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N5769A error: Couldn't interpret I/O data as single number

Question asked by tehkao on May 31, 2010
Latest reply on Jun 23, 2010 by MattC

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Hi I've been randomly getting these exceptions when using the 5769 power supply:

Caught: {System.Runtime.InteropServices.COMException (0x80040041): Couldn't interpret I/O data as single number.
at Ivi.Visa.Interop.FormattedIO488Class.ReadNumber(IEEEASCIIType type, Boolean flushToEND)

They seem to happen randomly and I am having a hard time reproducing and tracking down what is causing them.

Any help would be appreciated...thanks.

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tehkao Jun 1, 2010 12:39 AM
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Hi just wanted to give some more detail, this seems to happen when I try to read the voltage and current quite frequently:

WriteString(ReadVoltage, true);
ReadNumber(IEEEASCIIType.ASCIIType_R4, true);

I'm reading the votlage and current about once every 0.5 secs. And once every thousands attempts the ReadNumber will throw the exception. Any idea why?
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StevenLee Jun 1, 2010 1:27 PM
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Hi,

So I think the issue is that the speed of the readback is a bit too fast for what this particular power supply can handle. Basically, when you do a READ, the power supply collects a measurement and passes it back to the user over the BUS. There is definite be some latency as the transfer over the BUS, reading, and handling of the value all adds a bit of delay to this overall process. A good experience would be to make this 0.5s bigger to something like 4 seconds and see whether an exception gets thrown. If 4 seconds doesn't produce an exception, then we can be pretty sure that the speed is the issue here.

Steven
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MattC Jun 23, 2010 8:49 AM
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The reading rate here might not be the problem.

One other thing you can try is to use ReadString instead of ReadNumber and see what the actual string being sent back is (in case there are any non numerical values in there for some reason). After you get the string back, you can convert it to a number. If you find anything via this method, please post it here.

Matt
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N5769A error: Couldn't interpret I/O data as single number

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