Acquire generated signal with this hardware ?

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Hello everyone,

I didn't really know where to post this, I apologize if it's the wrong place.

I'm very new to the LabView thing, and I have for project to trigger an injector and so to create a digital signal like this:

Due to the characteristics of the signal (110V, 10-20A, injection duration: ~20ms), someone recommended me this hardware (sorry if I'm not allowed to post these links):

- programmable power supply: http://fr.farnell.com/ea-elektro-automatik/ea-ps-9200-25-2u/alimentation-1-voie-200v-25a-prog/dp/242...

- USB interface: http://fr.farnell.com/ea-elektro-automatik/usb-interface-ea-if-u1/interface-for-psi-el-usb/dp/126814...

I'll try to figure out on how I create (on my own for now) the signal with LabView.

My question is, will I be able to acquire the generated signal with this hardware in LabView, do I need something else ?

Thanks.

[Dennis_Knutson]

You should really post to the instrument control board for this type of question.

I have not looked at the specs of the instrument but the second link you posted said that the instrument cd comes with aLabVIEW driver. See http://www.ni.com/downloads/instrument-drivers/ on what a driver is and how to use one.

Look at the instrument specs to see how fast It will accept commands. The performance it's something you should be asking of the vendor. Send them that waveform image.

Your mention of acquire makes no sense. You can only generate a voltage with the instrument.

[Henrik_Volkers]

Your powersupply is as far as I understand the spec, far to slow. I would look for a power amplifier. Just by your picture I would look for a bandwidth of 100kHz. However you need to know the bandwidth of your signal.  (And if you want to apply predistortion to compensate mechanical effects and other nonlinearities multiply your amplifier bandwidth by 3 to 10 😉

Contact the manufactor of the power supply/amplifier and send them some signals plots with specs you want to create.

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Thank you for your answers.

I thought that maybe retrieving the signal was possible. So a sensor and an USB NI 600x  would work ? I don't want an expensive solution, just display the signal.

For the power supply, I need to trigger one injection per second or even 2/3 secondes. And the coil of the injector has a time constant (correct term ?) of 5 ms. That's all I have.

I don't need to recreate the exact same signal in term of frequency.

[Henrik_Volkers]

Please explain again what you want:

Build a setup to create what?

Timing specs?

Measure (and display) what?  (Output current :), but how do want to measure it? Shunt? Hallsensor? Monitoring output voltage(?) of the supply/amplifier?

Needed accuracy? time resolution?

The 600? have poor input impedances, and sometimes pure software timed outputs...   depending on what you need and what you willing to add, yes maybe a cheap 600X can do the job.

However, spending 1.8k for the powersupply and  ~200 to make the measurements..... mh ....

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I want to trigger an injector, with one injection/second for now, maybe 2 or 3 eventually, but not more. The injection duration is ~20 ms (pull-up time ~5ms + hold time ~15ms).

And I need to visualize the output current, and display that through LabView. So a solution to measure it, mainly for the duration of the 2 phases, with a precision of one ms. How ? I don't know, the easiest solution. If you have some suggestions...

Thank you for your time, sorry, this is really not my "area".

[johnsold]

I have designed and built injector drivers. To get a waveform somewhat like the one you showed requires a sophisticated and fast control circuit. I would not call that a digital signal.  It may be controlled by some kind of logic signals, but that is an analog signal.  No programmable power supply I have seen is fast enough to come close.

The pull-in current does not typically go into a ring/overshoot flat-topped waveform as you have shown. It follows an exponential curve defined by the L/R rise time and the current limit set by the supply voltage and the injector coil resistance. For the injectors I have seen that current limit is much higher than the current required to generate the magnetic field required to open the valve.  That oscillatory response could be the result of a switch-mode current regulator.

Similarly, the hold-in current does not occur by magic. Either the supply voltage needs to be changed (open loop system) or the current sensed and regulated (closed loop system).  The kind of ringing you show can occur in a switch-mode current regulator.

Lynn

[empty_]

Let's just say I want a waveform like that (pull-up and hold durations aside).

Thank you Lynn.

[AndrewPolk]

If you are looking for an NI solution to drive a solenoid or piezo injector, the NI 9751 cRIO module should do the trick.  The module has built-in boost voltage circuitry (up to 190V) and has the capability to use an external power supply if needed (with a 5 ms high-voltage phase duration, I would recommend an external power supply).  The module does have built-in current sense capabilities for solenoid injectors, but is not intended to be used for every injection.  We typically use a differential voltage probe and current probes in conjunction with a fast, simultaneously sampled AI (NI 9222, NI 9223) to continuously monitor injection events.  Good luck and feel free to send me a PM if you have any questions.

[johnsold]

It is pretty hard to tell much from a photo of a scope screen.

The top trace looks like a switched voltage, but certainly not the current in an inductor. The middle trace timing seems to match the lower trace but not the upper trace. The first peak of the lower trace looks like the current in an inductive load when a switched voltage is applied, but to switch the current off almost instantaneously the way that trace drops requires very high voltages and power which do not appear. 

So, I am not sure how to interpret those traces. What does each of them represent?

Lynn