Setting Input Resistance on the PXI-4071
The specifications for the PXI-4071 DMM indicate that the input resistance can be chosen as either 10 MOhm or 10 GOhm for the 100 mV, 1 V, and 10 V ranges. I see where this can be input on the instrument soft panel, but I have been unable to locate how to configure the input resistance when using the DMM in a VI. Suggestions?
Thanks!
Jeff
Jeffrey Zola
Solved!
Go to Solution.
You need to use a property node.
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Attachments:
input resistance.png 13 KB
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I'm struggling to measure the uA or low mA level of current from my micro power source by means of FP-AI-110. However, current values produced with less than 100 ohm of the external load applied is not correct since it is influenced by the module's input impedance (100 ohm, according to its circuitry given via the instruction manual), I guess. I tried to connect much smaller resistor like 1 ohm in parallel to reduce total input impedance but it appeared not to work out. Is there any way to resolve this or these kinds of a module (FP-AI-100, 100) is not just proper for measuring small currents?
Thanks for reading.If the internal resistance of the load is small compare to the input resistance of the DAQ (100 Ohm), the load resistance will have most of the current flowing through it and the measurement will not be accurate. Attached is a drawing that will explain a little more what is happening.
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Why is it so hard to find the ranges for the PXI-4071??????? I called National and they told me:
The ranges that are possible to use are:
+-.02
+-.20
+-2
+-25
+-250
Yet when I open the soft front panel there is a range up to 1000 volts. Where is this listed?? I need ranges for VDC, current dc and resistance ( opens...infinite) I'm using the DMM drivers that ships w LV 8.6.
ThanksAll of the range specifications will be found in the PXI-4071 user guide and specifications document.
If you search on ni.com for 4071 you will find the PXI-4071 product page. Going to the specifications tab, and then clicking "detailed specifications" opens this document. It contains all of the specifications and accuracy ratings of the device.
NI 4071 Specifications (Multilingual)
Page two specifies that for DC voltage the following are valid ranges:
100mV
1V
10V
100V
1000V
which also show up in the DMM soft front panel.
For DC current, see page 4, which states
1uA
10uA
100uA
1mA
10mA
100mA
1A
3A
Resistance, page 5,
100Ohm
1kOhm
10k
100k
1M
10M
30M
100M
5G
Thse pages also have the charts for the accuracy of the DMM at each one of these ratings.
Eric S.
AE Specialist | Global Support
National Instruments -
I have a PXI-4071 DMM and I am measuring a connection in the UUT. The value should be around 0.3 ohms. The program (exe) will run aprox. 20 times and during these 20 runs the measured value will progressively increase until is is over the limit of 1.5 ohms. If I shut down the exe and run the VI as a standalone (continuous loop), the resistance will gradually come down to 0.3 ohms. I then close LabView and restart my exe and the readings are normal (0.3) but then continue to increase until they are over 1.5 ohms. This process has been repeatable for the last week. I have attached the code I am running. What could be the problem with the DMM code?
Attachments:
DMM_MeasResistance2.vi 64 KBUninitialized shift registers are a good thing to check for such a problem. Do you see the same response with a soft panel and your DMM? if not then it is in code. Uninitialized shift registers would start at 0 (default is usually 0) and will retain their values from run to run. Just a possibility dont have LV up right now so I cant check the code sorry,
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Paul Falkenstein
Coleman Technologies Inc.
CLA, CPI, AIA-Vision
Labview 4.0- 2013, RT, Vision, FPGA -
Setting up the sample rate on a PXI-4071
I am new to this and hoping that some one can help...
I have a DC power supply connected to a PXI-4071 that I am attempting to get some stable DC voltage measurements using LabView but
the measeurement values are all over the board so I am guessing that I am missing some sort of sample rate set up.
Any suggestions?
Thanks
Attachments:
My VoltageRead.vi 30 KBI figured it out..
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Why is the PXI-2575 not recommended for 2-wire resistance measurements?
The spec for the NI PXI/PXIe-2575 says "Note The NI PXI/PXIe-25-75 is not recommended for 2-wire resistance measurements". Why is this? If I want to perform 2-wire resistance measurements, what would be a good alternative?
It really depends on your measurement. The problem with 2-wire resistance measurements is that the resistance of the wiring and the switch path will be included in your measurement. If you are measuring in the kOhms to MOhms, this should be neglible. But measuring anything smaller will add a large error. That is why 4-wire resistance measurements are recommended. The sense lines can measure the voltage across the part you actually want to measure and an accurate measurement can be made.
This is true for all switches.
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ChrisDuplicate post: http://forums.ni.com/ni/board/message?board.id=270&message.id=4840&jump=true
Applications Engineering
National Instruments -
Hi,
I am using NI LabVIEW, NI PXI 4071, and NI PXI 6070E to measure current through a variable resistance. Now, I am using one channel from SCB-68, but I want to add another channel in parallel so that I can have two resistors instead of one that I cam measure current through them.
I have attached a Pdf file showing the setup for hardware in use and LabVIEW code also.
Can anyone look at these files and give me guide lines or ideas that can help me resolving this issue, please.
Thanks in advance.
Best Regards,
Shaheen.
