Keithley 2308, Руководство пользователя

Страница: 88 / 226

4-4 Return to Section Topics 2308-900-01 Rev. A / July 2008
Section 4: Long Integration Measurements Model 2308 Portable Device Battery/Charger Simulator User’s Manual
The charger channel has only one trigger level setting for the 5 A current range: 0 A to 5 A. The
battery channel (#1) has four trigger level settings (one for each one of the current ranges: 5 A,
500 mA, 50 mA, or 5 mA). For the 5 A current range, the trigger level may be set from 0 A to 5 A.
For the 500 mA current range, the trigger level may be set from 0 mA to 500 mA.
Similarly
, the
level setting may be set from 0 mA to 50 mA for the 50 mA current range and from 0 to 5 mA for
the 5 mA current range. These settings affect trigger level resolution and are only used when the
corresponding current range is selected. The trigger level setting option on the battery channel
allows you to set a trigger level with greater resolution.
Pulse timeout
TOUT (timeout) specifies the timeout length for the pulse. When the TOUT value is reached, “NO
PULSE” is displayed (top line of the front-panel display). Set the value for TOUT as follows:
TOUT = LINT TIME + x
where x makes TOUT > LINT TIME
TOUT = timeout (time allowed for detection of a pulse)
LINT TIME = long integration time (time allowed for reading after pulse occurs)
For example, if the trigger edge is set to rising, the timeout value should be set to allow sufficient
time for detection of the pulse if the rising edge is just missed. In
Figure 4-2 , point (A) is the point
where we start looking for the pulse. Since the rising edge was just missed, point (B) will be the
first detectable rising edge. If the timeout is less than long integration time, a pulse trigger time out
(due to TOUT) may occur. Therefore, if long integration time = 1.8 seconds, a good TOUT value
would be 2 seconds. A similar method for selecting a TOUT value would be to use a value equal to
105% of the expected pulse period.
Summarizing Figure 4-2 :
1. Reading begins searching for high pulse at point (A).
2. Earliest pulse detected at point (B).
3. Reading time equals Long integration time.