Measuring resistance in a capacitive circuit

I am using niDMM_Read to get a resistance measurement for a resistive/capacitive circuit. However I need a prolonged time during which the current is passed into the circuit before the resistance is measured. This is to account for the capacitor's charging-time. In other words is there any option where the "niDMM_Read" function can execute for a prolonged time (say 10 secs) before returning with the resistance value? I had another question about the NIDMM soft front panel. Does it use the same drivers as does the Measurement Studio - v3.0.1 - for Visual Basic? How does the soft-panel inject the current? Does it fire several current injections(and take measurements) in a second? If it does, then what is the time duration (milli
seconds) for which the current is injected?

This is really a hardware question. This forum focuses on Measurement Studio for VB questions. You will have much better results posting this question to the Digital Multimeters and Dataloggers section of Developer's Exchange at: http://exchange.ni.com/servlet/ProcessRequest?RHIVEID=101&RPAGEID=8&RFORMNUMBER=2&RHIDETAG=TRUE&UCATEGORY_0=_35&UCATEGORY_S=0.
Best Regards,
Chris Matthews
National Instruments

Similar Messages

Can i measure resistance with a PCI-MIO-16X-10

good day!
In my work we measure inflator resistance with an external ohmeter and switch selector, for now we're working in update this method of measure resistance. The program used to activate the inflators was built in labview 7.0 and use a GPIB and PCI-MIO-16X-10 boards only.
The question is if we can measure resistance with this board (PCI-MIO-16X-10), we can do it?
thanks for all...

Cordero,
Not directly but with some auxiliary circuit elements you can. To measure a resistance you need to know both the voltage and current associated with the resistor.
One way you can do this with a DAQ device is to create a voltage divider using a known external resistor. By measuring the voltage drops across both the known and unknown resistances, you can calculate the value of the unknown resistance. You can use the analog output or the board power supply as excitation voltage for the voltage divider. Use two analog input channels to measure the voltages across the resistors. As long as the values of the resistors are much lower than the input resistance of the analog input channels, you can get good results. The accuracy is limited by how well you know the value of the "known" resistor, the resistance of the inputs, and the accuracy of the A/D converter. The accuracy of the known resistor is probably the largest contributor to the overall error.
Lynn

I am measuring resistance changes using hp 4284A LCR meter. I want to monitor the changes continuously by drawing a graph.Can I?

I am measuring resistance changes in chip using hp 4284A LCR meter. The LCR meter is connected to the PC through IEEE488. I am using Labview 6.1 and window 2000. I want to monitor the resistance changes continuously and get a XY graph about it (the X-axis should be time as a unit of second). It should be also saved as an excel file. Please help me to do this work. I appreciate any help.

You might consider a chart, instead of an X-Y graph. You don't need to supply an x-axis array, if your samples are evenly spaced in time.
A chart gradually (or rapidly) moves from right to left, with new values appearing on the right, and old values disappearing off the left side.
This sort of thing is what LabVIEW was designed for. What specifically, are you having trouble with?
Steve Bird
Culverson Software - Elegant software that is a pleasure to use.
Culverson.com
Blog for (mostly LabVIEW) programmers: Tips And Tricks

PCI-4472 -- Measuring Resistance

Is it possible to measure resistance with a PCI-4472 DAQ card? When I use the DAQMX create measurement channel.vi and set it to resistance measurement I get a error message saying 'this physical channel cannont measure resistance, please select voltage....'

The PCI-4472 is a DSA (Dynamic Signal Analyzer) variety of DAQ board. This means it is optimized for measuring dynamic signals and accurately measuring the frequency components. To measure resistance you will provide a current as gwd mentions, and read back the voltage. You will need to take at least 2 measurements (a requirement of the DSA design).
From the voltage measurement you can scale using Ohms Law (R=V/I) to determine resistance.
Regards,
Jennifer O.

Measuring resistance using 6221

Hi guys, i want to measure the resistance between 2 points using my 6221 DAQ card.
I've searched through the example finder and i found 3 examples on resistance measurement. Now, since i only need to measure on a single instance value thus i tried using the first one (Acq Resistance Sample.vi).
However, in this vi it does not state how do i connect the points to my DAQ. Naturally 1 end would be to the physical channel that i've defined in the vi. For the other end i've tried using AGnd but it doesn't seem to work. I tried this vi using a resistor with a known value but i always get an incorrect value of -1k ohm.
Secondly, which do i select for the Resistance configuration section for this vi? Am i suppose to build a simple circuit before i can start measuring my desired resistance? And i can't use internal excitation source as it prompts an error saying that my DAQ card does not have an internal excitation source.
How do i proceed from here?

