Keithley 705 Instruction Manual page 22

7. Press INTERVAL, 0, 0, 3, 0, 0, 0, ENTER. (Programs the
interval time for three seconds.)
8. Press CHANNEL, RESET. (Turns on the CHANNEL LED,
selects the channel mode for display and resets the Model
705 to the programmed first channel.)
9. Press CONTINUOUS. (Selects the continuous scan mode
and turns on the CONTINUOUS LED.)
10. Press START/STOP. (Initiates the continuous scan mode
and turns on the START/STOP LED.)
grammed to scan five separate low current sources. Also, the
following parameters will be programmed into the Model 705.
1. First channel is 1.
2. Last channel is 5.
3. Interval time is 2 seconds.
4. Use the single scan mode.
Use the following procedure to program the Model 705 for this
example:
As in the previous examples, the scanning sequence can be
stopped at any programmed channel by pressing the
START/STOP button. Pressing the START/STOP button
during a continuous scan stops the scan at the presently
displayed channel, the channel remains closed, and turns off
the START/STOP LED. To resume the scanning sequence
from the presently displayed channel, press the START/STOP
button. The START/STOP LED turns on when resuming the
scan.
1. Assume
that there are the five low current sources to be
scanned. Connect the five low current sources to the Model
7058 via the triax connectors.
2. Install the Model 7058 into the Model 705 Scanner main-
frame. Refer to paragraph 2.2.2 for scanner card installation
instructions.
3.
4.
5.
6.
7.
Select appropriate line voltage and turn on the Model 705.
Refer to paragraphs 2.2.1 and 2.3 respectively.
Press 0, 1, FIRST. (Programs channel 1 as the first
channel. 1
To stop the scanning sequence and reset the Model 705 to the
programmed first channel, simply press the RESET button.
NOTE
The output voltages of each thermocouple on the
Model 7057 must be converted to temperature
(OC or OF) using the appropriate thermocouple
tables or polynomial equations, Consult the
Model 7057 Instruction Manual for more informa-
tion concerning the thermocouple tables and/or
polynomial equations,
8.
9.
Press 0, 5, LAST. (Programs channel 5 as the last channel.)
Press INTERVAL, 0, 0, 2, 0, 0, 0, ENTER. (Programs the in-
terval time for two seconds.)
Press CHANNEL, RESET. (Turns on the channel LED,
selects the channel mode for display and resets the Model
705 to the programmed first channel.)
Press SINGLE. (Selects the single scan mode and turns on
the SINGLE LED.)
Press START/STOP. (Initiates the single scan mode and
turns on the START/STOP LED.)
Example 6 Low Current Scan-With the Model 7058 install-
ed, the Model 705 is capable of scanning currents in the range
of picoamps. The Model 7058 is a low current scanner plug-in
card which is field installable in the Model 705 Scanner main-
frame. The card is capable of switching up to 10 channels. The
Model 7058 is designed to introduce a minimum of offset cur-
rent (< IpA), while guarding ensures that high isolation (101%)
is maintained between input signals. Triaxial input and output
connections to the scanner are located at the rear of the card.
Upon actuation of step 9 the Model 705 scans through the pro-
grammed channels at the programmed interval rate one time.
As in the previous examples the scanning sequence can be
stopped at any programmed channel by simply pressing the
START/STOP button. Pressing the START/STOP button
during a scan stops the sequence at the presently displayed
channel, the channel remains closed, and turns off the CHAN-
NEL LED. To resume the scanning sequence from the present-
ly displayed channel, press the START/STOP button. The
START/STOP LED turns on when resuming the scan.
The actual measurement of the low current should be done
with a high quality electrometer such as the Keithley Model 614
or Model 619. A good quality picoammeter could also be used
such as the Keithley Model 480. All three of these instruments
are capable of measuring in the range of picoamps with high
accuracy. To measure such low currents a number of
measurement parameters must be taken into consideration (in-
put impedance, measurement configuration etc,). While this
example does not attempt to give instructions on measuring
low current, the instruction manual provided with each of
previously mentioned electrometer and picoammeter gives
step by step instructions on how to measure low currents ac-
curately.
To stop the scanning sequence reset the Model 705 to the pro-
grammed first channel, simply press the RESET button.
The interval time programmed into the Model 705 for this ex-
ample was chosen at random. The interval time can easily be
programmed for a much longer or much shorter time. General-
ly, the interval time should be sufficient to allow the measure-
ment to settle. The parameters that dictate how long the
measurement needs to settle include source resistance, input
impedance, measurement configuration etc. Consult the low
current measuring devices's instruction manual for details con-
cerning these measurement parameters.
For detailed information concerning the Model 7058, refer to Example 7 Low Voltage Scan-With the Model 7059 install-
the Model 7058 Instruction Manual, document number
ed, the Model 705 is capable of scanning voltage in the sub-
7058-901-OIA. In this example, the Model 705 will be pro-
millivolt region. The Model 7059 is low voltage plug-in scanner
2-l 1