Rpm measurement

Hei! I have a school project on making a steering system on a scale model boat. Now we been working around the clock to get this thing working but there is one problem/challenge left.
So i have a Myrio, hall sensor and a dc motor and im trying to measure the rpm on the motor.
The Hall sensor gives a pulse when the motor turns one round. I have conected the hall sensor to a digital input on MyRio and from there i get a True/False signal for the sensor.
I guess if i measure how many pulses i got in one secund and multiply that by 60, i get the rpm? but im not sure how do to that i labview.
Does anyone have some idea on how to do this? Thanks

PetterMartin wrote:
I did not get that to work so i must find a nother solution.
Maybe something like this (picture) the teori is that the encoder resets every secunds and counts the number of pulses, but its not working.. Any solutions?
What didn't work with the other solution? What isn't working in this?
So lets say you get that counter reading the pulses. Do you know how much time has elapsed between pulses? That is the other half of the equation. You must have a way to read pulses, and know the time that they came in at. Reading with DAQ will give you this. Are you assuming that the loop that this code runs in will iterate once every millisecond? If so then this could be a working solution. Use a single sycle timed loop, on a deterministic OS (myRIO is one) to force it to run at a specified rate.
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Similar Messages

NI 9411 for RPM measurement

I have a Keyence sensor/amplifier system (LV-NH32/LV-N11N) that looks at a rotating disk. I am trying to acquire the RPM of the disk as it spins down. I have National Instruments module NI9411in NI DAQ 9174. I need to make my own LabVIEW VI for my sensor/amplifier system to interact with 9411. I would like someone to tell me how to go about it. I am trying to look into example finder but I am not very sure which examples to look at. My disk starts to spin down at 10,000 rpm.

Hi Tat-LSU,
Here are two piece of example code from the ni web site that have been used for rpm measurement. They could serve as a model for your code.
https://decibel.ni.com/content/docs/DOC-8172
https://decibel.ni.com/content/docs/DOC-13039
These examples are a good place to start. Let me know if you need additional resources.
Regards,
Josh Brown
Applications Engineer
National Instruments

RPM Measurement using Quadrature Encoder and PXI 6602 counter

Hi,
I am on a project at work where I need to verify the speed (in RPM) of an unloaded motor which can operate up to 1400 rpm. After doing some research, i determined that a quadrature encoder could be used to make the measurement. I am looking at this encoder http://sine.ni.com/nips/cds/view/p/lang/en/nid/205321.
I have a PXI 6602 counter/timer module in which I would like to interface to the quadrature encoder. I would like to create a VI that allows me to calculate the speed using the encoder. Can someone provide me with details of what needs to be in the VI or an example which can do this? At the most basic level, i want to calculate the speed on demand. After doing this, i would like to figure out how to quickly calculate the speed so that i can determine response time of the speed changing within sub-millisecond resolution (1 ms resolution max).
Further, i created a VI that allows me to change the pulse width of a 100 Hz pulse train at run-time which tells the motor controller the desired speed. I would like to be able to use this VI to change the speed of the motor and the first VI (that I am seeking help about) to calculate the response time (time between the initial speed and settling at the new setpoint).
I am familiar with the NI example finder, but have not been able to find an example that I can use.
Thanks,
Gary

Hey Gary,
I think for you setup, you should try using the Meas Dig Frequency - Low Freq 1 ctr. You can find it by searching example finder with 'low freq'. This vi tells you the frequency of a digital signal by sampling between two pulses and inverting the time between pulses. If you hook up your encoder to a counter and have that counter specified in the vi, it will be able to give you on demand readings of frequency (you can do some multiplication to get the rpm value, freq*60/pulses per revolution of encoder). A simple way to take continuous readings is to put a while loop around the daqmx read and the data output of the read. You can also replace the numeric indicator to a waveform chart to graphically display the change of frequency or rpm readings over time.
You should be able to integrate this as two separate tasks with the pulse train vi you created earlier.
Hope this helps
Luke W

