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2182a Voltmeter in Hall effect system

2182 Series Support
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JB441616
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2182a Voltmeter in Hall effect system

Post by JB441616 » June 25th, 2013, 9:10 am

I was trying to trouble shoot my Hall effect set up involving the 2182a voltmeter. When turning on the machine it already produces a voltage reading which fluctuates from .0008 to .07mV to .9V reading off around 3 different readings. It sometimes also starts climbing from a small voltage but works its way steadily to -11.9V and just sits there. We isolated it to the point where it is just the power chord with no imputs or output and channel 1 still fluctuates from the three readings or sits at -11.9V. We checked channel 2 and it is much more consistent but is 0.2V steady readings. This seems like a lot of noise and we are not sure where the voltage is coming from.

any thoughts would be helpful, thank you

-J

Dale C
Keithley Applications
Keithley Applications
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Re: 2182a Voltmeter in Hall effect system

Post by Dale C » June 25th, 2013, 10:20 am

Are the channel 1 inputs shorted?
If they are open(not connected) the input resistance of the Model 2182A is more than 10G ohms. This charges up the voltage into an open circit. That is why the reading keeps increasing. If you were to select the 100Vrange you would see the reading be stable with an open input. This is because the input resistance on the 100Vrange is 10M not 10G ohms. It is 1000 times less. Therefore the input does not charge up.
The increasing reading on the 10mV range with an open input is normal.
When you connect to a DUT with a lower impedance this all dissipates.
Go ahead and connect the channel 1 HI to channel 1 LO.
The drift should only be less than 100nV.

JB441616
Posts: 8
Joined: June 11th, 2013, 12:16 pm
Country: United States

Re: 2182a Voltmeter in Hall effect system

Post by JB441616 » June 25th, 2013, 11:35 am

I connected channel 1 HI to channel 1 Lo in the open circuit and the swing dropped dramatically. Thanks for the explanation

However, when i connected it to a DUT (the 7065 Hall effect card) i got swings of 108mV to 75mV to 0.008mV in repetition. The only reason i think this matters is because this is without testing at all, just in the connection phase. Our readings for the Hall effect are in the mV range or lower and i think this noise is resulting in inaccurate measurements.

any thoughts?

thank you

Dale C
Keithley Applications
Keithley Applications
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Re: 2182a Voltmeter in Hall effect system

Post by Dale C » June 25th, 2013, 12:39 pm

When you see this variation in voltage measurements in the 2182A is the HAll Device connected to the current source and 2182A by closing the appropriate crosspoints?
Because it sounds like, from your description, that it is open and not connected.

JB441616
Posts: 8
Joined: June 11th, 2013, 12:16 pm
Country: United States

Re: 2182a Voltmeter in Hall effect system

Post by JB441616 » June 26th, 2013, 5:41 am

From my understanding, the 7065 Card is connected to Both the current source and the voltmeter. Can you clarify cross points?
All i have is the output of the current source to the input of the card, and the 2182a connected to the hi/low inpedence leads (screw terminals) on the back of the card. I am unaware of any more connections needed.

Dale C
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Re: 2182a Voltmeter in Hall effect system

Post by Dale C » June 26th, 2013, 7:12 am

The Model 7065 is a four by five matrix. The cross points of the matrix are made up of relays to connect rows to columsn and such.
The video at this link goes over this.

http://www.keithley.com/centralized_dis ... etid=55820

Also, here is a link to the manual of the 7065. Look at table 3-3. This shows the crosspoints to close for certain connections.
Be aware that the table shows the crosspoints in Column / Row formation.
The Model 7001 that you have shows this as Row / Column. This is reversed because the orignal scanner Model 705 used the Column / row formation.

http://www.keithley.com/support/data?asset=1118

Hope this helps.

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