Truncate Exponential decay pulse

[ellendort]

RC Circuit assume RC(400ohms*25mfd) is constant and fixed which gives
10msec

How can i truncate the pulse according to the preset time.
In the other word i will be able to control the time from 0-10msec
according to users preset value
without changing the RC.

One way of doing this is by cascading high voltage switches in parallel
to the load sample so as
the CPU will trigger the switch according to users preset value.
For example:
User preset value 7msec
Therefore first 7msec pulse will be on the load sample then the CPU
will trigger the parallel
cascaded switches as the rest of the 3msec pulses will be dissipated on
the high voltage switches.

I'm wondering if there's any other way of doing this? I mean any way to
control this time 0 -
10msec?

Please advice.

 

[Tim Williams]

Well, replace the R with a programmed CCS, tack on a DAC for control.

Tim

 

[Phil Hobbs]

RC Circuit assume RC(400ohms*25mfd) is constant and fixed which gives
10msec

How can i truncate the pulse according to the preset time.
In the other word i will be able to control the time from 0-10msec
according to users preset value
without changing the RC.

One way of doing this is by cascading high voltage switches in parallel
to the load sample so as
the CPU will trigger the switch according to users preset value.
For example:
User preset value 7msec
Therefore first 7msec pulse will be on the load sample then the CPU
will trigger the parallel
cascaded switches as the rest of the 3msec pulses will be dissipated on
the high voltage switches.

I'm wondering if there's any other way of doing this? I mean any way to
control this time 0 -
10msec?

Please advice.

One good method is to reverse the sign of the time coordinate and use an
appropriately-gapped spark plug to cut off the pulse when it gets to the
desired voltage. Google for "Zaphod Beeblebrox the fourth".

Failing that, you could do two things:

1. Tell us what the problem you're trying to solve is, and
2. Either make it funny or show that it isn't homework.

Cheers,

Phil Hobbs

 

[Jim Thompson]

RC Circuit assume RC(400ohms*25mfd) is constant and fixed which gives
10msec
[snip]

I'm wondering if there's any other way of doing this? I mean any way to
control this time 0 -
10msec?

Yes ;-)

...Jim Thompson

 

[Ken Smith]

One good method is to reverse the sign of the time coordinate and use an
appropriately-gapped spark plug to cut off the pulse when it gets to the
desired voltage. Google for "Zaphod Beeblebrox the fourth".

The sign of "t" is a lot harder to reverse than the sign of "R". He could
use a -RC. At t=0, he would put a known charge onto C and then wait for
the current pulse on the gap.

 

[ellendort]

I need to apply a constant voltage pulse on my resistive load in msec.
The time for the pulse varies 0.2-10msec as to my resistive sample
loads
-(2000-5000)ohms
-(20-200)ohms


Pls advice