Counter/Timer Functions; Simultaneous Sample And Hold (Ssh) - Omega Engineering OMB-DBK-34A User Manual

•
The post-trigger scan count specifies the number of scans to be collected after the trigger point.
After the trigger, the post-trigger scans will be collected as programmed and then the system will
disarm itself.
•
The trigger source can be a software command, an external TTL input, etc. An analog input
channel on reaching a specified voltage level can be used to trigger the system. (In this mode, an
analog output channel is used to internally set the analog threshold—making it unavailable for other
use.)

Counter/Timer Functions

Counter/timer circuits are used for counting digital events, timing digital pulses, and generating square
waves and pulses. Counter/timer functions are available from the P3 interface.
The table shows the P3 pinout for the 4 counter and 2 timer channels.
• IN - a digital input that increments the counter and provides a timebase for counter operation.
• OUT - an output of digital square waves and pulses.
The counter channels can act as 4 independent 16-bit up-counters.
The timer channels are driven by an internal timebase of 1 MHz which can be divided by
1 to 65535 to obtain output frequencies from 15 Hz to 1 MHz.

Simultaneous Sample and Hold (SSH)

Some applications require every channel in a scan group to be read at the same instant, as opposed to
being read with 10 µs between channels. Acquiring multiple readings at the same instant is accomplished
with Simultaneous Sample and Hold (SSH).
An example of an SSH application is as follows. In the example, a performance analysis of an engine
needs to indicate cylinder pressure and temperature, piston strain and position, valve position, and engine
rpm and vibration—all at the same instant. Simultaneous Sample and Hold (SSH) is a means of obtaining
such instantaneous data on multiple channels while avoiding time-skew problems.
DBK Option Cards and Modules
Counter/Timer Pins on P3
Pin Signal Name Description
15 TMR 0 OUT Timer 0 output
16 TMR 1 OUT Timer 1 output
17 CTR 2 IN Counter 2 input
18 CTR 0 IN Counter 0 input
35 CTR 3 IN Counter 3 input
36 CTR 1 IN Counter 1 input
886995
Signal Management 1-11