How to use cfp ctr 502 for rpm measure+cfp configure in labview

i'm new in handling cFP's,i need to measure rpm of an engine using cFP CTR 502.Plz i need detail regarding which method either pulse counting or frequency method is required for my application,Plz also tell me is there any possibility of configuring cfp using labview

Hi,
please see the following link to NI-Discusion forum. There is simaler question.
http://forums.ni.com/ni/board/message?board.id=110&message.id=1764&requireLogin=False
I also send you tow links to LabVIEW examples. I hope it helps.
http://venus.ni.com/stage/we/niepd_web_display.DISPLAY_EPD4?p_answer=&p_guid=BCB1261CBE2635D2E034080020E74861&p_node=174404&p_rank=&p_source=Internal&p_submitted=N
http://venus.ni.com/stage/we/niepd_web_display.display_epd4?p_guid=BCB1261CBE2635D2E034080020E74861&p_node=
TN

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/

How can i compute the time elapsed between two pulses or the period of an encoder signal if I dont have a constant rpm?

I need to compute the rpm of an engine using information from an optical encoder attached to it. the engine is running in transient mode so the encoder pulse doesnt have a constant frequency. I need to get the period betwwen two rising or falling edges using DAQmx.
Any ideas?

Using an M Series or TIO device you can measure the period between two edges (on two different signals) using the two edge separation measurement. I'm assuming that you don't want to use position measurement because the frequency is varying so much? If not, you may be able to set the sample clock period short enough that you get a decent average RPM measurement.
gus....

RPM Measurement without using Counters

I've read several threads on how to measure RPM from optical sensors but they all involve the use of counters on the DAQ terminal board. My issue is that my project involves reading and comparing four seperate RPMs and my DAQ only has 2 counter terminals. Ideally I'd like to just use the analog signal input channels for all four sensors. I've gotten as far as counting the edges of the analog signal using this code snippet.
Solved!
Go to Solution.

nathand wrote:
Sorry, what's the question here? If you can count the edges in an analog signal, you know the number of edges in a rotation, and you know the span of time the analog signal covers (if you don't know this you can simply divide the number of samples by the sampling frequency), isn't that all the information you need to calculate RPM?
If I understand what you are saying, I think that would only work if the RPM were to be constant the run time. I'm trying to make this robust enough to handle varying RPMs and report instantaneous. From what I've read, because my sampling mode here is continuous, my sample rate is 1000 and not the 100 samples per channel.
Attachments:
RPM Measurement.vi ‏22 KB

Creating a digital counter in labview

Currently using a proximity switch connected to an SCC-DIO1 to read pulses from an encoder to develop an RPM measurement ( and angular velocity). How do I convert my digital pulse into a true numeric count per minute (or millisecond)? I'm able to detect the pulse from the module in labVIEW but I'm unclear on how to count the pulses per minute. Currently using labVIEW 7.1.

If all you're doing is counting pulses, you'd actually be better off
using the counters on your DAQ card. They automatically track the
number of pulses and can give other info like frequency. Look in the
Examples for Counter VIs to show you how to use them. There's a pretty
good one named "Getting Started Counter.vi".
If you're set on just using a digital line, the attached image shows
how to setup a basic 32 bit counter. (but I still suggest you have a
look at using the Counters)
Ed
Message Edited by Ed Dickens on 07-14-2005 03:38 PM
Ed Dickens - Certified LabVIEW Architect - DISTek Integration, Inc. - NI Certified Alliance Partner
Using the Abort button to stop your VI is like using a tree to stop your car. It works, but there may be consequences.
Attachments:
32 bit Counter.gif ‏5 KB

