Maximum measuremments on a 4072

[MJR]

Hi there,

I was wondering what was the maximum number of measurements that the 4072 can store before I have to call Multipoint Fetch? The spec says it has 1Mb of onboard memory but that does not tell me how many measurements I can make. 

Thanks.

[tnek]

Hi MJR,

I was wondering if you could give a little more information about what exactly you are looking for (i.e. what resolution are you using?). I was also wondering where you found the onboard memory specification to ensure we are on the same page. The onboard memory will not be the limiting factor of how many samples you can acquire from a multipoint fetch since the NI-DMM driver allocates a large buffer in software. The transfers from the onboard memory to the software buffer are all handled internally by the driver. You can manually set the software buffer size by using a NI-DMM property node and selecting MultiPoint Acquisition » Advanced » Buffer Size. This value is set by the driver if the default settings are used. Hopefully this helps a bit.

Regards,

Kent

Applications Engineer

[MJR]

Hi there,

I am using the 5.5 digit resolution. MY goal here is to use the 4072 to make 64k measurements from a DAC. I'd like to trigger the 4072 everytime I change codes, so a total of 64k measurments. I took the 1Mb nummber off of the 4072 datasheet.The goal is to read back the buffer at the end off the 64k measurements.

Also, what is the average storage size for a single reading. I can use this info to set a software buffer size accordingly. 

Regards,

MJR

[tnek]

Hi MJR,

Thanks for the clarification but I am still having a hard time finding where you got that specification for onboard memory. Would you be able to send me a link to that? In addition, the buffer size property is set by the number of samples not by the total size of samples. See this description from the NI-DMM Help.

Multi Point Acquisition:Advanced:Buffer Size Property

Specifies the size in samples of the internal data buffer. Maximum size is 134,217,727 (OX7FFFFFF) samples. When set to Auto (-1), NI-DMM chooses the buffer size.

Since the driver configures all of this automatically, you will not have to worry about doing everything yourself, you can jsut ensure that the buffer size is equal to or larger than 64k. 

Regards,

Kent

Applications Engineer