Filter Configuration - Keithley 2500 User Manual

Models 2500 and 2502 User's Manual
Advanced filter — The Advanced Filter is part of the Moving Filter. With the Advanced
Filter enabled, a user-programmable noise "window" is used with the Moving Filter. The
noise window, which is expressed as a percentage of range (0-105%), allows a faster
response time to large signal step changes. If the readings are within the noise window, the
Moving Filter operates normally as previously explained. If, however, a reading falls out-
side the window, the stack is flushed of old readings and filled with the new reading.
For example, assume the window is set to 10% and the 20mA range is selected. Therefore,
the noise window is ±2mA (20mA × 10% = 2mA). Also assume the first reading is 2mA.
Per normal filter operation, the stack is filled with that reading. As long as each subsequent
reading is within ±2mA of the previous reading, the filter operates normally. Now assume
a 10mA noise spike occurs. This noise window violation causes the stack to flush out the
old readings and fill it with 10mA reading.
NOTE
Filter configuration
Using
NOTE
1. Press the CONFIG key and then the FILTER key to access the filter configuration
menu.
2. Select AVERAGE-MODE, then choose the REPEAT or MOVING filter as required.
3. Place the cursor on AVERAGE-COUNT and press ENTER to display the present aver-
age count for the filter.
4. Use the , , , and
5. Place the cursor on ADVANCED and press ENTER. The blinking cursor will indicate
the state of Advanced Filter.
6. Use the
ABLE or ENABLE), and press ENTER.
7. If you enabled the Advanced Filter, use the , , , and
noise window (0% to 105%) and press ENTER.
8. Place the cursor on MEDIAN RANK and press ENTER to display the present median
rank for the Median Filter.
9. Place the cursor on the desired rank value (0 to 5) and press ENTER. Keep in mind
that a rank of 0 disables the Median Filter.
10. Use the EXIT key to back out of the menu structure.
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If the Repeat or Median Filter is enabled, the Moving Filter operation will not
start until after the previous filter yields a reading. In other words, after a read-
ing is yielded from the Repeat or Median Filter, that reading will then be sent to
the Moving Filter stack.
Table 6-5 and Figure 6-6
The filter setting is global and affects both channels.
keys to display the desired count (1 to 100) and press ENTER.
or key to place the cursor on the desired Advanced Filter selection (DIS-
Range, Digits, Speed, and Filters
as a guide, configure the filter as follows:
6-11
keys to display the desired