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Problem: Differential mode, measures 1.4 V, USB 6009

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Hi everyone

 

I'm measuring charging and discharging two capacitors, individually.

 

I'm using the USB 6009;

 

Two capacitors, two graphs, two analog inputs (AI0 +, AI01 -) and (Al1 +, Ai1 -);

 

I configuredin differential mode; ok

 

Problem:

When a capacitor is switched off, it measures 1.4 V

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Do you have a schematic of your circuit?  What is happening when you turn the switch off?


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Hi, Sorry my english is not very good..

 

 

What is happening when you turn the switch off?

 

R:   USB 6009  Analog Input Reads Approximately 1.4 ,

 

Thank you

 

 

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Let me rephrase that.  What does your circuit do when you turn the switch off?  Is the capacitor left there with nothing connected?  Do you connect something to drain the charge on the capacitor?

 

SHOW US YOUR CIRCUIT'S SCHEMATIC.


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Message 4 of 9
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Thanks for your help!!  croossrulz

 

What does your circuit do when you turn the switch off?

R: The capacitor discharges, 0V.

 

Is the capacitor left there with nothing connected?  Do you connect something to drain the charge on the capacitor?

R: Resistor  1M

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Sorry!!

 

What does your circuit do when you turn the switch off?

R: The capacitor discharges, and Usb 6009 Analog Input Reads Approximately 1.4V ..... I want to 0V..

 

Thank you

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Solution
Accepted by topic author Saille

Try setting up the task correctly-  Use the DAQ Wizard to create the TaskSmiley Wink

Capture.PNG

Dev1/ao0  would be much better-  Oh, and now that you have the Wizard open-  Do look at the wiring diagram it provides you withSmiley Very Happy

For 6009 DIFFERENTIAL mode task AI0 is + AI3 is - and you only reserve explicitly reserve AI0 (The AI3 line is reserved by seleting the + line in the channel and declairing that it is differential)

 

And give the Task/Channel a meaningful name  "MyCap1Discharge" would be helpful.......

 

Now let's speak about your electrical engineering:

The input impedance of the 6009 is 144kOhms  The 1MOhm discharge resistor becomes moot as soon as you connect the monitoring 6009 AI.


"Should be" isn't "Is" -Jay
Message 8 of 9
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Thank you Jeff Bohrer

Thank you Crossrulz

 

Sorry my english is not good

 

well, the circuit worked, I removed the1M resistor and put 10k

 

Saile

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