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TB 4300, Connected to PXIe 4300, Measurement issues

June 2, 2017, 11:44 am
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Hi all,

 

I am trying to measure voltages using the cards mentioned above. This card has 8 channels and I am connecting them to a battery pack all connected in series. The issue I am having is that the first and last channels, channel 0 and 7 are reading low (approx 2V whereas they should be measuring 4.05 V). The other channels are all reading properly. I am sure that this must be a grounding issue but after many attempts of re configuring the grounding cables in different ways, the results are the same.

 

When using only 4 channels, ie channel 0 to 3, everything measure properly, it is only when I have all 8 channels attached that problems occur.

 

Any help is appreciated.

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Tricking NI 9219 with External Excitation

June 5, 2017, 10:16 am
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Hi all,

 

I need to take force measurements using full bridge load cells, but the ones I have need 10 Vdc and 5-15 Vdc excitation.

 

I know that the NI 9219 doesn't support external excitation, but I wonder if I could "trick" the board by selecting internal excitation and then connecting the ex. wires to another differential voltage supply. Assuming that I don't have grounding or voltage stabilization problems and I scale the measurements correctly, would it be any issues?

 

Regards,

 

Geancarlos Zamora.

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6009 voltage reading jumping around

June 5, 2017, 7:31 pm
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I am using an NI-6009 to read and send to a Hastings mass flow controller.

 

I have the output for the MFC going to ao0 and the input from the MFC going to ai2.  Here is the problem:

I am getting voltages that jump like this:

 

-1.434

-1.045

-1.678

-.991

 

But if I take the ground and signal from the MFC and hook them up to a voltmeter, I get voltages like this:

 

2.313

2.309

2.316

2.308

 

These voltages are very stable when read with the voltmeter, but when I put the exact same inputs to the usb 6009 I see jumping.  What is going on??

 

Thanks

 

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Problem with NI 9227

June 5, 2017, 9:12 pm
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I had purchased NI 9227 for current measurement. But is there any possibility to measure the current of 4-20mA range from a temperature transmitter by using NI9227, since NI 9227 have a minimum measurement range of 5A. 

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9220 in 9064

June 5, 2017, 10:14 pm
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Can two NI-9220 modules with all channels sampled at 100 kS/s be used in cRIO-9064?

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error 200877 when trying to change the sample rate

June 6, 2017, 4:16 am
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hi everyone,

i am not sure if this is the right forum. i develop a c++ program that should be able to change the sampleRate for a USB-6210. when i do this, i get a -200877 error (see attachment).

while the message explains a lot, a cannot solve the problem doing this:

DAQmxErrChk(DAQmxCfgSampClkTiming(getHandle(), nullptr, sampleRate, DAQmx_Val_Rising, DAQmx_Val_ContSamps, getDeviceConfig()->getScanBlockSize()));
uInt32 val = getDeviceConfig()->getScanBlockSize() * 125;DAQmxErrChk(DAQmxSetBufInputBufSize(getHandle(), val));

what am i missing?

thank you!

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9421 with Rotary Encoder

June 6, 2017, 6:31 am
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Hello,

I'm trying to use a rotary encoder (AEDT-9810 Z00) with a 9421 to provide feedback for a stepper motor in LabVIEW. The datasheet for the encoder says that the maximum voltage it can use is 7V. However, the 9421 manual says that the minimum voltage needed for a channel to turn "on" is 11V. I was hoping to use DAQmx for position of the encoder. I also have a USB-6001, but it apparently doesn't support the encoder functions of DAQmx. I'm not quite sure where to start if I can't use the 9421.

Thanks,

Carl

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USB 6225 - Ghosting issue

June 6, 2017, 11:45 am
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Hello all,

I've begun using the NI 6225 DAQ (USB) a couple of weeks ago, and noticed some peculiar ghosting issues.

I'm using my DAQ to measure roughly 50 single ended analog signals.

I'm attempting this through Labview, using the DAQ assistant. All my inputs are configured as NRSE (non referenced single ended).

 

 

Scenario 1:

I measure 8 analog inputs. One input is connected to a low impedance 5V source and the others are open circuited. The result is that I see 5V across all inputs. This sort of ghosting makes sense because the DAQ's internal capacitor in the analog input circuitry does not have a discharge path. 

Even if I remove the 5V source, I still see 5V across all inputs. This still makes sense because there is no discharge path.

 

The inputs are

AI 0 (AI 0+) --connected to 5V

AI 1 (AI 1+) --open circuit

 

...

