scaling

[ceilingwalker]

Hello. I have an analog input that I am trying to scale. It is driving a power amp with 0-5VDC. They would like to have a 0-10VDC signal, to get more data. The amplifier fully conducts at 5VDC, even though I placed max=10, and min=0, on the DAQ mx. I read through some scaling information on th NI sight but found nothing that worke. Thank you for your time.

[aeastet]

First I'm not sure how you think going from 0-5 to 0-10 will get you more data. Your DAQ card has a resolution (i.e. 12 bit, 16 bit, 24 bit) changing the scaling does not change the resolution.

Having said that do you have a daq card that can output 10VDC? What sre you using? How is your circuit made? More information here would help. Also I am not sure if you are reading or writing the signal? That was really clear on reading your question again. My understanding is that you want to be able to generate a 0-10VDC signal.

[ceilingwalker]

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@aeastet wrote:

First I'm not sure how you think going from 0-5 to 0-10 will get you more data. Your DAQ card has a resolution (i.e. 12 bit, 16 bit, 24 bit) changing the scaling does not change the resolution.

My first LV project, I can only go by what the design engineer wants. I had it set 0-5 VDC, he want's it changed to 10. I just do as I am told, or at least try.

Having said that do you have a daq card that can output 10VDC? Yes, I have a USB-6002 and it will output 10 VC.What sre you using? How is your circuit made? Not sure what you mean by how my circuit is made. More information here would help. Also I am not sure if you are reading or writing the signal? I am writing to DAQ mx Create Channel, setting min to 0 and max to 10.That was really clear on reading your question again. My understanding is that you want to be able to generate a 0-10VDC signal. I am able to easily generate the 10 VDC, however, it makes no difference when driving the power amp. Even when I drive it 0-10 it only makes changes at 0-5VDC so, once my output has reached 5, it is driving at 100% power, anything over 5 VDC does nothing, as the amp is already at full power. I was thinking maybe this is the only voltage the amp can run at is 0-5VDC.

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@aeastet wrote:

First I'm not sure how you think going from 0-5 to 0-10 will get you more data. Your DAQ card has a resolution (i.e. 12 bit, 16 bit, 24 bit) changing the scaling does not change the resolution.

Having said that do you have a daq card that can output 10VDC? What sre you using? How is your circuit made? More information here would help. Also I am not sure if you are reading or writing the signal? That was really clear on reading your question again. My understanding is that you want to be able to generate a 0-10VDC signal.

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[aeastet]

What is the model number on the power amp? If you are sure that you are outputting the 10VDC signal then I would expect that you need to set the amp up to 0-10VDC or that it is not capable of 0-10VDC. If you have put a meter on your output and you are getting 10VDC then it is probably not what you are doing in the software. The only other thing that I would suggest is make sure you have the current to drive the output. How much current does it take to drive the input for the power amp? The DAQ output willhave a current limit. Many times it is a small ammount.

[ceilingwalker]

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@aeastet wrote:

What is the model number on the power amp? Marchand VT3 (0-200V). I called manufacturer and because they are almost all custom made, there is no literature for it. If you are sure that you are outputting the 10VDC signal then I would expect that you need to set the amp up to 0-10VDC or that it is not capable of 0-10VDC. This is what I am trying to find the answer too and without any literature, it is difficult. I only reads 0-200V, 20 Amps max, on the front of it. If you have put a meter on your output and you are getting 10VDC then it is probably not what you are doing in the software. I have a scope on the output from the NI DAQ card and it is going to 10 volts however, after 5VDC to amp, it is at full voltage. The only other thing that I would suggest is make sure you have the current to drive the output. How much current does it take to drive the input for the power amp? The DAQ output willhave a current limit. Many times it is a small ammount.

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[aeastet]

So what you are saying is when you are inputting 5VDC the power amp is outputting 200V? If that is true then I would think that your input for the power amp is 0-5VDC. Changing it to 0-10VDC does not make a difference because the amp is not capable. The only one that could answer that is the manufacturer.

On the flip side of that though it really shouldn't matter. if you can send a 0-5VDC signal to the power amp and it goes from 0-200V like it should then everything is ok. Changing the scaling on the output really would not get you more accuracy or resolution anyway. If you can get me a better idea of what you are looking to provide to the people requesting this change maybe I could help you give them what they are looking for.

[ceilingwalker]

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@aeastet wrote:

So what you are saying is when you are inputting 5VDC the power amp is outputting 200V? Yes Sir. If that is true then I would think that your input for the power amp is 0-5VDC. Changing it to 0-10VDC does not make a difference because the amp is not capable. The only one that could answer that is the manufacturer. Kind of what I figured but being new to LV I wanted to make sure there wasn't something else I could do.

On the flip side of that though it really shouldn't matter. if you can send a 0-5VDC signal to the power amp and it goes from 0-200V like it should then everything is ok. Changing the scaling on the output really would not get you more accuracy or resolution anyway. If you can get me a better idea of what you are looking to provide to the people requesting this change maybe I could help you give them what they are looking for. Here is the reason he wants it changed: If he changes the input from 0-5 to 0-10 he will be able to read more plot points on the scale so, instead of 5VDC=200 Volts (how it is now), 5VDC=100 Volts, if we are able to scale 0-10VDC.

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[ceilingwalker]

Really, the bottom line is, he thinks he will get more plot points using 0-10 than he would at 0-5, which in theory sounds feasible however, I am thinking this amp will use the first 5 volts and nothing else.

[aeastet · Accepted solution]

It should not change anything. Without more information from the amp there is really nothing else you can do.

[ceilingwalker]

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@aeastet wrote:

It should not change anything. Without more information from the amp there is really nothing else you can do.

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I just heard back from manufacturer, 5 volts max. I sure do appreciate your time Sir. Thank you.