Solenoid Plunger Response Time

[drkidd22]

Hello,

I have to measure the response time from the plunger in a linear solenoid. The instrument I have available are a oscilloscope and current prove. The solenoid is 12VDC. Is there a way that I can determine when the plunger fully opens and closes using the scope, or do I need some other type of instrument to do this/.?

 

[ronsimpson]

You probably should use a push button switch that the plunger pushes against.
The solenoids I use are for AC current. I noticed the current is different when out verses in. Using the current probe you might be able to monitor the current. In my case the current is low then in and higher when out.
I hope you are using a digital storage scope. It will make thing much better than an analog scope where the picture will disappear.
good luck

 

[alec_t]

Make sure the solenoid coil has a spike suppression diode connected across it then just try applying 12V across the coil for at least the duration of the plunger travel and monitoring the voltage across the coil with the scope. If the (ferro-magnetic) plunger is moving through the coil it generates a voltage which adds to or subtracts fom the 12V so the movement should (with a bit of luck!) be detectable from the scope trace. At least, in theory. Let us know the result.

 

[ronsimpson]

Is this a real project or for school?

 

[Reloadron]

A little more information as to the solenoid would help. Like the stroke and force? Do you have a data sheet on the solenoid? There are ways to do what you want to do but I am having a hard time picturing exactly what you have. Also how accurately do you want to measure the time?

Ron

 

[drkidd22]

This is a real project. The thing is that the plunger is not externally exposed. It's more like a valve for fluid line.
See the link below to a datasheet of a solenoid valve similar to the one I have.

Solenoid Valve .pdf

 

[Reloadron]

OK, new game now. What you have is a pneumatic solenoid valve with a 12 VDC coil. The link you provided for valves similar to your shows a typical response time less than 30 mSec. Not to say yours will meet or exceed that specification. Something that you can try is using the scope trigger off the coil voltage the instant the coil is energized then see if there is a glitch in the voltage when the solenoid reaches full stroke opening the valve. Another option as was mentioned would be to look at the current on the scope. Look for a perturbation in the current when the solenoid reaches full stroke. Measuring this is not going to be real simple.

There are other ways of doing this using an accelerometer but they get complicated and expensive.

Ron

 

[drkidd22]

Ok, I think it can also be done with an acoustic sensor. I think I have one that hooks up to the oscilloscope. I will try looking for the perturbations in the current using the current scope prove and will also take some readings with the acoustic prove and see what I get.

 

[Reloadron]

What I was getting at with the accelerometer was using it as an acoustic sensor to look at the "bang" of the solenoid. You apply a voltage to the coil, that voltage triggers the scope, you look at the "bang". Something along those lines.

Ron

 

[jamie_s]

yes you can measure using a scope, put an 0.1 ohm resistor on the low side and measure the voltage across it with the scope, when the solenoid opens, you will see a change in the waveform, this is how we also test opening times for fuel injectors
**broken link removed**

 

[BrownOut]

This is a real project. The thing is that the plunger is not externally exposed. It's more like a valve for fluid line.
See the link below to a datasheet of a solenoid valve similar to the one I have.

**broken link removed**

I like it, but I would spend some time characterizing the test while validating the results with a different method first, even if it means tearing one of the units up to attach some other sensor. You don't want to fool yourself into thinking some artifact is the real indicator.

 

[drkidd22]

I used both the current probe method and the acoustic prove. Both provided similar results. Only that with the current prove I could not see the "glitch" when the valve closed, it was noticeable on the voltage signal dough. It was easy to see when the plunger started to travel using the acoustic prove, but a little more difficult when it was closing (i think this was due to the spring rate).

 

[Reloadron]

OK, then that is a good thing. Both methods apparently gave similar results and if they were repeatable then it would seem you are into something.

Ron