple resistive divider, or through the probes you mentioned before. Thank you for your support.

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