Fatal error in Keithley 2450

Hello, I have used the Keithley 2450 SourceMeter for measuring sheet resistance of samples.

The other day, co-researcher in my lab asked me to source 2V and check if any current value is measured on HZO sample.
After I turned on the Keithley 2450 SMU, HOME of which showed the continuously changing current and voltage values, 
I selected the function of measuring current and sourcing voltage, enabled the auto range for V, I and set 2V for sourcing voltage.

Then, I located one probe connected to Force HI to (+) electrode and the other connected to Force LO to (-) electrode in the probe station.
As far as I know, Molybdenum (Mo) is used for the both electrodes.

When I came back to Keithley 2450 SMU to check the results, the voltage value was stopped at the strange value, like 0.04V? and the current, too. I was about to try again, but the SMU didn't response for the button I pushed. So, I power cycled the SMU, but HOME screen didn't show any values unlike until now. And, when I clicked RANGE in the HOME screen, a blue screen appeared with telling me the instrument has encountered a fatal, unrecoverable error like the image I uploaded.....

I've entrusted the repair to the company, because they said the motherboard is faulty and needs replacement. However, separately from the repair, I want to know the reason of fatal error to prevent future issues. That's why I explained the situation before I noticed the malfunction of the SMU in detail. The company mentioned they also don't know the exact cause either, so I'm writing here for assistance.

Any advice or comment for the reason of fatal error with blue screen will be really helpful for me and our lab !! ;)

 

A fatal error is rarely related to the test setup. It can possibly happen if the instrument is connected to a setup that damages the SMU, but nothing of your description indicates a hazardous setup.

A few thoughts on your description though:

• The instrument is expected to show fluctuating voltage/current readings on the Home screen on startup. By default, the 2450 starts up into the Normal Output off state in Source V/Measure I mode. This sets the instrument to source 0V, and it reads V and I continuously. The instrument will go a low range with autorange and read/display noise.
• In general, connect your entire setup before turning the output on, I'm not sure if you did that based on your description.
• When performing a test like you described, where you're sourcing a voltage and not sure if you will see current, the current limit is very important. The current limit setting is in the bottom right of the Home screen, the default is 105mA. If current does appear across your sample, and it tries to increase beyond the current limit setting, the SMU will stop being a voltage source and instead become a current source; similar to how power supplies operate when they reach their max current setting. Decide the maximum amount of current/power you'd be comfortable going through your sample and set the current limit appropriately.