How to acquire fast direct-current signal using Keithley 6485 using Rs-232

[ak47raj]

Keithley 6485 Picoammeter, DC signal (fA-pA), RS-232, Fast acquisition: reading per 0.01s

I am new to instrument programming and Labview. I am trying to do fast current measurement at the speed of some 100 readings per second (let us say). Is it possible to do this over Rs-232, reliably? Can I program and use my instrument with aid of Labview to this task?

All kinds of help, advices appreciated.

[crossrulz]

I recommend downloading the driver from Keithley: http://www.tek.com/specialty-instruments/6485-software/models-6485-6487-and-6514-ivi-visa-based-driv...

[ak47raj]

Thanks a ton.

I have this driver already and I am using it in a program. But the question is about the fast acquisition mainly. Till now my program reads 1 value per 2 or 3 seconds.

Is doing the same at faster rate a reliable method. Is the main question.

[crossrulz]

This advice is based on experience with another Keithley meter.  I'm assuming this instrument will behave the same (I have not looked at any specs).

The instrument should have some built-in memory for storing data at a fast rate.  So you tell the instrument to connect X samples at Y rate.  You then wait for the data to be aquired and then ask for the data.

Depending on the instrument to spit out measurements through the serial port much faster than a few samples per second is not likely to work.

[ak47raj]

Could you please elaborate this in terms of labview programming. Keithley 6485 has an internal buffer to store 2500 readings. But I might need to acquire data points more than this value, over a period of time.

[Dennis_Knutson]

If you need more data, you will need to perform multiple scans. There will be a delay between scans in order to read and flush the buffer. If you need continuous readings, you have the wrong instrument.