AI 7 (AI 7+) --open circuit

 

Scenario 2:

Measuring 9 analog inputs. One of them is connected to a low impedance 5V source and the others are open circuited. The result is that I see 5V across all inputs. HOWEVER this time around, if I remove the 5V source, the inputs all read 0V.

 

The inputs are

AI 0 (AI 0+) --connected to 5V

AI 1 (AI 1+) --open circuit

 ...

AI 7 (AI 7+) --open circuit

AI 8 (AI 0- ) -- Notice that this channel is the negative differential input for differential measurements.

 

Does anyone understand what is going on with the DAQs internal circuitry that would make AI 8 alter the measurements in such a way?

 

Aside:

In my completed application, most channels will not be left open circuited. But it is a possible scenario, 

so I intend measure a grounded dummy signal after every 'real' measurment, to discharge the capacitor.

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How to connect a rosette strain gage to the NI 9237?

June 6, 2017, 1:21 pm
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Hello!

 

I have done strain measurements with two and four actives srain gages using the  NI 9944, but I still don't know how to connect the terminals with a rectangular rosette strain gage.

And other question is If I could use a single grid strain gage just with NI 9944 accessory or do I need another accessory?

 

I would really apreciatte your answers!

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Sample Rate is slower than expected

June 7, 2017, 8:14 am
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Hi

I am trying to sample the temperature off of RTDs using a NI 9226 module with a cDAQ 9184. The module should support about 50 Hz if you use 8 channels according to its manual. It seems like the cDAQ should also be able to support this frequency, but Im not 100% sure. Currently when I run my vi file I only get a new temperature reading once every 2 seconds.  I cant tell if this is due to my code or if I misread something and one of the devices cant handle the frequency that I am asking it to do. If I run only one channel the it is at about 10Hz, which I also find odd since it should be able to work much faster than that. Thank you for the help

NI model datasheet http://www.ni.com/pdf/manuals/376922c_02.pdf

cDAQ datasheet http://www.ni.com/pdf/manuals/372087a.pdf

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PXIe-6341 X-Series - Drive digital output and pulse on the same line

June 7, 2017, 1:31 pm
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Hi,

 

I'm working on an application that requires me to be able to individually drive some digital inputs high and low while performing some measurements on a UUT. This digital channel driving is handled manually; for example, I drive a channel high, perform some actions/measurements on the UUT, and drive the channel low again as needed. However, part of the requirement is now for those same channels to also be pulsed (single pulse high for 50ms for example). I had previously been using a PXI-6509 for these digital operations but then the need came to do some pulsing so I upgraded to the PXIe-6341 which has built in counters. The pulse spec has to be pretty accurate and deterministic so instead of trying a software timing setup I am using this. 

 

My main question is am I able to treat the digital IO lines on the 6341 as both DIO and counter lines? Put another way, am I able to continue manually driving digital lines but then pulse those same digital lines (using a counter reference) or do I have to use separate "counter" output lines for these pulses? I'd rather not have to run another line to the same test point where one is for manual digital operations and the other is merely for pulsing, if that makes sense.

 

If I am able to, how would I setup the channels differently from normal DIO lines?

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Selective retriggerable counter output

June 8, 2017, 9:50 am
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I'm trying to set up a retriggerable digital pulse train generation on PCIe 6321 using ANSI C with the additional feature of selective triggering. I have a counter output task which will generate a fixed pulse train, and be set as retriggerable by a PFI line. There will be an external pulse train being supplied to PFI line. However, I want the counter output task only be triggered by even, odd, or every other fixed number of the triggers, is it possible to achieve that? Thanks.

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Whether MyDaq can be used to interface the eeg cable with labview????

June 8, 2017, 9:22 pm
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I wanted to measure eeg signal and hence I use eeg electrodes but inorder to process it in labview...how can i interface it with labview...whether i can use Mydaq or any other boards????

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Saw-tooth type profile from SCB-68 voltage ports

June 11, 2017, 11:34 pm
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Hi,
 
I have very little experience in LabView.
 
The voltage excitation from SCB-68 seems to be a saw-tooth type profile. Is there any way I can avoid this and get a clean signal? 
 
I am trying to take voltage readings from a Panasonic WM-034B microphone. I am using SCB-68 connected to a PCIe-6353 card. On SCB-68, there are three points that connect to the microphone. 1. Output, 2, Ground & 3. +5V. I am getting a saw-tooth type voltage profile reading even when there is no sound. At first, I though this was a microphone issue. Later, when I connected a wire from the +5V terminal to output terminal in SCB-68, it was showing a slighltly upscaled version of the same saw-tooth profile.
 
