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| university:tools:m1k:alice:desk-top-users-guide [03 May 2021 01:24] – [Multichannel analog interface for the ADALM1000] Doug Mercer | university:tools:m1k:alice:desk-top-users-guide [03 May 2021 19:45] – [Multichannel analog interface for the ADALM1000] Doug Mercer | ||
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| + | **Alternating Sweep Mode** | ||
| The analog Mux interface in ALICE desktop uses a technique common in analog CRT oscilloscopes ( with a single electron beam ) where multiple input channels are switched to the beam deflection circuits on alternating sweeps. This trick requires periodic signals and that each sweep be “triggered” or synced from the same input signal. In this case the triggering signal will be channel A which is not multiplexed. This could be either the AWG generator output of channel A or an external signal input to channel A in Hi-Z mode. Because it is assumed that a MUX is connected to channel B the AWG output function for that channel is set to Hi-Z mode and also since channel B is always a voltage input the current waveform display for that channel has also been disabled. As an example note the screen shot in figure 37. | The analog Mux interface in ALICE desktop uses a technique common in analog CRT oscilloscopes ( with a single electron beam ) where multiple input channels are switched to the beam deflection circuits on alternating sweeps. This trick requires periodic signals and that each sweep be “triggered” or synced from the same input signal. In this case the triggering signal will be channel A which is not multiplexed. This could be either the AWG generator output of channel A or an external signal input to channel A in Hi-Z mode. Because it is assumed that a MUX is connected to channel B the AWG output function for that channel is set to Hi-Z mode and also since channel B is always a voltage input the current waveform display for that channel has also been disabled. As an example note the screen shot in figure 37. | ||
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| + | **Chopping Mode** | ||
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| + | A second Mux interface mode in the ALICE desktop uses another technique common in analog CRT oscilloscopes where two input signal are switched or chopped very quickly to the beam deflection circuits. In the case of the M1k we have a sampling system at 100 KSPS and we can use a square wave from the AWG channel A output to drive the Mux control input at 1/4 the system sample rate, or 25 KSPS. Thus each Mux input “gets” two samples. The software ignores the first of the two samples to allow for settling time and uses the second sample as the data. The software also up-samples the 25 KSPS data back to 100 KSPS using a 4X digital interpolation filter. The software automatically configures the channel A AWG settings. Once set these should not be changed while using the Chop Sweep mode. | ||
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| - | One important feature of the program is that a sync or sweep start pulse is output on the PIO 3 digital output pin just before each analog sweep starts. The sync pulse can be set to either a high going or low going pulse with the selector next to the pulse shaped icon. Using this “reset” pulse would be necessary whenever | + | One important feature of the program is that a sync or sweep start pulse is output on the PIO 3 digital output pin just before each analog sweep starts. The sync pulse can be set to either a high going or low going pulse with the selector next to the pulse shaped icon. Using this “reset” pulse would be necessary whenever |
| ====External DDS based function generators==== | ====External DDS based function generators==== | ||
university/tools/m1k/alice/desk-top-users-guide.txt · Last modified: 26 Nov 2022 17:34 by Doug Mercer