keithley foces (unwanted) 0V (=short) after communication

[soleme]

Hi,

I've made a program that uses Keithley driver.

I force 1 certain voltage on my device, put output on and measure the current with a agilent meter.

After I put the Keithley output off again.

But the problem is after this communication, the  the Keithley gives internally a short (0V) while it should be an open.

(Like it is before I do communcation)

Has somebody any idea how this can be solved?

Thanks,

[Omar_II]

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@soleme wrote:

But the problem is after this communication, the  the Keithley gives internally a short (0V) while it should be an open.

(Like it is before I do communcation)

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I do not understand the "internally a short (0V) while it should be an open"

I would expect the after I turn off the output of the power supply it should read 0 volts (or close to it).

But depending on the design of the power supply I might not never see an open across the output (solid state relays)

Even when it is powered down.

How do you know it is not open? Ohm meter? Unless the power supply has mechanical output relays, if you try to read the impedance of the output with an ohm meter you will most likely NOT see an open (infinity) but instead will see some leakage.

If you are just setting the output voltage to 0 and not turning off the output, then when you put your ohm meter across the power supply output the power supply will try to maintain the 0 volts and you could look like a short to an ohm meter. Worst case you could damage your ohm meter.

[soleme]

Hi,

When I measure manually:

I always measure a high impedance on the output.

After I've put a voltage on the port and put it off again I measure still a high impedance.

When I use Labview, before I force anything I have also a high impedance, but after the communication I got a 0ohm resistance (=0V).

I have to unplug the power supply to get the again the high impedance.

On Labview there's a subvi where you can set the high impedance but this block doesn't seems to do anything on the Keithley.

Sven

[johnsold]

It has been some time since I used a Keithley source, so I may be mistaken.  I seem to recall that the device had a command to set the output on or off as well as different commands to set the voltage.  With the output off you probably get high impedance.  With the output on and the voltage set to zero, I would expect the short circuit-like performance which has been described by others who responded.  Check the programming manual for your device to see if you can turn the output off.

Lynn

[soleme]

Hi,

I'm able to put the output off.

But my 0V on the output remains, and I still don't get my high impedance.

Sven

[Omar_II]

It too has been years since I have worked with a Keithley supply.

Have you tried sending a power on reset command to see if the Keithley supply will reset itself to it's power on state?

You might need to address this problem to Keithley.

[soleme]

Hi,

I found a way to go around this problem.

After I force a voltage, I initialize the Keithley again to force a current (but I don't force a current) and then I put off the output and stop the communication.

-Because the Keithley stays high ohmic when he's in current forcing mode.-

It's a trick, and if you follow on a scope the Keithley is doing some strange things but it's good enough for me.

And nothing else worked, I tried all the subblocks without success.

Sven