What should be the hardware for measuring relay parameters using LabVIEW and PXI?

[42113]

I am an undergraduate student working on project for measurement of automotive relay parameter measurement using LabVIEW. The parameters to be measured are:
1)Operating time 2)Release time 3)Pull up voltage 4)Drop off voltage 5)Coil Resistance 6)mV drop across contacts.

For this, I am using NI PXI 1052, SCXI 1125 and SCXI 1313 attenuator with LabVIEW.The relay to be tested is of 12V-15A.

I want to know what extra electronic circuitry will be required to measure the above parameters?


Message Edited by 42113 on 03-10-2008 08:05 AM

[mallorim]

Hi 42113,

In order to make suggestions about any external circuitry you might need, I will need to know more information. I am not a part of the automotive industry and afraid I am unfamiliar with the parameters you listed. If you could elaborate on each of the parameters, it would help.

However, just from the list, parameters 3, 4, and 6 appear the be simple voltages which you shouldn't have a problem with. I believe that the only way you will be able to measure coil resistance is if you know that current passing through the coil and then measure voltage drop across it. Post-processing could then be used to divide the recorded voltages by the known current to get resistance. Resistance Measurement - Indirect Method is a good document that discusses ways NI can measure resistance.

Hope this informaiton helps, Mallori M.

[42113]

Hello mallorim,
Here, I am just briefing the parameters mentioned above: 

1. Pull-up voltage:  A relay is said to 'pull-up^' when it changes from the un-energized position to the energized position. The voltage present at the time of pull-up is called pull-up voltage.
2. Drop-off voltage: A relay drops off when it moves from the energized position to the un-energized position. The voltage present at the time of drop-off is called drop-off voltage.
3. Operating time: With a relay de-energized and in its initial condition, the time which elapse between the application of a characteristic quantity and the instant when the relay operates is called operating time.
4. Release time: With a relay energized, the time which elapses between the removal of a characteristic quantity and the instant when the relay stops operating is called release time.
5. Coil resistance: The resistance offered by the coil when the relay is energized is called coil resistance.

[mallorim]

Hi 42113,

Thanks for explaining the parameters you will be measuring. So I guess to summarize, you will be characterizing a switch’s specifications. In order to do this, you will need some sort of Data Acquisition card to use in conjunction with the SCXI-1125 Isolation Amplifier you mentioned in your first post. The 1125 was created to amplify small voltages so that the resolution and 10 V range of most DAQ cards could be better made use of. The 1125 therefore passes voltages through with no acquisition being performed. If you do not already have a DAQ card available, I would suggest looking at PXI DAQ cards to easily fit in your PXI-1052 chassis and that are capable of both analog input and output. When considering a card you will also want to make sure it is capable of the time resolution you want when measuring Operating and Release times and the voltage resolution . Are you using an embedded controller in your PXI-1052 chassis, or are you communicating with the chassis with MXI cabling kit?

With regards to whether or not you will need other external circuitry, the better question to ask yourself is how are you planning to measure these parameters? After you have an idea or procedure then you can look to see if your hardware is capable of these measurements.

For instance, for the pull-up and drop-off voltage measurements, I imagine this might be done with some sort of a voltage sweep. Then you would want to use the synchronized analog input and output of the DAQ card. You would therefore need access to the analog output lines with a terminal block or a breakout box.

I hope this explanation helps. Regards, Mallori M.