Wiring - PXI-6624

Hi All -
I have an application that I need to make use of a counter, we chose the PXI 6624. I'm pretty darn good with the rest of NI hardware, aside from counters FPGA and RF are the only lines I haven't used. I'm running into some trouble understanding how to set up my leads on the 6624 and thought I'd ask on here.
I have a remote optical sensor (Monarch Instruments Model ROS) that I will need to monitor pulses on. Its got 4 leads coming off of it, a common, a signal, a +V excitation(10V), and the cable shielding (ie common). I'm also hooked up to a SCB-100 using their 100 pin flex cable.
The thing that I'm getting hung up on, each counter on the module has 10 pins assigned to it. I keep going through the manual, but I'm having trouble understanding it. Went to NI and the engineer there basically just copied and pasted the same part of the manual that I didn't understand. When asking for more details, about the gate +/- for example the response I got was that "you can if you want to gate the signal you use the gate pins"...I assume that means you can use those pins as a switch to take the signal or not, like you would the Gate on a FET used like a switch. Just an example of how detailed the responses are :-)
Anyhow, I'm reading through and it sounds like each of the inputs almost has multiple functions that overlap, but I'm having trouble digesting it. Can anyone help out with the wiring on this?
Just FYI - Short term, I have 1 sensor that will count RPM as 1 pulse per revolution. We will also want to do direction which will require a second sensor with the two set up much like the quadrature function requires. Only still both will have only 1 pulse per revolution, rather than an encoder with say 120 pulses per rev. Will eventually need to wire up both, but I think if I can figure out just the one I can use that to figure out the rest of the setup on my own :-)
Thanks a bunch!
LV7.1, LV8.5
Solved!
Go to Solution.

External Connections:
Sensor common connected to source - of counter
Signal from sensor connected to source + of counter
Any gate signal you would use for this application would be generated internally using another counter and then internally routed to the gate of the counter that is counting the external pulses. In this case the gate signal would provide an accurate window of time in which to count pulses. An example would be measuring RPM. If you decide to measure pulses for an entire minute, how do you accurately define a minute? If you don't count for exactly a minute, your RPM measurement will be incorrect. Software timing won't work.

Parallel data acquisition problem

Hi everyone!
I’m facing a problem with acquiring data from my NI 6259 BNC card.
What I basically want to do is to measure, let’s say, both RPM of the jet engine as well as temperature. I have thermocouple and of course the voltage of thermocouple is proportional to temp. I also have a phototransistor to measure RPM, but… the signal from phototransistor is non-TTL signal. For measuring RPM I’m using code from: “DAQmx: Counting Non-TTL Pulses with Multifunction Board and Labview”. It is using port redirecting and triggering.
Both measurements are ok when run separately. I mean I can measure continuously temperature and plot it to graph in real time. I can measure PRM with very good accuracy as well. But I can to this only separately, I don’t know how to write a program to measure them both together in one VI.I want to measure (and save to file) both RPM and temperature at the same time.
I think it has something with triggering option in RPM measurements, triggering stops all measurements. Is there any way to measure them both?
Thanks in advance,
Maciek

Hi Maciek,
You are saying it right, there is limitation due the trigger used. The examle you mentioned is elegant for measuring just RPM but adding any other measurement on AI side is nearly impossible since the analog input is triggered depending on RPM value and there is usually requirement on measuring the temperature with fixed sampling period (especially when you want to log it to the file).
I would propose 2 solutions:
The first one is easier and does not require any signal conditioning. It would be just measuring the temperature and RPM through analog inputs (each on one AI channel) and processing would be made using LabVIEW. The sampling rate thus must be made with respect on the RPM signal to be sure that you will acquire enough samples to extract the signal shape (mainly the edges) exactly enough to make the measurement precise and reliable. The temperature will be acquired the same sampling rate so you can select just one of e.g. 100th or average multiple samples into one which will be displayed and stored to a file. There is also one recommendation. Since the USB-6259 BNC card has aggregated AI, it is good to have all AI signals on similar range because switching the signals e.g. 10mV and 10V can cause some accuracy issues. Usually, signal condition before connecting is to the card solves the issue.
Second way how to measure both signals is to convert the signal from RPM to TTL logic, it should not be a problem using one or more transistors. Then it is very easy to measure RPM using only a counter. The temperature measurement will be second separated task, so all will be independently configurable. In my opinion, this is cleaner and more effective how to measure both quantities, but you have to to the converter from your "non-TTL" signal to TTL.
Please let me know if this is acceptable for you, if not, send here the code with deeper comments (mainly about the parameters of the RPM signal).
Best regards,
Martin

Read/acquire signal from remaining empty channels of NI9205 by modifying the vi of ATI Force/Torque Transducer which uses the first 6 channelsof DAQ card.

