Manual_Keithley
Keithley Model 428
Never remove these Keithleys for the present location unless you are authorized by the bl staff. Never remove or change the BNC cables.
CHANGE THE GAIN:
press "gain" and move the wheel until you reach the desired gain.
Typycall we use 108 or 109 for Io and 109 or 1010 for Is.
Inside the hutch, set the energy on top of the harmonic. Then read the counders (in the MAIN PANEL.VI). You should read a value betewwn 1 and 10 when the valves are open and a value around 10-3 or low 10-2 when the valves (FE and BL valve) are closed. The saturation value for these keithleys is 10. SO if the value is higher you should decrease the gain.
NOTE: Is keithley 109 does not work for range >4x1011 (15/1/2013)
SET THE FILTER
In order to start the keithley (if for example there is again a fault of the electrical power and the keithley need to be restarted), remember to enable the filter:
1) press the button "filter rise time" in the front panel,
2) move the wheel clockwise until you read 300 mseconds
3) then press the button "filter".
If the filter is not active the spectrum will be very noisy.
Further, if the keithley was off or you need also to to change the gain .
| 109 | 10V=10nA |
| 1V=1nA | |
| 0.1V=100pA | |
| 1010 | 10V=1nA |
| 1V=100pA | |
| 0.1V=10pA | |
| 1011 | 10V=100pA |
| 1V=10pA | |
| 0.1V=1pA |
Counter Settings for these Keithleys:
Io_new (and Is_new, Irel_new)
PC_meter
Address 7
Multiply -1
msecxcycles=1
low=0.01-high 100000
msecxcycle=200
Keithley Model 6430 Sub-Femtoamp Remote SourceMeters
For Io and Is we are using two Keithley Model 6430 Sub-Femtoamp Remote SourceMeters. These instruments are made of a Mainframe and Remote PreAmp. More Details
The two Keithley are located close to the manipulator of the Main Chamber.
The bottom Keithley reads I0, the top Keithley reads IS.
CAUTION!!!!! Do not connect any external sources between Input/Output LO and chassisground. Current exceeding 10.5mA will damage the zener clamp. Such damage is not covered by the warranty. In particular before connecting the Remote PreAmp to the BNC and turning on the Keithley always check that there is overload between the BNC pin and the ground. If there is a finite resistance you can seriously damage the keithley!!! For the same reason ALWAYS disconnect the Remote PreAmp of the Keithley which reads IS from the BNC, after having pressed OFF (on the main panel under the blue ligth: the blue ligth will get off) when you need to transfer the sample because the transfer arm grounds the sample. In any case contact BL staff for more information.
The bottom Keithley reads I0. The Remote PreAmp is generally connected to the BNC on the last mirror of the BL (POSTVERA). However it is possible to measure the reference current I0 also from a grid covered with freshly evaporated gold which is located between the last mirror and the Main chamber. Normally the grid is completely UP. If you need to use the grid you have to move it down with the linear transfer (13 e 3/4 turns), switch OFF the Keithley, disconnect the preamp from the mirror and connect the remote PreAmp to the grid.- Use the Keithley Initialise 6430.VI or more simply from MAINPANEL.VI to turn the keithely ON and set the scale (range) (REMOTE OPERATION).
- The address of I0 is 25. The address of IS is 24.
- The first time initialise I0 (and IS) to 1x10-6 in order to be sure that there is no saturation. Set the value in the The Blue light on the Keithley Initialise 6430.VI and press =>. The Front panel will turn on. NOTE: Instead, to turn it OFF, you should press manually the button on the Front Panel, under the Blue light.
- The possible scales are: 1pA (1x10-12),10pA (1x10-11),100pA (1x10-10),1nA (1x10-9), 10nA (1x10-8),100nA (1x10-7),1microA (1x10-6),10microA,100microA,1mA,10mA,100mA.
- The full scale input for each voltage and current measurement range is 105.5% of the selected range. Once the scale has been set the saturation occurs above 1.05. Input levels that exceed the maximum levels cause the OVERFLOW message to be displayed on the front panel of the keithley and constant readings (e.g. if the scale was set to 1x10-9 and the current is 2x10-8 you will read 1x10-9).
- The typical scales used during the measuremnets are from 1x10-9 and 1x10-7
- If the instrument displays the OVERFLOW message on a particula rrange, select a higher range until an on-range reading is displayed.
- Use the lowest possible range without causing an overflow to ensure best accuracy and resolution.
