Diferancial measurment in ELVIS II

Help please!
I send 30 mV voltage to AI channel, then I create task with this parameters:
input terminal configuration -Differential mode.
maximum value - 0,1 V
minimum value - -0,1 V
When DAQ reads channels, value of AI is 45 mV.
When I change ranges to (-1;1), value of AI is 32 mV(it becomes more correctly). I cant understand why ?.

Hello Manushak,
You mentioned that you are generating a very low voltage (30mV) from the VPS and see a sample-rate dependency on your results. Since the VPS cannot reliably output that low, I assume you are using a voltage divider to drop the VPS output to 30 mV. If so, what is the resistance of your divider? The analog inputs on NI ELVIS are multiplexed to a single ADC. If you are measuring more than one channel in a task, it sequentially switches between them and there is some settling delay proportional to the source impedance. For a description of this behavior, see the section titled, "Multichannel Scanning Considerations" in the NI ELVIS II manual: http://www.ni.com/pdf/manuals/374629c.pdf
If this is your situation, you could decrease the impedance of your divider, measure slower, or measure just one channel in your task. If that's not practical for some reason, you could use a unity-gain buffer on the output of your divider.
I hope this is helpful.
Charles

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Frequency measurement for ELVIS

I am using Elvis and I want to measure the frequency of an analog input signal.
I am using this program I found in a manual form NI.
I am using LABVIEW 8.0.
The problem is that the program is not reading the frequency.No mather the frequency I try to read it always reads r=the same thing.
I have attacheted the program below.
Solved!
Go to Solution.
Attachments:
masurarea frecventei.vi ‏22 KB

Americanu22,
A couple things you'll want to consider:
1. To ensure frequency information is correct you need to be sampling at 2*[Highest Frequency in Your Signal].
2. You may want to consider a continious acquisition with a setup like this(This example can be found in Help»Example Finder under Hardware Input and Output»DAQmx»Analog Measurements) :
Good Luck!
Regards,
Dustin D

Measure current and voltage in Elvis and labview

Hi! We're setting up a control system setup for class where we need to monitor the current and voltage that we are supplying/drawing from the ELVIS hardware within a LABVIEW setup. So far, we can accurately display voltage input and outputs from the AI and DAO terminals respectively. However, we can't seem to find a direct way measure current draw. I believe that we are supposed to be able to get DMM readings from the AI5 channel, but either we're not doing it correctly, or we still need to place a known resistance across it (which we cannot do, due to variable loads). Any advise please?
Cheers,
Gerald

Are you using Elvis I or II? From your post, I will assume it is Elvis I but please correct me if this is not the case. Page 38 of the manual shows that ACH5 is used for capacitor or diode measurements for the DMM. To measure current, use the connectors on the front of the Elvis unit and then route the current HI/LO on the protoboard to either the oscilloscope or an analog input channel. You can use the DMM Soft Front Panel to monitor current as well.
Message Edited by h_baker on 07-09-2009 04:54 PM
Regards,
h_baker
National Instruments
Applications Engineer
Digital Multimeter Resources

Does anyone know how to use ELVIS in Labview to get current and voltage measurements?

Trying to use ELVIS in Labview to get measurements with a NI myDAQ.

I have changed from using the ELVISmx driver as I was unable to call on the digital multimeter of the myDAQ twice, I have set up a VI using the DAQ assistant with the myDAQ, I am using the AI0 port for a voltage reading and using the DMM for my current reading, the circuit is working as I am measuring the voltage on a resistor after the ammeter but I am unable to get a current reading in order for it to work. If I have something wired wrong please let me know, thank you. My circuit is a 12VAC power supply, going through a potentiometer to drop the voltage to 8VAC, which passes through a resistor, ammeter is in series after this and attached to another resistor to complete my loop, the AI0 for my volt meter is connected across the second resistor, I have the proper voltage reading when I run the VI, but am unable to get a current input. Thanks for the help.
Attachments:
Mikes Project2.vi ‏131 KB

RPM measurement using NI ELVIS? help me out

i want to measure RPM from two different sources simultaneously using NI ELVIS and i am using an hall effect sensor, how to do it?
info:
my hall effect sensor has 3 pins Vcc, GND, out
i connected the Vcc, GND to ELVIS board itself and the OUT pin to CTR0- SOURCE pin (is this connection correct? i left CTR0-GATE and CTR0-OUT free)
from one of the website i found that i need to use frequency counter
so i went to NI-DAQmx->create task->acquire signal->counter input->frequency (i did a test run, nothing was working)
then i did edge count NI-DAQmx->create task->acquire signal->counter input->edge count, here i could see the up counting every time i passed a ferrous material in front the sensor.

I'll pass this to you to see if it helps
http://zone.ni.com/reference/en-XX/help/370466W-01/mxdevconsid/elviscountsigconn/

Why can't I find ELVIS || in Measurement & Automation Explorer

Hello!
My PC has installed LabVIEW2010,NI-DAQmx9.6 and NI-ELVISmx4.2.3.When it connects to ELVIS || hardware, I can't find ELVIS || in Measurement & Automation Explorer,but can find In PC device manager.What's the problem?