Hello,
I am using force/torque transducer by ATI Automation. It provides me with its own vi to measure and write the data of the 6 signals (3 axes Forces, 3 axes torques)
Following is my Ni system: -
cDAQ 9172 chassis: Slot 5 - NI 9401, Slot 6 - NI 9205, Slot 8 - NI 9237. (Excitation voltage to the sensor/transducer (0-5V) using 9237).
I connect the 6 signals from the transducer cable to channels ai0,1,2,3,4,5 in NI 9205(differential). The vi uses a calibration 6*6 matrix to finally display the calibrated voltage data.
Now, I wish to use the remaining availabe channels that empty in 9205, namely ai17, ai18, ai19 for other signal measurements.
ai17 channel is connected to Hall sensor that gives out a square waveform corresponding to the rotor rpm. ai18, ai19 is connected to rotor-motor power supply's voltage and current signal respectively.
But I am not able to access these 17, 18,19 channels from ATI company's vi. The vi loads the complete DAQ card (9205), uses only first 6 channels, hence the array data wire consists of only 6 channels. I can split these into 6 individual signals only.
If I use a separate DAQ task to read channels ai17,18,19, then I get the error that this channels are reserved for some other task. Please tell me how can I access all the remaining channels apart from the first 6.
I am attaching the vi here.
Steps to run the "MEASUREMENT main.vi" : -
Load calibration file:- FT8840.cal;
Load DAQ card: NI 9205
Load ctr0 of NI 9401 (I am using this counter for rpm measurement purpose, this is my addition to the actual vi)
Attachments:
DAQ - Copy.zip ‏574 KB

There's nothing I can do to help. I don't have your hardware to be able to modify your code and to set it up to make sure it runs properly. Most people on the forum probably don't either. This is where you'll have to put your programming and LabVIEW skills to work to solve your problem and make it run the way you want to. If you run into a specific problem and get stuck, then please post back.

How to Measure Frequency to RPM NI-DAQmx Tasks

Hello,
I am trying to measure frequency using NI DAQmx task and then convert this to an RPM if at all possible.
I have the following hardware options at my disposal.
I have SCXI 1126 Module along with a SCXI 1327 terminal, as well as a PXI 6289 Multifunction DAQ.
I have wired in a mag sensor to ai7 on my 1126 and when I pass a metallic object I get a amplitude of 6 - 8 so I am able to read the mag sensor.
What I am trying to do is to somehow convert this analog measurement into a RPM while only utilizing the NI DAQmx task.
Any help would be appreciated.
Tim
Solved!
Go to Solution.
Attachments:
Freq Set Up.jpg ‏2993 KB

So I would select new in "Custom Scaling"
Then would I select linear?
Your calculations are simple but I am unsure if this would give me the desired result. From my attachment I am seeing an input amplitude of 6 Hz for each pulse. What I mean by this is that every time I bring a ferrous object near my mag pick up I get a pulse, this is what I was trying to illustrate in the attachment. The analog pulse comes in a 6 Hz so I would simply multiple this pulse by 60 (assuming I get one pulse per rotation) to get RPM?
How would this make sense if I only input one pulse for a long duration of time?
I have notice the amplitude of the pulse input increases with increased pulse frequency. Does this mean the lowest RPM I can record is 360 RPM?
Tim

