Dc motor measurements

Dear ppl.
Need help to traduce oscilloscope voltage readings, to Torque, Angular speed and Back-emf from attached circuit.
Motor is a 550 watts hand-driller.
A-F mutual inductance, shaft inertia and friction are unknown and set by default.
The other parameters show its actual values.
Should I convert volts to Nm, rads x seconds and Volts directly?
Are those values logicals or outrageous?
Thanks a lot.
Solved!
Go to Solution.
Attachments:
550 watts hand driller sim.ms12 ‏70 KB

Hello danielsoy
The first thing you need to find is the relation voltage (or current) with Torque. It think there´s is an ecuation that relates current and Torque. Then, knowing the torque and the shatf inertia you can yield the angular aceleration of the wheels. Doing some numeric integration you can calculate the angular speed of the wheels. That´s the way you can approach the problem. With an encoder it would be much easier, cause you can measure angular position, speed and acceleration and with the acceleration you can yield the torque.
Hopefully this information will help you.
Omar R.
Applications Engineer

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I have no experience with measuring high AC voltages but rather with measuring AC current. As mentioned by others, usually current transducers are used which usually have output voltages of 1, 5 or 10V for full range. Even many clamp-on amp meters have an analog output.
When measuring AC voltages it should be no problem to use a transformer for galvanic isolation. In any case, for such high voltages there should be a sensor or at least a "front end" of the DAQ system which is complety isolated. I once designed a system for measuring up to 500VDC and we used a completely isolated ADC front-end, with isolated DC-DC converter supply and isolated data lines.

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Hi!,
I am trying to configure a Fieldpoint system to measure the following (its for a DC motor test station):
Motor Voltage: 0-240 VDC
Motor Current: 0-50 ADC
Generator Voltage and Current: same as for motor
Options which come to my mind are:
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2) Convert both voltages and current into 4-20mA and use only FP-AI-111
My questions:
1) Which is a smarter config?
2) Would there be any issues of isolation that I need to consider?
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B
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OS is Win200
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Gurdas
Gurdas Singh
PhD. Candidate | Civil Engineering | NCSU.edu

Hello Gurdas,
You could use the FP-AI-110 to measure both your voltage and current signals. However, you will need to create an attenuation circuit so that you can measure your signal in the 0-10VDC range as you have described. You can also use a current shunt resistor to measure the current by running the current through this resistor and then measure the voltage across it. You will most likely need a resistor near 0.01Ohms that can handle up to 50A. (50^2*0.01)= 25W. That is a big resistor.
It would still be best to convert both to voltages since the modules measure voltage. Even the FP-AI-111 uses current shunts and measures a voltage.
Another thing to know about taking motor measurements is Flyback voltages generated from the coils. These v
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Regards,
Bill B
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What sensor should be used to measure speed of motor

Hi,
I am using NI PCI-6624 to control the speed of dc motor. I have used "PWM-Counter Output.vi" example to generate PWM pulses to control the input power of motor. I am using "counter output" and "analog input" terminals of PCI-6624. Counter output terminal is used to generate PWM signal and "analog input" terminal will be used as an input from speed sensor.
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Ayaz,
the straight forward low-cost solution for velocity measurements is using a quadrature encoder. With your DAQ device you could use the second counter of the board to measure the frequency of one phase, but that's jus one option amongst others.
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Hi,
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Hi everybody,
I was just born in this Labview world and I´m quite lost. I´ll explain my situation:
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Solved!
Go to Solution.

Times to wait BEFORE a measurement is started is something you have to do manually since it's up to the user.
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I want to run a step motor and take pressure measurements at steps of 2mm

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Sanjoy,
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I don't see anything wrong with your approach; however, I'll throw out a few thoughts:
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Attachments:
Meas Dig Period-Buffered-Continuous-Low Freq 1 Ctr_Angular speed from encoder.vi ‏72 KB

Hi Suksun,
Only had a quick glance at your code, but can you drop the samples to read to 100.
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How to measure current on DC servo motor.

Need to measure current on DC servo motor. What is the best way to measure the current on the motor as it moves to position? Using PXI-7344 controller and MID-7654 drive unit.

This is not an easy task. Here are some ideas:
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Measuring servo motor current

hello;
I am trying to measure servo motor's current. But i could not find a way to do this. I use a 7344 motion control card. and Labview 6.1. If it is availible with this equipment it will be helpful.
I am waiting for your messages.
thanks.

mekanikzombi,
I assume you're referring to the current of the voltage output of the motor drive? We have no built in utilities to measure current output, but you could measure it easily enough with a DMM. Let me know if I assumed incorrectly, thank you.
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Hi all,
I've been grinding my head for days on this problem.
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Attachments:
APS_linear1_5_stable.vi ‏137 KB
8_17_11_25s_1800Hz_150_2.txt ‏977 KB

Hello Ruben_D
I'm sorry this is causing you an inconvenience! Can you please provide a link to the EPOS2 install file as I seem to be missing a number of their dependent VIs. Thank you very much!
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What is it you need to characterize? For what purpose? Using an external sampling clock can help make the test run much more quickly, but is not absolutely necessary.
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Billstrong,
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How to measure torque of servo motor

Dear Experts,
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Torque specifications should be available from the motor manufacturer. I'm not aware of a standard way to measure torque vs. speed, but maybe a google search would turn something up. Here's what I found.
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Dc motor measurements

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