Keithley 228 power supply

[desmond tay]

Hi, i have written a labview program to control the keithley 228 power supply. If i input 5V and 1A into the power supply from my front panel when the power supply is turned on, the power supply display panel will display 5V and 0.2A. The 0.2A is the current which is drawing by the DUT. My question is if i were to display the 0.2A onto my labview program on the front panel, i need to input a 1000ms into the timeout of the GPIB read function, inorder for the current to display out. If i input less than 1000ms, the current is unable to display out. But i need fast reading and measurement, the 1000ms input into the GPIB timeout have affect my testing. My hardware configuration consists of the keithley 228 power supply, 7053 switch card and 7002 switch box.

I have tried using the 228 driver from the NI web, but it don't seems to work. You may take a look of the attachment file of my written VI. Please advise.

Thank you.

[GerdW]

Hello desmond,

the timeout is the max amount of time the GPIB command waits for the device to answer. The default value is 10 seconds. The device normally answers faster, but you cannot force it to be faster by setting a small timeout value...

But: normally the Keithley should answer faster than 1 second ... (Maybe I could test this on my older K220/230/706 devices?) What does your manual (or Keithley support) say to this behaviour?

[LV_Pro]

Is the current to the DUT stable within 1000mS? I have a unit that takes over a second to stabilize and during that time the current is changing. It may be that the Keithley waits for a stable output before giving a reading.

P.M.

[desmond tay]

Hi,

How to check whether the current to the DUT is stable after 1000ms. But when i put a probe at the output of my GPIB read, i am able to read 0A when the power supple is off. It display an empty string(blank) when the power is turn on.

And when the timeout is set to 900ms, the reading will display on(0.2A) and off(empty string). Meaning sometimes it's able to read, sometimes unable to read.

Thank you.

[Albert.Geven]

Hi Desmond

Try to add an extra endcharacter to your string.
I saw that you rely on EOI (End or identify) and the keithley should respond.
But maybe it is faster in mode 3 (add CRLF)
I'm talking about the send/read data
Furthermore...
You are using a sequence frame for sequencing the write and read..
You can use sequence by wiring instead.
See case 3 of your vi.