The TTL converter module is a signal conditioning module which converts an analog signal into a TTL pulse. It is typically used to convert the signal from a blade passage into a TTL pulse.
The module has 2 identical circuits. Each circuit takes an analog voltage input via a BNC connector and converts the signal to a TTL square wave based on a simple voltage threshold. Output is through a BNC connector.
Application #1: Speed Measurement
Converting blade passage into a TTL pulse is an easy way to make a speed measurement system for a bladed rotor. By knowing the number of blades on the rotor, counting blades allows accurate speed measurement. A whole blade speed system consists of an optical probe, an SIU module, and a TTL module. The output of the TTL module can be plugged into a counter card.
Application #2: Once-Per-Revolution (OPR) Signal
Once-per-rev signals are typically in the form of TTL pulses. The TTL card enables the use of an optical probe and an SIU module as a once-per-rev signal by converting an optical signal into a clean square TTL signal.
Application #3: Compatibility With Legacy Blade Tip Timing Systems
Many legacy systems function with a TTL signal out of the sensor interface unit which is sent to a timing card in the data acquisition system. While these systems do not allow precise control of the triggering points as can be done with our sensor interface unit, some customers still use them.
Prime Photonics provides a signal conditioning box for converting analog voltage signals of the entire waveform to a TTL pulse. This box connects to the output of the SIU, converts the waveform into a pulse, and outputs that pulse in a format compatible with a timing card on a legacy data acquisition computer.