How to configure the Model 6220/6221 and 2182A for Delta Mode?

The Keithley Models 6220 and 6221 Current Sources are designed to work with the Model 2182A Nanovoltmeter to measure very low resistances. A good method of doing this is called the Delta Method as described in the Keithley Low Level Measurements Handbook. The following instructions can be used to configure a 622x/2182A combo for Delta Mode measurements via the front panel. Once configured for Delta Mode, the pair of instruments are effectively controlled from the 622x.

Equipment List:

• 622x Current Source

• 237-ALG-2 Triax to Alligator Clip Cable

• 2182A Nanovoltmeter

• 2107-4 Low Thermal Input Cable (Alligator Clips connected)

• CA-351A Communication Cable, RS-232

• 8501-2 Trigger Link Cable

Hardware Set-Up:

1. Connect the RS-232 and Trigger Cables as shown
   

2. Connect the 237-ALG-2 Alligator Clip Cable to the output of the 622x and the 2107-4 Low Thermal Cable with alligator clips to the input of the 2182A. Connect the HI terminal of each instrument to one end of the resistor and the LO terminal of each instrument to the other end of the resistor as shown in the drawing below.
   

Setting up the 2182A from the Front Panel:

1. Restore to factory default conditions by pressing RESTR, select RESTORE:FACT, and press ENTER.

2. The 2182A must be in RS-232 mode. Set the 2182A to RS-232 mode by pressing SHIFT, RS-232, and setting it to ON.

3. You will then be guided to set the Baud rate, flow control, and terminator characters. These should be 19.2k BAUD, Flow control of XonXoff, and a terminator of CR. The instrument will then return to the home display.

Setting up the 6220/6221 from the Front Panel and configuring Delta Mode:

1. Restore factory default conditions be pressing SETUP.  Select PRESET and then ENTER.

2. Set to GPIB mode by pressing COMM and selecting GPIB and then ENTER.

3. If you encounter errors, before setting the 6220/6221 to GPIB, ensure the RS-232 settings match the Baud rate, flow control, and terminator settings of the 2182A you set above.

4. For high resistance DUT only, use guarded operation.  Press the TRIAX key and then select INNER-SHIELD and ENTER. Select GUARD and then ENTER. By doing this, the LO terminal will be on the green lead the black lead will be at guard potential.

5. Set-up the delta function. Press CONFIG and then DELTA and set the following parameters:

               I-HIGH and I-LOW: Set to desired magnitude and press ENTER. I-LOW will automatically set to the same magnitude but negative polarity of I-HIGH.

               DELAY: Set desired delay time and press ENTER.

               COUNT: Set to INFINITE.

6. To measure in ohms, press UNITS and select OHMS.

7. Arm the delta mode by pressing the DELTA key and press the TRIG key to begin taking measurements.  Abort the delta operation by pressing EXIT.

8. To recall individual readings that are stored in the Delta mode, press RECALL. Use the Range Arrow keys to change the reading number. Press EXIT to get out of recall mode.

9. To view statistics of the data taken, press RECALL and then EDIT.  Press ENTER to change the value from Minimum to Maximum, Average, Standard Deviation, and Peak-to-Peak values.