How to measure current and voltage and rpm with daq device

i am measuring current and voltage and am wondering should i use shunt resistors or current sensors hall effect sensors. i have a pci 6221 and a scc-68 breakout box. what specifications or size should the shunt resistor/current sensor be or should i use another device to measure the currrent and voltage. do i need any other safety device between the resistors, current sensors and the scc-68 breakout box when measuring the current and voltage. will the daq card pci 6221 pick up a signal from the resistor. what terminals should the wires from the resistors and current sensors be connected to in the scc-68. i am using a proximity switch to measure rpm of a motor. should the proximity switch be 2 or 3wire connection. should it have an analog or digital connection and is a power supply required to power the proximity switch and should it have an npn or pnp connection

hello,
i was going to use a 20amp 50mv, or a 20amp 100mv current shunt and connect wires directly into the AI input terminals of the scc-68 from the current shunt would these be suitable. would current shunts such as these be suitable to use http://uk.farnell.com/elc/sh10020/shunt-sh10020-20a-100mv-1-class/dp/1319576 or http://uk.farnell.com/datel/3020-01098-0/shunt-50mv-20a/dp/1339338
is it ok to use either a current shunt or should a hall effect sensor be used such as this http://ie.farnell.com/honeywell-s-c/csla2cd/sensor-hall-effect/dp/1082269 . which of them would be more accurate or are both of them fairly accurate.
when i am measuring voltage can i connect two resistors between the positive and negative of the wires going to the battery and connect two wires from either side of the resistor directly into the analog inputs of the scc-68 and measure the 12-15 volts directly would the pci6221 and scc-68 be able to measure the voltage drop across the resistor.
i wanted to measure rpm also does it matter whether the proximity switch has 2 or 3 wires and should it have an analog or digital/frequency output for cponnecting to the scc-68

Using a 9205 to measure RPM

I have not used labview in over 10 years but now have an application that requires but I am more then rusty. I am trying to measure RPM using a 9205 module and I am sure there is a way to do it. I have a pulsed voltage output from my measurement circuit and so far I am capturing the voltage. Can someone suggest a way to convert these voltage pulses to an RPM value. I am sure some type of leading edge counter would work.
Thanks

Not the cheapest route but there is a SCXI card that measures frquency.
http://sine.ni.com/nips/cds/view/p/lang/en/nid/1661
There may be some other frequency cards this is one I have used in the past. With this card you can create a virtual channel and ask it what frequency the analog signal is going into it. From here there is a conversion from frequency to RPM depending on the type of resolver or hall signal you are using to generate that signal.
This method is the easiest but the cheapest would be to get a cheap AI DAQ device that can measure several times faster than the generated signal (nyquist theorem) then analyze the series of AI reads to determine the frequency. Then convert frequency to RPM. Depending on the signal a USB DAQ device might work, if not a PCI or PXI + MXI card would still probably be cheaper than the SCXI route.
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If 10 out of 10 experts in any field say something is bad, you should probably take their opinion seriously.

What is the correct way to measure RPM using Visual Basic?

