Delay time cDAQ 9181 measuring current

[mcidor]

Hi,

I am using .NET libraries to communicate with a cDAQ 9181.

In the begining I was measuring Voltage and everything worked fine but due to a electrical design now I have to measure current.

The problem I am facing now is that IT IS VERY SLOW, It takes up to 2 seconds to start measuring.

myTask.AIChannels.CreateCurrentChannel(physicalChannelName, "", (AITerminalConfiguration)(-1), minimumValue, maximumValue, AICurrentUnits.Amps);

myTask.Timing.ConfigureSampleClock("", rate, SampleClockActiveEdge.Rising, SampleQuantityMode.ContinuousSamples, 1000);

Is this normal?

Am I doing something wrong?

Thanks for your ideas.

Regards.

[nyc_(is_out_of_here)]

cDAQ 9181 is just a chassis with one open slot.

Which C-series module are you using?

[mcidor]

Sorry,

I am using the NI9219.

[nyc_(is_out_of_here)]

Are you within the current limits of the NI 9219?

Are you connected to terminals 4 and 6 on channels 1,2,3 or 4?

[mcidor]

My limits are -0.025 A to 0.025 A, the standard limits.

channel 1 is measuring V => terminals 4 and 5 are connected

channel 2 is measuring A => terminals 3 and 5 are connected

channel 3 is measuring A => terminals 3 and 5 are connected

channel 4 is measuring 4-wire Resistance => terminals 3,4,5 and 6 are connected. 

The channels are not measuring at the same time. They follow this cycle:

1st :   I perform a V measurement on channel 1

2nd :  I perform a Ohm measurement on channel 4

3rd :   I perform an A measurement on channel 2

4th:    I perform an A measurement on channel 3

[mcidor]

My limits are -0.025 A to 0.025 A, the standard limits.

channel 1 is measuring V => terminals 4 and 5 are connected

channel 2 is measuring A => terminals 3 and 5 are connected

channel 3 is measuring A => terminals 3 and 5 are connected

channel 4 is measuring 4-wire Resistance => terminals 3,4,5 and 6 are connected. 

The channels are not measuring at the same time. They follow this cycle:

1st :   I perform a V measurement on channel 1

2nd :  I perform a Ohm measurement on channel 4

3rd :   I perform an A measurement on channel 2

4th:    I perform an A measurement on channel 3

[nyc_(is_out_of_here)]

http://www.ni.com/pdf/manuals/374473e.pdf   Operating Instructions

[mcidor]

In the conversion time table I can read

Current, ±25 mA

High speed       10.8

60Hz rejection   1.9

50Hz rejection   1.9

High resolution  1.0

I think the times are in seconds...but high speed 10.8 ...

Thank you for your help.

[nyc_(is_out_of_here)]

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@mcidor wrote:

In the conversion time table I can read

Current, ±25 mA

High speed       10.8

60Hz rejection   1.9

50Hz rejection   1.9

High resolution  1.0

I think the times are in seconds...but high speed 10.8 ...

Thank you for your help.

---

Reading current is a relatively straightforward proposition.

Have you tried using a shunt resistor and another DMM to verfiy your set-up?

Why do you thinnk it is taking 2 seconds start making a current measurement?