I am trying to create a one-shot using an NE556 timer IC. The circuit I have devised is shown in the first attachment to this message. There is nothing special about it. I just followed the directions in the data sheet. At the input is an RC differentiator (R2-C3) that I found out is required, since the NE556 one-shot will not terminate while the input is left low. The timing RC pair (R1-C1) is a 100K resistor and a .47 uF capacitor. According to the literature I read, the time constant should equal 47 mSec, which is how long the one-shot should last each time it is triggered. However, when I put a scope on the signal (see second attachment), the one-shot lasts only 1.5 mSec. Note that the oscilloscope trace shows the input after differentiation (the red trace) and the output (yellow trace).
I have computed the time constant several times and each time I get 47 mSec. I feared bring up this question, because I was worried that I am making some really stupied error. However, my frustration finally triumphed and hence this post. If someone with experience with the NE556 could help, that would be greatly appreciated.