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3-28 Pulse Current Measurements

Model 2306 measures them first.) Also set TLEV1 for the initial step. This value needs to be

appropriate for detecting the first DOWN step as an UP step measurement (in Figure 3-9, this

value is set at 750mA). For the UP steps, set the trigger level to a value appropriate for each

sing step. The key to detecting this pulse sequence is setting the step timeout to a value high

enough to bypass the remaining down steps after measuring the first step.

For Figure 3-9, the

following expected measurement values and TLEVs were used:

Expected measurements

UP 450mA, 575mA, and 700mA (4th–6th pulses)

DOWN 900mA, 600mA, 300mA (1st-3rd pulses)

TLEVs (all rising)

TLEV1 750mA (1st pulse) TLEV3 500mA (5th pulse)

TLEV2 400mA (4th pulse) TLEV4 625mA (6th pulse)

This pulse sequence can be measured using the continuous pulse method (see the

programming example “Continuous pulse train” on page 3-34). Similarly, this pulse train could

be measured using the one-shot method. For the one-shot method, the first step trigger level

alue could be any value for detecting the 900 milliamp step.

Timeout setting

TOUT (TimeOUT — timeout setting) specifies the timeout length for detecting a given pulse

step. When the TOUT value is reached, an overflow value for that step reading is returned.

Although all step measurements after the first TOUT step are returned as overflow readings, all

step measurements performed before TOUT was exceeded will have correct readings.

Two timeout settings are used: one for the initial step and another for the rest of the active

ste

ps. The setting for the initial timeout should be set slightly longer than the period of the pulse

for continuous pulse trains. The other timeout setting should cover the longest step duration.

Also, make sure to account for trigger delays when determining timeout settings. There are two

possible trigger delays: the internal trigger delay (15µsec necessary for code execution), and any

user specified trigger delay (optional). The trigger delays occur before the integration process

begins but after pulse detection.

To use the pulse current step method to measure a one-shot pulse train, set the initial timeout

to th

e maximum setting of 60 seconds. This allows the Model 2306 to be triggered for step

measurements, then a few seconds of delay before generating the one-shot pulse train. The few

seconds of delay are required to ensure the Model 2306 is setup and ready to detect the first step

when it happens along with the rest of the steps.

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Keithley 2306 User Manual

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