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Why are M series missing points in Matlab when both AI and AO are running?

Hi!

I have a set of scripts I have been using on various machines, with various version of Matlab and the data acquisition toolbox and E-series card and always worked (PCI 6052E, PCI 6040E)

I recently had to use them on a system with an M serie DAQ installed (PCI 6221) and I had weird signal: while the singal coming into the BNC of the breakout box is around -6V, the card sometimes displays jumps to 0 for one point, synchroneously on both channels I'm recording, as if the card was missing a point and replacing it with 0. The 'remplacement point' is always the same value, for both channels, and no missing data error is issued.

 

This happens for both a PCI 6221 and a 6251 I tried with the same configuration, but not with a E serie (PCI MIO 16E1).

This only happens for the M series when I have both an AO and an AI running at the same time.

 

I'm not trying to push the card over its limit: my acquisition and output rates are 5kHz (max sampling rate is 250kHz, max output even more according to the specs), and the RAM on this computer is 2GB vs 2 AI channels, native type : double, max 75 000 points per channel.

 

Is there anything I can do to prevent that problem?

 

Specs of the system:

Hardware:

PCI 6221, breakout box BNC 2110

Computer: Windows XP SP3, 2 GB RAM, Celeron 2.53GHz

 

Software

Matlab 2008a, Data acquisition toolbow 2.12

 

Acquistion system:

AI:

2 channels

15 000 to 75 000 sample/channel (same problem in both cases: missed points are random, and mostly at the beggining of the recording when there, for both conditions)

5kHz sampling rate

Hw Trigger on PFI1 (from a digital output on the card)

 

AO

2 channels

5kHz sampling rate

Hw Trigger on PF6 (from a digital output on the card)

 

DIO (for the triggering)

1 line output, which output is connected to PF1 and PF6 on the breakout box

 

The AI is logging and the AO is sending with the following scheme:

 

start([ai ao]) %%sets AI and Ao Running 'on'

putvalue(dio,1) %Triggers the AI and AO

 

 This works like a charm for E series and synchronizes the input and the output.

 

 

Thank you for any help!

Erwin

Message Edité par Erwin-BU le 09-24-2008 01:00 PM
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Hi Erwin,

 

As you discuss it with my working colleague by calling the phone assistance; using LabVIEW, there is no point missing.

I send here the VI my colleague sended to you, in case it would help anyone which might encounter the same kind of problem.

 

Best Regards,

 

Flo

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