keithley 2000 voltage measurement

[poli]

Hi,

I want to write a code to display the voltage measured from a keithley 2000 meter using RS232 serial port  and display it on a   graph using Labview 8.5 on Windows Vista based Laptop

. I guess the first step is to download the driver for keithley2000 http://sine.ni.com/apps/utf8/niid_web_display.model_page?p_model_id=248. I want to go step by step. Please give me the main key steps on how to proceed on this problem and i will then work in detail based on your directions.

How do i know that laptop  is recognizing the meter and RS232 connection is sound? What are the next key steps i need to work on? Please give the directions.

Thanks

[Dennis_Knutson]

Besides downloading the driver and installing it, you will want to check out the Learn section of the Instrument Driver Network. Before using driver, you should open MAX (Measurement & Automation Explorer) and verify 1). That the serial port is listed under DEvices and Interfaces>Serial & Parallel. 2) NI-VISA is listed under Software. Then you can right click on the serial port in MAX and select Open Test Panel and click the Basic I/O tab. You can use this to Write simpple commands that are listed in the manual and do a read. You can also use a terminal emulator such as Hyperterminal. Both of these will verify that you have the com settings correct on the pc/instrument and that you are using the correct type of serial cable. check the instrument manual for the type to use. There are two basic types and you have to use the correct one. After you have done all of this, then open the driver and look for an example. Run that.

[poli]

In the suggestion by dennis , it is stated there are two types of serial cable and i must use  the right type.

What are the two types? Does he mean a 9 pin serial port and a 25 pin serial port? please clarify. My serial port on keithley meter is 9 pin.

Thanks

poli

[Dennis_Knutson]

There are different types of cables for 9 and 25 pin connectors but I was refering to null-modem or straight-through types of cables. A null-modem cable transposes the tx and rx pins (at least). In other words, pin 2 on one end would be connected to pin 3 at the other and vice versa. For a full null-modem cable, other pins may also be cross-connected. A stratight-through cable is just what it sounds like. Every pin at one end is wired to the same pin at the other. The instrument manual should explain the correct type to use.

[poli]

Thanks for the earlier tip, the keithley manual says i need straight through cable and so i will use that type only.

My requirement is to plot the voltage measured by keithley multimeter such that every 10 millisec a reading  is acquired.

That is the sampling frequency is 100Hz. How do i ensure this requirement in my labview code? Often people set  the baud rate- will varying this change the sampling frequency?

[F._Schubert]

For fast reading, it is important not to use the MEAS? command, but READ followed by FETCH? (if I remember correctly). Normally these DMMs operate at 1 PLC (power line cycle -> 50/60 Hz), so you need to adjust the NPLC (number of power line cycles).

There is to options to work with the Keithley DMMs inside LabVIEW. You could use the LabVIEW drivers for the Keithley 2000, those can be found on ni.com and on the keithey homepage. Propably they only implement GPIB, the you need to make some modifications on them for RS232. The other option is to send the commands as found in the DMM manual via VISA.

Felix