This is the incorrect forum for this post. Please see the same post here in the correct forum.
Regards,
Ima
Applications Engineer
National Instruments
LabVIEW Introduction Course - Six Hours
Getting Started with NI-DAQmx

Using measurement studio with my own circuit

Im a computer engineering student
I have designed a circuit which do analog-digital convertor and the computer reads the digital value from the parallel port, and Im looking for an application
I found this nice topic in your site : Measurement Studio Analog Output -- Waveform Generation in Visual Basic
http://zone.ni.com/devzone/conceptd.nsf/webmain/9C9F9227D165EF6C8625687E006CEFF5
and I hope that I can do it for my project
my question is : can I use the parallel port of the PC instead of National Instruments data acquisition (DAQ) hardware in the measurement studio 6.0 ??
thank you alot .
Bader

Hello,
It sounds like your question is really if you can access the parallel port from your Measurement Studio Environment. The answer is yes, and one way to do this is using NI-VISA. In general, I imagine you will be performing viOpen, viRead, and viClose operations on your parallel port. The following discussion forum links should help you get more well rounded on the idea: (note: many of these forum posts have helpful links as well!)
1. http://forums.ni.com/ni/board/message?board.id=170&message.id=25066&requireLogin=False
2. http://forums.ni.com/ni/board/message?board.id=170&message.id=109253&requireLogin=False
3. http://forums.ni.com/ni/board/message?board.id=170&message.id=112975&requireLogin=False
4. http://forums.ni.com/ni/board/message?board.id=170&message.id=96478&requireLogin=False
5. http://forums.ni.com/ni/board/message?board.id=170&message.id=118167#M118167
6. http://forums.ni.com/ni/board/message?board.id=170&message.id=86769#M86769
Repost if you have further questions!
Best Regards,
JLS
Best,
JLS
Sixclear

Measure resistance for long time

Hi, I'm trying to measure the changing of resistance by using this program (picture 14). and I did use "Write to measurement file" which is not what I want. is that any good method to record the data?
I'm using LabView 8.5 + PXI 4072
Attachments:
Picture 14.png ‏83 KB

Open and Write to Text file.
Otherwise you'll have to give us more details of what you want if Write to measurement file is not what you want.
How fast do you want ot read it? Write now your loop is running as fast as it can with no pacing. The only thing controlling the speed is the time it takes the subVI's to execute. If you run this for a long time, you are going to wind up with huge data files.

Why would a PXI 4071 measuring resistance countinue to increase the measured valued for each measurement?

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 KB

Uninitialized 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,
Paul
Paul Falkenstein
Coleman Technologies Inc.
CLA, CPI, AIA-Vision
Labview 4.0- 2013, RT, Vision, FPGA

Using current probe in capacitive circuit

HI
I am required to measure the current flow during charge and discharge of a capacitor with respect to t.
I have initially carried out a transient analysis and selected the I to be displayed however its not very clear and my tutor informed me its recommened to use the current probe, however there are settings associated with it which im not very familiar with.
I have tried to use the current probe i have connected the output to an oscilliscope, seems to be working however i need to know the current flowing once 50% of the Vc is dropped I also need to find time taken for the Vc to fall by 50% so i somehow need to view the current and voltage on a same graph so I can determine once Vc has fallen by 50% the respective circuit current at this time.
I also need to view circuit current after 3CR, so if there is a method of implementing time into the current probe so i can view current at a respective time.
Appreciate any help!
thank you

Hi Hass,
We can add the Measurement Probe to the Capacitor.
Run the simulation, we can find the current information dispalyed in the box next to the probe1.
To have a better view of time, we can use the Transient analysis. In the Transient analysis output tab, choose I(C1) as the only output then you will see the current starts from -3mA to 0.
Regards,
Chen_T
National Instruments

Measuring resistance, changing excitation current

Hi, I am using a cDAQ-9172 and some 9219 modules to measure several resistances. The problem I have is that the resistances aren't entirely electrically isolated from each other, and I suspect the excitation current from measuring one resistance affects the value I record on another. For this reason I would like to sequentially switch off the excitation current on all but the channel which I'm measuring. (e.g. excite channel 1, record resistance, switch off excitation, excite channel 2, record resistance, switch off excitation and so on). Frankly I'm a little baffled on where to start with this. Until now I've been using the DAQ Assistant to set everything up, but I don't think I can achieve what I want with this, so I'm going to have to delve more deeply into communicating with the DAQ. Has anyone got any suggestions on where to start and where I can find some guides on changing the programming of the DAQ sub vi's?
Cheers

I'm getting somewhere with this, configuring one channel to read resistance and all the others to read voltage does work, but I can't get it to change which one is set to resistance. I modified the DAQ Assistant Express VI to accept channel inputs, and then I've set up for loops to generate channel numbers (of the form cDAQ1Modxaiy). The modified DAQ Assistant accepts these numbers and carries out the measurement, but then for subsequent iterations of the for loop, instead of accepting the new channel numbers it just carries out the same measurements on the same channels. Is there some way to force the DAQ to reset the channel allocations between iterations of the loop? I've attached VIs of the scanner VI and the modified DAQ assistant.
Cheers
Attachments:
Self sensing experimental-scanner2.vi ‏28 KB
TimsDAQ.vi ‏81 KB

Power supply spark...fried mobo?