Solved!
Go to Solution.
Attachments:
IV copy for HS.vi 55 KB
Layout of NI Cards.pdf 248 KBYour 4071 can only do one measurement at a time. Your DAQ cannot measure resistance either nor has it got any analogue inputs.
However, you could use a multiplexer and multiplex your 4071 DMM. This wont give you simultaneous measurements but can acquire data one after the other, the speed is obviously dependent on the multiplexer you choose!
Hope this helps.
Beginner? Try LabVIEW Basics
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Hi all,
I have spent some time piecing together a system and I'd like a sanity check before pulling the trigger on this purchase. The system will contain the following hardware:
1. Chassis: PXIe-1078
2. Controller: PXIe-PCIe8361
3. 3 x PXIe-6363 (16 analog inputs each card, 32 digital inputs each card, all internally clocked @ 10kHz)
4. 2 x PXI-6224 (32 digital inputs on one, 8 digital inputs on the other, externally clocked in "bursts" of 62.5khz)
5. Labview software
The three PXI-6363 cards will be responsible for a mix of analog and digital measurements made @ 10 kHz, timed continuously by the onboard clock.
One PXI-6224 will be clocked externally @ 62.5 kHz and will be used to collect digital data on a 32-bit port. These clock pulses will not be continuous, but will occur in bursts lasting for 2ms every 20ms.
The other PXI-6224 will be clocked externally @ 62.5kHz as well and will be used to collect digital data on an 8-bit port. These clock pulses will not be continuous, but will occur in bursts lasting for 2 ms at random intervals.
My questions are:
1. Am I planning anything that looks unreasonable for this hardware?
2. Should I expect issues with data transfer rates with the PXIe-PCIe8361? I will be operating well within the advertised 110MB/s throughput of the device. I plan to stream this method... NI Fast TDMS data streaming
3. I have only ever used NI cards for continuous measurements made by an onboard clock. When I set up a task to collect data that is externally-timed, will the DAQ be expecting a "continuous" clock pulse, or will the system wait patiently for clock pulses to arrive at any rate (any rate within the spec of the card, of course)?
Thanks, any input is appreciated.Hello LucasH0011
1-As long as you put the PXI-6224 and the PXIe-6363 cards in the corresponding slots, meaning the express(PXIe-6363) in the express and the hybrid(PXI-6224) in the hybrid.
2-I think you would not have issues with the transfer rate.
3-Your timing specifications sound reasonable to me, I think you will be fine.
Here is a document that has useful concepts for the use of cards:
http://www.ni.com/white-paper/3615/en/
It is for the M-Series, but the concepts apply to the X-Series as well.
Regards
Ernesto -
We use 4110 voltage source for current measurements on pxi-4071. We supply high-ohm (1.5 GigaOhm) resistor with few volts and measure current on 4071. All cables are shielded on ground of 4110 voltage source, but cables are about 5 meters long. What can be reason for constant current 5 nA at zero supply voltage? We don't know whether it software or hardware problem, and i already asked this question in LabView forum, autozero enabled in max doesn't help. Could be a reason bad shielding of ground in pxi-4110 voltage source
I would focus on the hardware side initially. I would try the following steps.
1) Make a current measurement on the 4071 with the inputs open to see if there is an offset. If so we should look into the DMM configuration.
2) Connect your cabling and/or resistor without the 4110. If this adds the offset then it seems to be shielding/noise related.
3) Connect the cabling and/or resistor to the 4110 with the output disabled. If this adds the offset then it could be ground related or also related to an offset in the 4110 output.
Steve B -
Pxi-4071 aux I/O how to output a control signal?
HI, I am working on Pxi-4071 dmm card. I want to use aux I/O to out put a control signal for a relay on/off. Technically, I want to know how to do it with labview. Is any examples to start?
Thanks
LimingHello Liming,
The DMM is capable of sending TTL triggers out on both the PXI_Trig lines and on the AUX connector on the front connection. These signals are intended for controlling National Instruments switch modules and not powering/closing third party relays.
If you're looking to control a National Instruments Switch there are example programs that demonstrate synchronous scanning with DMMs and Switches. To locate these examples open LabVIEW and go to Help» Find Exampled... Then Navigate to Hardware Input and Output» Modular Instruments» NI-Switch (Switches).
If this isn't what you're looking to do, or if you have additional questions, please feel free to post back with more information.
Have a great weekend!
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Measure Power using Labview and two PXI-4071 DMMs
Hello,
I am trying to make a simple VI. I am measuring input AC voltage and Current using two PXI-4071 DMMs. I want to Calculate Power and Power Factor. I am able to read the voltage and current fine. I just dont know how to calculate the power and power factor. Im looking for real power not watt*amps. Please Help.
Scott
Attached is my VI
Attachments:
Measure AC Voltage and Current.vi 42 KBScott,
It appears that another applications engineer (Sean_N) has been assigned your initial forum post. I assure you that he is working on finding an answer to your question. We would like for our customers to limit questions to one forum so that we do not duplicate efforts on our end. I will contact Sean to remind him that you are awaiting a response. I will also point all future traffic from this post to your initial one.
Thanks,
Kareem W.
National Instruments
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