10-06-2014 08:33 AM
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.
10-06-2014 09:23 AM
cDAQ 9181 is just a chassis with one open slot.
Which C-series module are you using?
10-06-2014 09:28 AM
Sorry,
I am using the NI9219.
10-06-2014 09:49 AM
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?
10-06-2014 10:18 AM
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
10-06-2014 10:18 AM
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
10-06-2014 10:29 AM
http://www.ni.com/pdf/manuals/374473e.pdf Operating Instructions
10-07-2014 01:17 AM
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.
10-07-2014 07:43 AM
@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?