Null offset DMM 4070

[Tonnie]

Hi

How to programm the null offset in C# using the class library from the DMM4070

I want to use the "null offset" from the DMM 4070 softfront pannel in my programm but i can't find a method for it

Thanks in advance

tonnie

[nyc_(is_out_of_here)]

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@Tonnie wrote:

Hi

How to programm the null offset in C# using the class library from the DMM4070

I want to use the "null offset" from the DMM 4070 softfront pannel in my programm but i can't find a method for it

Thanks in advance

tonnie

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What does the programmer's manual say?

[Tonnie]

Hello

I looked in the helpfile that came with the class library of the DMM4070 but i can't find info about the "null offset"

We want to do a resistor measurment and for that we want to set the DMM to null by shorting the testneedles on our needle bed to compensate the kables

In the softpannel of the DMM there is a button called "Null Offset". This function i want to use in my code

[nyc_(is_out_of_here)]

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@Tonnie wrote:

Hello

I looked in the helpfile that came with the class library of the DMM4070 but i can't find info about the "null offset"

We want to do a resistor measurment and for that we want to set the DMM to null by shorting the testneedles on our needle bed to compensate the kables

In the softpannel of the DMM there is a button called "Null Offset". This function i want to use in my code

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What you have just written above answers nothing about reading the programmer's manual for the instrument.

[ThiCop]

Hello Tonnie,

Have you already looked at the Programming Reference titled "Programming with NI-DMM" in the NI Digital Multimeters Help?

Some functions that maybe already could help you on the way are the following ones:

niDMM_ConfigureOffsetCompOhms

niDMM_ConfigureAutoZeroMode

[Tonnie]

Hello Thierry

No those functions don't help me. I think that those 2 functions are not the same as the "Null offset" from the frontpannel of the DMM.

We have now created our own offset by measuring the resistance with  shorted lines and substract this value from the second measurment where we measure the resistance of the load.

Still i find it strange that we can't do an offset compensation in the DMM self.

Or is it may only possible in Labview and not in CVI or C# ?

[ThiCop]

Hello Tonnie,

I had misunderstood your request clearly.

I thought you were looking for more information into specific types of "automated" offset nulling.

If you just want to implement the offset nulling checkmark behavior, then you can do this quite easy.

I thought you had already seen this by going to the Soft Front Panel its help.

The functionality of this checkmark/button is quite simple (taken from the help):

"Null Offset stores the current reading of the DMM and subtracts it from any future readings. The stored offset is shown on the display. When enabled, the Null Offset value is updated if the device, function, or range is changed."

 So basically this just comes down to defining a button or checkmark that:

1 Stores the current actual reading (without this software based offset nulling) in a variable x at the moment when your button goes from "disabled" to "enabled" state. (eg. moving a switch from off to on)

2 While this is enabled you will subtract your offset from any current reading as a sort of very simple software post-processing. (eg. switch still in on-position)

3 When you go back from the enabled state to the disabled state, you reset the variable x to zero/0 value (eg. switch from on to off)

4 When you are in disabled state (eg. off-position of your switch) , then you just read the actual readings + your variable x (=0).
  This comes down to just reading the actual reading (without the software based zero offset.

5 You will wait until you again go from the disabled to the enabled state. If this happens, then do step 1 again.

So basically, you just need to add an offset value to your actual reading and set this offset value when you do a transition of disabled to enabled state or from enabled state to disabled state.