Keithley 2001 and 7001 combo for 4 wire resistance measurement

[Grugh_Mike]

I need to measure /scan the 20 thermistors in 4 wire measurement.

I am using Keithley 2001 along with 7001 mainframe with 7011 card.

I have done the connections in 7001 card for 4 wire measurements and the DUT are connected.

In the front panel, i set all the channels of 7001, ie make all channels from 1 to 20 closed.

and then executes the program.

Kindly verify whether my developed program would work without any flaws.

Thank You in advance.

Main vi: Keithley 2001 and 7001 measurement.vi

Attached are the vi's.

[Grugh_Mike]

Also Please let me know where the address for the scanner card is to be set.

ie: 1!1 to 1!20.

I could not find that particular option anywhere.

[johnsold]

Grugh Mike,

I have not worked with either of those instruments, so my remarks are general rather than specific.

1. It seems likely that you will need to create a channel for each RTD (4 switches).

2. I think it can only measure one channel or RTD at a time.

3. If my assuptions in 1 and 2 are correct, you will need close the specific channel for the RTD being measured, read the resistance, then open the chennel.  After competing that process for one channel, select the next channel and repeat until all RTDs have been measured.  A for loop makes this easy.  If you want repeated measurements on the same group of RTDs, enclose the for loop in another loop, either for or while depending on whether you know in advance how many cycles you need.

Lynn

[Grugh_Mike]

Dear John

I agree with you.

But where will i enter the address to the specific channel.

In the present blocks for K2001, there are no inupts for addresses.

How can i direct each single measurement to specific channel?

Please help.

[johnsold]

The 2001 does not have channels.  It just measures the signal connected to its inputs.  The 7001 has channels.  You specify those in the Channel List array on the Keithley 2001 and 7001 measurement.vi or something similar.

What I would do is to create that array of channels, one channel per RTD. The put the Open/Close Channel VI inside a for loop.  Use autoindexing to select the channel.  Inside the loop close one channel, read the resistance, and open the channel. 

Those driver VIs are quite old and are not written to modern coding style guidelines, so do not be afraid to make copies and then modify or clean them up.

Lynn

[Grugh_Mike]

Dear John

Selectively opening and closing the 7001 scanner is of no problem.

But how to prompt the Keithley 2001 to scan a particular address.

For example:

In 7001 scanner, i close the Scanner 1 channel 1 relay (ie 1!1) and leave all others open.

Then, how can i direct the Keithley 2001 to scan that particular channel (1!1)?

I am no that good in VB,

Please help by explaning what to change in the BD.

Thank You in advance

[johnsold]

Grugh Mike,

The 2001 reaaly does not know or care what channel is being measured.  It just measures whatever is on its inputs. Your program needs to keep track of which channel is  being measured.  The for loop can do that for you automatically.  As it autoindexes through the Channel List array, it will also autoindex the measurements outputs to another array where the measurements appear in the same order as the channels.

The Getting Started with LabVIEW tutorials are a good place to begin with understanding how to make a loop work for you.

Lynn

[Grugh_Mike]

Dear John

I have tried scanning using the K2001.

At first, the front inputs were scanned (as the front input button was pressed) and none other.

Later, when i pressed the rear button, it showed infinite resistance (ie not connected).

Are you sure that K2001 will automatically scan by finding out which input is to be scanned (considering we have 4 options- Front input, rear input, rear scanner and external scanner) ?

How to scan from the external scanner?

[johnsold]

I have never used these instruments, so you will need to study the manuals or find someone who knows the instruments.

Lynn

[Grugh_Mike]

will the attached source do any good ?