(I try to have this thread move to the right place.)
LabVIEW Champion . Do more with less code and in less time .

How do I use elvis to record data from a pasco rotary motion sensor

I want to use a pasco rotary motion sensor (a rotary encoder) with ELVIS to record angular velocity. I have a LabPro system which I could also interface. But I was hoping to keep the hardware less complicated by wiring the sensor directly to ELVIS. Does anyone have a sample .vi which would record sensor output?

Hi PCM,
Measuring the time between pulses can be a little complicated. You can have a look at this knowledge base to get an idea of how it can be accomplished. However, since the sensor's output is a stream of digital pulses you can use the counters in this card to get some information from the digital signal. You can use one of the counter’s inputs in the NI-ELVIS and get the frequency or period of the digital signal. One good point to get started is by looking at the counters examples built in LabVIEW, you can find them going to Help > Find Examples > Hardware Input and Output > DAQmx > Counter Measurements. I hope this is helpful.
Ana P
National Instruments
Applications Engineer

HPE 1420b Measurement Problems

I have an HPE 1420B freq/cntr board. I can read frequencies using the hpe1420b_stand_meas()
NI driver calls (CVI 5.0), HOWEVER, for low frequency signals I get time-out
errors.
It is not symetrical across channels (occurs near 150 HZ on inp2 but low
frequency ~3Hz works on inp1). I'm using the same code for both channels.
What it appears NOT TO BE:
* an aperature problem
* trigger level problem
* signal amplitude
* AC vs DC coupling
* a board problem (2 boards show same effect)

Hello
pinnacle1406,
I was
wondering if you could clarify some of the information about this problem:
1. When you
say the measurements are incorrect, what do you mean? I have attached a circuit
diagram below. What are the values when measured at point 1 (across both
resistors), point 2 (across 3.3k ohm resistor) and point 3 (across 4.7k ohm
resistor)?
2. You said
you tried the measurement on about 6 different NI ELVIS’s, are the measurements
consistent on each station?
3. How are
you measuring the current with the NI ELVIS? Are you using the Digital
Multimeter Express VI in LabVIEW? Are you using the NI ELVIS Instrument
Launcher?
4. What DAQ
card are you using to take measurements from your NI ELVIS?
5. Are you
using the proper null correction to lower the noise error?
From the NI
ELVIS Suite data sheet, the current specifications are given as:
DC accuracy ........................................
0.25% ±3 mA2
2Proper
null correction at the common-mode voltage can reduce ±3 mA error to 200 μA
noise.
Even with
proper null correction, your current may be too small for the NI ELVIS to
measure. If you are just trying to demonstrate the current dissipated in a
simple circuit, I would recommend changing the resistor values so that you have
a larger current running through your circuit.
I hope this
information is helpful. Please let me know if you have any additional
questions.
Message Edited by Matt A on 01-18-2007 07:30 PM
Message Edited by Matt A on 01-18-2007 07:30 PM
Message Edited by Matt A on 01-18-2007 07:31 PM
Matt Anderson
Hardware Services Marketing Manager
National Instruments
Attachments:
circuit.GIF ‏3 KB

Calculate measure in parent child hierarchy

Halo everyone
I have a requirement about parent child hierarchy namely:
1. see the following picture as a sample.
the situation I got here is every employee has its own measure (Sales Amount). when it rolls up to 'Employee1' so the Sales will calculate all measure (Employee1 and all the descendents) but when it drill down, 'Employee1' will ONLY show its own 'measure' (it does'nt calculate from its descendents).
Any suggestion, Any idea, Any sharing, Any inspiration would be appreciated. thanks alot.

Hi Vin,
We can use Descendants() funcion, which returns the set of descendants of a member at a specified level or distance, optionally including or excluding descendants in other levels.
Please refer to the document below:
http://msdn.microsoft.com/en-us/library/ms146075.aspx
Regards,
Elvis Long
TechNet Community Support

How to use IMPEDANCE ANALYZER to measure input $ output impedance of BJT circuit

Am currently doing experiments by using NI ELVIS IMPEDANCE ANALYZER but am now suffering a problem on how I can connect it so as to measure input and output impedance of a BJT circuit.
My circuit is as shown in my attachment.
Attachments:
ni.docx ‏46 KB

I see that you already posted on another thread. Please refer to it here:
http://forums.ni.com/t5/Instrument-Control-GPIB-Serial/HOW-TO-USE-ELVIS-IMPEDANCE-ANALYZER-TO-MEASUR...
Regards,
Nathan S.
Applications Engineer
National Instruments

NI Elvis Read Current and Voltage Simultaneously

Greetings,
I'm trying to read voltage and current on an NI Elvis II to characterize the output of a TENS unit (currently using SignalExpress).
What I have worked out:
Thanks to advice on another question I asked earlier today, I've now got the timing worked out so that I can produce log data at 10kHz when measuring voltage through the CH1 Scope input.
I'm now moving on to the other have, and am trying to add current in as another task. It makes sense to me to try and read that through the DMM current input. However, I'm getting errors that will only allow me to read the value once, instead of at the 10kHz rate I measure the voltage at (and would prefer that they are read in sync).
This seems like it should be pretty straightforward to do, but I'm just not seeing it. It's really important (in a non-academic and non-job way) that I get this done tonight, and I really appreciate all the support this board has offered. If there's anything I need to provide to make the issue clearer, please do not hesitate to post.!
Would it be easier to run this through LV proper instead of SignalExpress?