Hey my frieed with a K8N Neo is having a problem..everything was working fine in his pc for 11 months...one day his powersupply sparked and the computer would not boot. No lights, no fans, nothing.
So he set in a replacement for a power supply and recived a new one. After plugging in everything the computer would still do nothing, no lights fans etc. Do you think the motherboard is fried? I've checked all the jumpers and they are fine.
His specs are:
Athlon 64 3200
MSI K8N Platinum
X-Infinity case
512 Geil Ram
Thermaltake 420W purepower (W0009R)
120 GB Hard drive
Thanks

Gildan,
You asked the following:
btw, how do u do (4)? (which was how to read voltages on motherboard with voltage multimeter (VMM).
Fiirst thing to do is to read and understand following thoroughly:
VMM USAGE INFORMATION
Many troubleshooting procedures require that you measure voltage and resistance. You take these measurements by using a handheld Digital Multi-Meter (DMM). The meter can be an analog device (using an actual meter) or a digital-readout device. The DMM has a pair of wires called test leads or probes. The test leads make the connections so that you can take readings. Depending on the meter's setting, the probes measure electrical resistance, direct-current (DC) voltage, or alternating-current (AC) voltage.
Usually, each system-unit measurement setting has several ranges of operation. DC voltage, for example, usually can be read in several scales, to a maximum of 200 millivolts (mv), 2v, 20v, 200v, and 1,000v. Because computers use both +5 and +12v for various operations, you should use the 20v maximum scale for making your measurements. Making these measurements on the 200mv or 2v scale could "peg the meter" and possibly damage it because the voltage would be much higher than expected. Using the 200v or 1,000v scale works, but the readings at 5v and 12v are so small in proportion to the maximum that accuracy is low.
If you are taking a measurement and are unsure of the actual voltage, start at the highest scale and work your way down. Most of the better meters have autoranging capability: The meter automatically selects the best range for any measurement. This type of meter is much easier to operate. You just set the meter to the type of reading you want, such as DC volts, and attach the probes to the signal source. The meter selects the correct voltage range and displays the value. Because of their design, these types of meters always have a digital display rather than a meter needle.
CAUTION: Whenever using a multimeter to test any voltage that could potentially be 110v or above, always use one hand to do the testing, not two. Either clip one lead to one of the sources and probe with the other, or hold both leads in one hand.
If you are holding a lead in each hand and accidentally slip, you can very easily become a circuit, allowing power to conduct or flow through you. When the power is flowing from arm to arm, the path of the current is directly across the heart. Hearts have a tendency to quit working when subjected to high voltages. They're funny that way.
I prefer the small digital meters; you can buy them for only slightly more than the analog style, and they're extremely accurate, as well as much safer for digital circuits. Some of these meters are not much bigger than a cassette tape; they fit in a shirt pocket. Radio Shack sells a good unit (made for Radio Shack by Beckman) in the $25 price range; the meter is a half-inch thick, weighs 3 1/2 ounces, and is digital and autoranging as well. This type of meter works well for most, if not all, PC troubleshooting and test uses.
CAUTION: You should be aware that many analog meters can be dangerous to digital circuits. These meters use a 9v battery to power the meter for resistance measurements. If you use this type of meter to measure resistance on some digital circuits, you can damage the electronics, because you essentially are injecting 9v into the circuit. The digital meters universally run on 3 to 5v or less.
Now that you have a nice shiny DIGITAL VMM make sure that you read its manual to understand out it works. Practice taking reading on household batteires and the likes first. Once you are confident and have confirmed that you have the proper lead in the neg/pos connector of your multimeter you are now ready to take some reading from your motherboard. Remember to always ground yourself first to dissipate static electricity, Put the black lead sensor against the case and then use the red lead sensor to carefully probe various points on your motherboard. Be very careful to only touch one point (soldering point, chipset leg, or a motherboard trace) at a time. You want to absolutely avoid short circuiting two such points. As long as you only touch one single point at a time you will be safe and get good reading were voltage is present. I usually use a gator clip connector to affix the black lead to the case, leaving me one hand for flashlight or magnifying glass and other to handle red VMM lead.
Here is how to get a Vddr reading on a MS-7025 Neo2 platinum: http://xtremesystems.org/forums/showthread.php?p=583463
(Put red lead sensor on green dot)
Here is how to get a Vcore reading on a MS-7025 Neo2 platinum: http://www.xtremesystems.org/forums/attachment.php?attachmentid=23902&stc=1
Your Board layout may be slightly different but just keep looking for something similar near your RAM and CPU. Remember to always use only the red lead sensor while being extremely careful to only touch only one spot at a time.
Have fun,

Using cFP-AI-110 to measure rpm:capacitance in the card?

