Question: I have DMM which is producing pulse with duration of around few microseconds. The pulse need to be sampled in PLC, which has sampling rate of 1ms. In other words the cycle loop can't be reduced to microsecond resolution. So it's impossible to reliably detect the pulse from DMM.

Could somebody recommend a simple TTL based circuit solution, which will be able to capture that microsecond resolution pulse and convert it into millisecond resolution pulse?

[![I](https://i.stack.imgur.com/orsZq.png)](https://i.stack.imgur.com/orsZq.png)

Answer: 
TTL solution with active low input and output. R and C are calculated for 2ms output pulse width.

![schematic](https://i.stack.imgur.com/BL5ef.png)

[simulate this circuit](/plugins/schematics?image=http%3a%2f%2fi.stack.imgur.com%2fBL5ef.png) – Schematic created using [CircuitLab](https://www.circuitlab.com/)
Here's an example using a 555 timer in monostable mode. R1 and C1 form the timing network that control the output pulse duration, the output pulse will be \$t\_{pulse}=1.1RC\$ . R3 is a load resistor to make the simulation work, that would be your PLC in this case, and CLK1+NOT1 are the signal source (10Hz with a 1us duty cycle) which in this case is your meter. C2 is for stability, it decouples the internal divider reference ladder somewhat.

![schematic](https://i.stack.imgur.com/EqGpH.png)

[simulate this circuit](/plugins/schematics?image=http%3a%2f%2fi.stack.imgur.com%2fEqGpH.png) – Schematic created using [CircuitLab](https://www.circuitlab.com/)

Here is a plot of the waveforms from this simulation:

[![input waveform from monostable 555 cct](https://i.stack.imgur.com/cwSAZ.png)](https://i.stack.imgur.com/cwSAZ.png)

[![output wavefrom from monostable 555 cct](https://i.stack.imgur.com/n7jSe.png)](https://i.stack.imgur.com/n7jSe.png)

For reference I pulled the design from this website, which goes into far greater detail about the operation of the timer itself:

<https://www.electronics-tutorials.ws/waveforms/555_timer.html>