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  • Author Author: Jan Cumps
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Programmable Electronic Load - Write a LabVIEW Library part 2: Read Output Block

Jan Cumps

Peter, Jon and I are building a Programmable Electronic Load. In this series of blogs I'm building a LabVIEW library of reusable components

 

image

 

 

In this second article: Reading the the instrument's measurements

 

LabVIEW has a set of blocks to build flows with serial communication devices. Those blocks work well with our instrument.

However, inspired by the example for (in this case) the BK Precision 91xx family, I'm going to create more abstract blocks.

 

Read Output Block

 

image

 

This blog reads the values sampled by the instrument. I've used the same options as the BK Precision lib:

0: VOLT

1: CURR

2: POW

3: DVM

4: RES

The bold ones are implemented by the firmware. The others are for future use (and to stay as true as possible to the lib that inspired this) will throw a SCPI error.

 

image

 

For the Initialize block, the input parameters are

  • VISA resource name eload
  • delay before read (ms)
  • Measurement Function
  • error in (no error)

The output parameters are

  • VISA resource name out
  • Measurement
  • error out

After running this block, the following functionality is performed:

  • The measurement option that's passed to it is performed

0: VOLT

1: CURR

2: POW

3: DVM

4: RES

  • If an error is detected, the VISA resource is closed and error info is passed to the caller.
    Else the block passes the measured value to the calling flow via the Measurement parameter.

Reading the Output

The block is simple to use. It expects that you've initialised the instrument with the Initialize block.

image

Depending on the value you pass (in this example 1: current), it will return the last value sampled by the instrument.

 

LABView blocks
LabVIEW Library part 1: Initialise Block
LabVIEW Library part 2: Read Output Block
LabVIEW Library part 3: Close Block
LabVIEW Library part 4: Function Set Block
LabVIEW Library part 5: Input Control Block
LabVIEW Library part 6: Raw DAC Block
LabVIEW Library part 7: Raw ADC Block
Real World Examples
Programmable Electronic Load - Automating a DC Switcher Efficiency Test with LabVIEW
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  • Jan,

     

    Great write up. The LabView seems to have a pretty clean interface.  I have seen quite a few groups using this to construct test beds, but I have never got around to trying it.  Is it worth the cost/effort to learn it?  I have used LabWindows/CVI before an I was not a fan.  Hopefully LabView is better.

     

    Keep up the good work!

    Gene

  • in reply to genebren

      wrote:

     

    .... The LabView seems to have a pretty clean interface.  I have seen quite a few groups using this to construct test beds, but I have never got around to trying it.  Is it worth the cost/effort to learn it?  I have used LabWindows/CVI before an I was not a fan.  Hopefully LabView is better.

    ...

    I paid $ 43 for the home and student edition 2014 (from Digilent. I used a $7.5 coupon that Digilent published when they were on The Amphour).
    For me it's worth the effort because I want to know how to develop with it. It's a desired skill on the market.

     

    I don't know LabWindows/CVI so I can't compare.

  • in reply to Jan Cumps

    Jan,

     

    It is good to have skills, especially marketable ones.

     

    Gene

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