I have something that works now, but I want to know if there is a better way. I am using a 6023E, I have a Hall Effect switch that goes low then high each rev when a magnet goes by. I have the signal connected to the GATE pin on counter0. I poll the card for the RPM over and over using code based closely on the example STCsinglePeriodMeasure. While this works, I'm not sure exactly what this code is doing. Do I need to call the entire thing every time? The problem is I need to reset and arm the counter each time before starting the counter, and calling everything was the only way I could get it to work. I'm looking for a way to either trim this down, or maybe there is another way altogether that is more apporpriate. Here's the code:
iDevice% = 1
ulGpctrNum& = ND_COUNTER_0
ulArmed& = ND_YES
ulTCReached& = ND_NO
iYieldON% = 1
iStatus% = GPCTR_Control(iDevice%, ulGpctrNum&, ND_RESET)
iRetVal% = NIDAQErrorHandler(iStatus%, "GPCTR_Control/RESET", iIgnoreWarning%)
iStatus% = GPCTR_Set_Application(iDevice%, ulGpctrNum&, ND_SINGLE_PERIOD_MSR)
iRetVal% = NIDAQErrorHandler(iStatus%, "GPCTR_Set_Application", iIgnoreWarning%)
iStatus% = GPCTR_Change_Parameter(iDevice%, ulGpctrNum&, ND_SOURCE, ND_INTERNAL_100_KHZ)
iRetVal% = NIDAQErrorHandler(iStatus%, "GPCTR_Change_Parameter/SOURCE", iIgnoreWarning%)
iStatus% = GPCTR_Change_Parameter(iDevice%, ulGpctrNum&, ND_GATE, ND_DEFAULT_PFI_LINE)
iRetVal% = NIDAQErrorHandler(iStatus%, "GPCTR_Change_Parameter/GATE", iIgnoreWarning%)
iStatus% = GPCTR_Change_Parameter(iDevice%, ulGpctrNum&, ND_INITIAL_COUNT, ulCount&)
iRetVal% = NIDAQErrorHandler(iStatus%, "GPCTR_Change_Parameter/INITCOUNT", iIgnoreWarning%)
iStatus% = GPCTR_Control(iDevice%, ulGpctrNum&, ND_PROGRAM)
iRetVal% = NIDAQErrorHandler(iStatus%, "GPCTR_Control/PROGRAM", iIgnoreWarning%)
' Loop until 'ulGpctrNum' is no longer armed, or run window is closed.
Do
iStatus% = GPCTR_Watch(iDevice%, ulGpctrNum&, ND_ARMED, ulArmed&)
DoEvents
Loop While ((ulArmed& = ND_YES) And (iStatus% = 0)) And RunWindow.ExitStatus = "Running"
If RunWindow.ExitStatus = "Running" Then
'Run window wasn't closed, so read data.
iRetVal% = NIDAQErrorHandler(iStatus%, "GPCTR_Watch/ARMED", iIgnoreWarning%)
iStatus% = GPCTR_Watch(iDevice%, ulGpctrNum&, ND_COUNT, ulCount&)
iRetVal% = NIDAQErrorHandler(iStatus%, "GPCTR_Watch/COUNT", iIgnoreWarning%)
iStatus% = GPCTR_Watch(iDevice%, ulGpctrNum&, ND_TC_REACHED, ulTCReached&)
If (ulTCReached& = ND_YES) Then
MsgBox "Counter reached terminal count! RPM value may be incorrect"
Else
'ulCount is the period in microseconds, RPM = 1/val*(100000ms/s)*(60s/min)
RPM = 6000000 / ulCount&
' Debug.Print RPM
RunWindow.RPM.Text = Str(RPM)
End If

Finally getting around to this again. My previous post is incorrect, as the code I am using is based on the single period measure (it's right there in the code). I am having a problem with the values returned with this method. Occasionally, the card will return a lower than expected count, resulting in a very large (and incorrect) RPM value. I'm thinking this must have something to do with arming the counter at some unfortunate and coincidental point on the gate signal, resulting in a short count. It must be an unlikely event, because I get thousands of good, consistent values for every one bad one.
To resolve this, I am thinking of going to the single buffered period measurement as suggested above. My idea is to set up a buffer with two values,
and always take the second one (to avoid coincidental arming and short counts). I could also set it up to return more values, and the application could choose the most likely one (ie return three values, throw out the largest and smallest, etc.)
I would rather just use the buffer in continuous mode, since the RPM varies much more slowly than the counter counts, and any snapshot of the buffer at any time would be sufficient, even in the presence of overwriting, etc. This would allow me to arm the counter once and poll it on the fly.
My concern is that in continuous mode, the counter will be throwing a lot of errors which will interefere with the program flow. Can I just set the counter to suppress all errors when I do a buffered read? Worst case, I get a value as it is being written to by the counter, which will have some garbage value (hopefully a recognizable signature) which I can throw out in favor of the other values.
Thanks,
Doug

Rpm measurement

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