I work in controls, and it is possible that the controller may act on this frequency which is not part of this system. It may cause problems down the line. Is there any way I can get a clean signal from the board?
 
Thanking you in advance. I am also attaching the reading from the microphone which resembles a saw-tooth profile.

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This board

June 12, 2017, 12:38 pm
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Hello. Could someone tell me if this board is a NI Daq board?
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NI 9171 and NI 9421: change the sampling rate in Matlab

June 13, 2017, 5:31 am
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Hey, I have a question about changing the sampling clock to acquire digital data in Matlab.

 

I need a counter input channel and a digital input channel for my application, which should be both run in the background. I have no external clock and so I have to use the 100kHz, 20Mhz or 80Mhz time base. The problem is that the maximum sampling rate for the digital input channel can be only 10kHz. I read in the forum some things about using the frequency generator. But the commands to divide the external time bases are not described for Matlab applications. My question:

1.)Is it in general possible to reduce the sampling rate without any external clock or use a clock with a frequency less than 10kHz?

2.) If yes, is it also possible for Matlab applications?

 

My code:

daq.getDevices;                           
                                                 
ni9421_1 = daq.createSession ('ni');  
ni9421_2 = daq.createSession ('ni');  
              
% Add Counter Channel and Clock Connection
ni9421_1.Rate = 100000;
ni9421_2.Rate = 10000;

addCounterInputChannel(ni9421_1,'cDAQ1Mod1','ctr0','EdgeCount');
addClockConnection(ni9421_1,'external','cDAQ1/100kHzTimebase','ScanClock');

addDigitalChannel(ni9421_2,'cDAQ1Mod1','Port0/Line2','InputOnly');
addClockConnection(ni9421_2,'external','cDAQ1/100kHzTimebase','ScanClock');

ni9421_1.IsContinuous = true;
ni9421_2.DurationInSeconds=10;
lh1 = addlistener(ni9421_2,'DataAvailable',@(src, event)savDat1(src, event, fid2));
ni9421_2.startBackground;

 

 

Error code:

NI Error -201002:
Sample Clock Rate must match the frequency of the internal timebase specified as the Sample Clock Source.

To use the specified Sample Clock Rate, set the Sample Clock Source to OnboardClock. To use the specified timebase as the Sample Clock, set the Sample Clock
Rate to the frequency of that timebase.
Sample Rate:  10.0e3
Source Terminal: /cDAQ1/100kHzTimebase

Task Name: _unnamedTask<1F>

Status Code: -201002

 

 

I would be very happy if someone can help me with my problem.

Thank you in advance!

 

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Which Multiplexer to buy?

June 14, 2017, 3:27 am
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Hello,

 

I am currently trying to build a measurement setup to monitor the performance of solar modules.

I already have a Keithley interfaced with Labview that measure the module over time and record the measurements

 

What I would like is to be able to measure 4 cells with a multiplexer and only one Keithley, programming that with LabVIEW (every 15 min, the system would measure Module 1 then Module 2 then Module 3 then Module 4 by switching the multiplexer and then measuring with with the Keithley)

 

I have seen the USB‑6001 Multifunction I/O Device (http://www.ni.com/en-gb/support/model.usb-6001.html) and I was wondering whether it was right for what I want to achive or not. Could anyone help me, please?

 

Thanks,

 

Gabriel

 

 

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Required Suggestion to Begin labview

June 14, 2017, 5:49 am
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Hello All,

 

I need your suggestions to buy a right software, because now i'm in the step1 of labview environment for programming. For the first step i'm planned to buy a hardware Multi function I/O (USB-6001) with a labview base development software. Is it ok to begin? or i need to do any correction in my purchase. Kindly share your views and guide me to the right way.

 

Thanks in Advance

Santhoshkumar

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DAQ Recommendation

June 14, 2017, 8:37 am
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Hello,

My adviser has tasked me with gathering parts to build two new controller boxes for our lab. Currently we have one controller box using two USB-6009s that records and controls 2 mass flow rates, opens and closes 8 valves, and records 2 pressures within the system. Our new control box should also do these tasks, as well as control an additions 4 valves, for a total of 12.

Based on this I believe our new DAQ card should have 2 analog outputs, at least 4 analog inputs, and 12 DI/O. As I understand the USB-6009s are a much older product, and so we would like to purchase something that is more up to date. I'm fairly new to all this so if someone could recommend a product I would greatly appreciate it.

Thanks. 

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Measuring self noise of ADCs

June 15, 2017, 1:34 am
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Hello all

 

Is there any standard procedure with which we can practically measure self noises of NI PXI /non PXI based DAQ (ADC) cards please?

 

Regards

Asim

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