PCI 6250

[wang]

Hi,

Can PCI 6250 measure the analog DC current using DAQ Assistant?

Can PCI 6250 act a current meter to CB-68LP board and connected to PCI-6250 board?

Why PCI 6250 board has no BNC connector terminal, just lead cable connector terminal? What is the difference between these two?

Many thanks if you can replay to me promply

[Otis]

Hi Wang,

1. The M-Series devices are only capable of directly measuring voltage. 
   
1. If you want to measure current then you will need to measure the voltage across a known high-precision resistor.
2. If you connected a high-precision resistor (see point 1) between the points that you're measuring (ie aiN and aiN+8 for differential or aiN and aiGND for RSE), then you can read the voltage drop and find the current.  See the M-Series Help for pinout information for your NI 6250.
   
3. If you need a BNC connector terminal then you may want to look at the BNC-2110.
   

I hope this information helps.

Regards,

[wang]

Dear Otis:

Thanks for your solutions. I would to ask if I have a test fixture with an analog Direct Current output. In my block diagram,

the output is measured by a current meter. How can I measure this ouput for DC current?

Is it OK to put resistor between AI0 and AIGND on CB-68LP connector board using PCI-6250?

Because you are measuring a voltage across a resistor in parallel using CB-68LLP. I am not very sure.

This is right way to do even though your block diagram is designed using Crrent Meter?

Regards,

Wang

[Otis]

Hey Wang,

It sounds like you need to be measuring your current by simply reading the voltage drop across a resistor.  I did a simple search on ni.com for "current input daq" and found the following KnowledgeBases:

Measuring Current Using the Analog Input of a DAQ Board
What National Instruments Products Support Current Input?

Regards,

[wang]

Hi,

Did it mean I must put a resistor across the connector,CP-68LP board to measure DC current for PCI-6260 DAQ board?

Even though my block diagram of my test fixture put digital multimeter to measure current, I must put a resistor across

CP-68LP to measure it?

[Dennis_Knutson]

When you use the DMM, do you set it for voltage or current? If you set it for voltage, then the fixture was designed with a resistor in series so that you could measure the voltage drop across it and calculate the current. If you set the meter for current, then you have emulate the meter's circuitry by placing a precision resistor on your CP-68. You've been told numerous times that the 6250 board can only measure voltage. You'd better study the schematics of the test fixture to understand exactly how it works.

[wang]

Hi Otis:

1. The M-Series devices are only capable of directly measuring voltage.

     What if my signal is a digital TTL signal, can 6250 measure current?

2. You said if I need a BNC connector terminal, I may want to look at the BNC-2110.

    That means BNC-2110 can connect to 6250 DAQ boards, right?

     If so, what is the difference between the NI 5112 and PCI 6250 boards? Why do I need to use NI 5112 to capture waveform like a scope?

     I know NI 5112 is a digitalizer. What is the definition of digitalizer? Can you explain? Is NI 5112 defined as DAQ boards?

     I hope you can answers all of these because I doubt.

3) I am actually set the meter for current. According to your previous mail, I have emulated the meter's circuitry by placing a precision

    resistor on your CP-68. Did you means the same thing? I can not measure analog DC current using CP-68 and 6250. I can

    only measure the voltage. Did it mean that? I would like you to clarify me. Thanks.

[Dennis_Knutson]

It seems you keep asking the same question over and over again. The DAQ board only measures voltage. With a precision resistor, you measure voltage and calculate the current in your program. It seems you've already done this so I don't understand where the confusion is.

The 5112 is a specialized data acquisition device. Each channel has a dedicated Analog to Digital converter so data can be simultaneously acquired. It has a much higher sampling rate. It has a dedicated trigger input. It has either AC or DC coupling. It has selectable input impedance. In other words, the 5112 is designed to act as a benchtop oscilliscope and the software that comes with it is written to provide the same user interface and functions of the benchtop scope. The 6250 can be made to behave like a scope in certain conditions. It has more vertical resolution (16 bits versus 😎 but a slower sampling rate. You cannot do true simultaneous acquisition but you do have 16 inputs instead of 2. It is DC coupled only. Can you use the 6250 instead of the 5112? I don't know. I have no idea of what the signal you're trying to acquire is like. It sounds like it someone else besides you that made the decision to purchase the 5112 since you don't understand the differences between the two boards. If it wan't you, is that person still around to talk to? 

[AnalogKid2DigitalMan]

Wang:

It sounds like you require the assitance of an electrical engineer or electronics technician in order to complete your project. Is there anyone at your facility that could assist you directly? I am assuming that this is business related.