The DMM that is onboard the NI ELVIS II is not specced to run at the rates you're requesting. In fact, the DMM is a software timed device, which means that it will only collect samples when your computer tells it to. I created a quick benchmarking code to see how many measurements that an ELVIS II could take per second and I came up with about 4 or 5. You can recreate the code yourself to see similar results.
After one second, the elapsed time Express VI will output a 'true' which will stop the while loop. The DMM will be constantly acquiring and writing data into an array. When the while loop has finished, an array of DMM data will be output. The size of this array will indicate the number of samples that can be read in one second.
Nathan M.
Applications Engineer
National Instruments

MDX query runs on SQL but does not populate 'Measures' in Powerpivot

I ran MDX query on SQL 2012 for looking the products and their shipping status
The code is given below:
WITH
set Date1 AS
strtomember( "[Time].[2014].[Q4].[2014-Jun].[" +format(now()-2, "MM") + "/"+format(now()-2, "dd") + "/" +format(now()-2, "yyyy") + "]")
set Item1 as
{ [Item].[ItemID].ALLMEMBERS}
SELECT NON EMPTY { [Measures].[Shipped Qty], [Measures].[Shipped Amt], [Measures].[Ordered Qty], [Measures].[Ordered Amt] }
ON COLUMNS,
Date1*[Item1] ON ROWS FROM [ABCD]
WHERE (
[Channel].&[OL],
[Geography].&[A.9])
The query gives desired output when run in SQL. But when I run the same query in while pulling data in PowerPivot, Dimensions i.e. Date and Item are populated but measures were not populated. Can anyone please help me understand how to populated Measures
in PowerPivot?

Hi apoorv,
It was hard to reproduce this issue on my test environment. I would suggest you try to use a simple MDX query to check if it will retrun the correct measures data. Please see the screenshot below:
In addition, you can also create a SQL Server Analysis Services trace to capture some events for furhter investigation.
Use SQL Server Profiler to Monitor Analysis Services:http://technet.microsoft.com/en-us/library/ms174946.aspx
Hope this helps.
Elvis Long
TechNet Community Support

I want to measure rpm using 100 ppr incremental encoder via digital input

i want to measure rpm using 100 ppr incremental encoder via digital input max speed (4000 rpm)
am using 9178 c-DAQ chassis and 9426 digital input module
pl provide me example code for this

Hi asaccullo.
The recommended settings for encoders are using the counters in the daq cards. Using digital I/O’s is not recommended, the encoders send digital signals but one of the main differences between using digital IO vs counters is that counters are designed to handle these type of events.
Here I found several examples in ni.com/code that you might check:
Imitation Quadrature Encoder with DAQmx Counter Tasks
Use Counter Frequency to obtain an Encoder Rotational Speed
An Elvis is a daq device, so this should work for you.
I also found an example for myDAQ, it uses the DIO but with a counter task in the set up.
Regards,
steve.bm
AE | NI

ELVIS 1 AND ELVIS II LABVIEW VIs COMPATIBILITY

I am currently working on a project that was previously using Labview (8.5.1) vis built for elvis I, we have now moved on to Elvis II and are experiencing problems that are believed to be steming from the differences in channel configurations. Could some one be as kind to avail channel configurations for both elvis I and Elvis II and what modifications we may need.

Hi,
First, I want to reference you to the support page for the NI ELVIS II and its help manual.
NI ELVIS II
http://sine.ni.com/psp/app/doc/p/id/psp-458/lang/en
NI ELVISmx Help
http://digital.ni.com/manuals.nsf/websearch/825085B4A34566818625745F006DF0F8
I want to verify what exactly is going on in your program when you upgraded to NI ELVIS II. Are there any errors you are seeing? Are you able to get it working in Measurement and Automation Explorer? Also, what drivers are you currently using?
Regards,
Jordan F
National Instruments

For our ELVIS II units, I receive error message -200220. What is wrong with these units when they worked a month ago?

On several computer stations, we receive the error message -200220 when selecting any instrument on the Instrument Launcher when the Run option is pressed. This message has not been cleared after the computer was rebooted and the Box power cycled. What is wrong?
I can not find this error code in the product documentation.
Solved!
Go to Solution.
Attachments:
Elvis_Error_Message[1].docx ‏464 KB

From the screenshot you attached, it looks like there is no device specified on the front panel, which means that the error you see is correct, the device identifier is invalid. Are there any available devices populated in the Device control? Does your ELVIS II show up as connected in Measurement and Automation Explorer (MAX)?
Donovan

Diferancial measurment in ELVIS II

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