I am attempting to measure the rpm of a number of different augers. The augers have a magnet on them that closes a magnetic switch when the magnet passes the switch. I have built a circuit with a very small amount of power traveling through a resistor and measure the voltage across the resistor. The magnetic switches are in series with voltmeters. I have attached a picture.
The idea was that by measuring the time between closed circuits, I could calculate the frequency of the augers. When I use multimeters, the simple circuit I built works perfectly; a closed switch will cause a meter to read (say) 9v, an open circuit reads 0. However, when I swap in the analog input card for the multimeters I encounter a problem. When the circuit is closed MAX instantly shows the proper voltage, but when it becomes open the voltage decays slowly. In other words I get a triangle shaped waveform, and since some of the augers spin rather quickly the peak to trough distance is almost non-existent.
Does anyone know why the voltage is measured properly as soon as I close the circuit, but why it decays slowly once it is opened? This problem only occurs if I use the NI card.
Thanks for your time
Attachments:
rpmcircuit.jpg ‏9 KB

If the drawing is right, a pull up seems more reasonable to me
You don't want floating inputs at your cFP.
If the contact opens, the - input floats and need to be pulled to to + input to measure 0V
Greetings from Germany
Henrik
LV since v3.1
“ground” is a convenient fantasy
'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'

Resistance measurement using PCI-6602

Hello,
I would like to measure the resistance between 2 points using my PCI-6602 counter/timer card while using LabVIEW. The resistance values to be measured will vary between 10 ohms and 1000 ohms approximately.
I found three examples in LabVIEW example finder for measuring resistance but am not sure which one to use. Moreover, which pins of the PCI-6602 would be used for measuring the resistance?
Please advise me how I could use this PCI-6602 card for measuring resistance values and what the pin configuration would be.
Thank you,
Viktoriya.

As you have written, the PCI-6602 is a counter/timer board. It has no analog input and is not suited for analog measurements !

Keithley 2010 resistance measurement via LabVeiw 8.5

Hello!
I have Keithley 2010 multimeter and I want to measure resistance with it under LabVeiw 8.5. I download needed configs from official web-site. It almost works, however there is one problem. After each resistance measurement multimeter switch to the voltage mode. It's look like: resistance measurement ->voltage mode ->resistance mode->resistance measurement ->voltage mode->resistance mode->... So it mesuare once per second or less. It's not enough fast for me, I need something about 10 times per second. Could you please help me?
Thanks in advance!
Sergey
P.S. http://forums.ni.com/t5/LabVIEW/Fast-readings-with-Keithley-2010-Multimeter/m-p/91867 - doesn't help

I received this answer on Keithley forum:
*RST
ENSE:FUNC 'RES'
ENSE:RES:RANGE 10
ENSE:RES:NPLC 0.01
ENSE:RES:AVERTATE OFF
For I = 1 to 100
:READ?
Now read the unit with a VISA READ
Next I
So I used SCIP commands via VISA WRITEs, and it helped me.
Best regards and thanks,
Sergey

Ni 9218 and temperature or resistance measurement

I'm looking for advise on ways that the NI 9218 could be used to measure resistance from an RTD that will operate in the 100 to 140 Ohm range. I understand that a channel of the 9218 can be configured to measure current (+/- 20 mA). So I would think that it might be possible to setup a configuration to measure the resistance indirectly by converting the measured current to resistance using V=IR. Is this reasonable and possible?

Thanks for your help and the link. I'm thinking of using an Omega RTD possibly a SA1-RTD
http://www.omega.com/pptst/SA1-RTD.html
But I could work with a different RTD if need be. The SA1-RTD gives 100 ohms at 32 degrees F which would be the lowest temperature (and resistance) that I would need to measure. Maybe I could put a fixed resistor in series with the RTD and get the resistance level a bit higher and use less current.
I'm trying to avoid the addtion of another module to the system that Im working with and I do have a single channel available for a temperature measuement on the 9218.

Measuring resistance in a capacitive circuit

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