Building Peak and Hold output counters: HW and SW required?

[Christ0phe]

Hello,

I am using the 2 counter outputs of USB-6211 and PCI-6602 to drive injectors with PWM commands at rather slow frequencies (up to 10Hz) --- see top picture in the attached file. What I would like to do now is to drive Peak-and-Hold injectors (as shown in the below picture). I wonder if such profiles can be programmed or set in the hardware at the beginning of a test then reset everytime the users want to change the current settings (this latter does not need to be in real-time).

Can I achieve this with my hardware, do I need specific hardware? Is the only solution to build the train of impulsions and send it in a sort of time-based way? I do not really see the SW related that I must use.

Thanks for any insight.
Christophe

[Christ0phe]

Has anyone got ideas?
Thanks,
Christophe

[ThiCop]

Hello Cristophe,

Is there a specific reason why you need to use the combination of the USB and the PCI card?

[Christ0phe]

Hello,

Depending on the number of devices that we must drive we use USB-6211 or PCI-6602. Never the two together.

Thanks to take care of my question.
Christophe

[ThiCop]

Hello,

How accurately should the predefined pattern be followed?

How much deviation of the parameters from there predefined (or set values) is allowed?

[Christ0phe]

0.1% error is allowed. No more. Pattern is shown in the word attached file of the original message.

Thanks.

[ThiCop]

Hello,

If you really need the exact pattern to be completely accurate up to 0.1%, then your pulse parameters should be able to change with maximally a 0.1% error. 

This means that your pulse parameters should be updatable with an error smaller than 1 ms.

Therefore you cannot use Non-Buffered Pulse Train Generation (Implicit timing), because in that case changing your pulse parameters would be done software-timed. This type of Pulse Train Generation can be performed on STC 2 - and STC 3 - chipsets.

Because a computer only has an accurate 1kHz clock available, this would probably not fulfill your needs.

Two other options that could do what you are asking are Buffered Pulse Train Generation (with Implicit Timing) and Buffered Pulse Train Generation (with Sample Clock Timing).These options are only available on STC 3 - chipsets. These chipsets allow you to change your pulse parameters in a hardware-timed manner.

The 6211 card you mentioned is an M-series device and these devices use a STC 2 - chipset. Therefore it will not be possible to do a hardware-timed buffered  pulse train generation.

As far as I know it will not be possible to do the hardware-timed buffered  pulse train generation with the 6602-card.

I don't have one available over here to test it, but of course you can always test it at your side.

The examples to test this can be found the following way:

- Open LabVIEW and go to Help > Find Examples

- Select Browse and go to Hardware Input and Output > DAQmx > Generating Digital Pulses

- Here there should be two examples of the buffered Pulse Train Generation. (starting with "Gen Dig Pulse Train - Buff-... ")

- In the Requirements section they also mention the cards that do support this functionality.

Can you let me know if your test allows you to produce the wanted results?

[Christ0phe]

Hello,

http://decibel.ni.com/content/docs/DOC-12161 --- this shows what I really want to achieve i.e. pre-feed the counter preset with a {duty cycle, frequency} pattern. Unfortunately it does not mention for which hardware the VI is applicable. Are you positively sure that the Vi that is displayed is only available for NI-STC3 chipsets or is it also valid for STC2 chipsets? Can I send such patterns to STC2 chipsets?

If STC3 is the sole choice,
http://zone.ni.com/devzone/cda/tut/p/id/11556   --- does that mean that the USB-6341 is the closest choice to the USB-6211?

Thanks.
Christophe Content

[ThiCop]

Hello Christophe,

This example needs an STC3 chipset , because it performs a hardware timed buffered  pulse train generation.

In the example they also use one of the LV examples I mentioned before (Gen Dig Pulse Train-Buff-Implicit-Cont.vi) and to be able to use this example you'll need a device with an STC3 chip.

So you'll need an STC3 chipset if you want to use this example.

Looking at the sample rate, analog inputs (16), analog outputs (2) and other specifications the USB-6341 is always equal or better  when comparing with the 6211. So depending on what you want to do this could be a suitable candidate.

If you want to have some more information or a talk with someone of NI, then you can always call your local branch and speak with them about the possible options for your application.

[ThiCop]

Hello Christophe,

One thing I didn't mention before that also could be useful for your situation is the Correlated DIO.

This allows you to use the onboard sample clock to perform HW Timed DIO and for some M-series (Not 621x-series) cards this allows you to output a buffered digital output for example.

Some code examples can be found on:

http://decibel.ni.com/content/docs/DOC-4641

http://decibel.ni.com/content/docs/DOC-4170

The reason I didn't mention this before is because this option is not available for your specific M-series card. This option (correlated DIO) is also available on X-series cards.

In your comparison case you also have a lot more digital outputs available on the X-series card than on the M-series card.

Can you let me know if this helps you further?