Counting with Counters

Counting with Counters on the TMX Data Acquisition Recorder

The ability to record the frequency of a signal or count a period of a waveform is an important feature for a data acquisition recorder. These signal inputs include rotary encoders, linear encoders, switches and other signals where an on/off pattern must be recognized. Examples include frequency, tachometer and distance measuring functions. Monitoring and recording these signals is useful for a wide variety of applications including:

• Measuring the rotation angle on a radar antenna
• Monitoring the moving parts of a robotic welder
• Troubleshooting manufacturing pick-and-place machinery used in food processing
• Troubleshooting the servo motor on a rotational knife system
• Measuring the distance of a borehole for drilling inspection equipment
• Counting and totalizing switches for industrial processes

The simplest form of counting functionality on the TMX, TMX-18 and Dash MX allows for frequency to be converted by measuring the time of a single period of an input waveform and then taking the reciprocal of that number. For input signal pulse trains that are derived from a moving component (rotary or linear) on an instrumented machine, the TMX, TMX-18 and Dash MX user units facility can be used to convert to engineering units such as revolutions per minute (RPM), feet, or the like. Other forms of counting include pulse width detection, duty cycle detection, period detection, edge separation time detection, incremental pulse event counting (totalizing from interrupted light beams, limit switches, gate switches, etc.) and quadrature event counting (up/down counting from an optical rotary or linear encoder).

TMX Input Modules with Counter Capability

UNIV-6 — Frequency, Duty Cycle, Pulse Width, Event Counter and Period Detection
IHVM-6 — Frequency, Duty Cycle, Pulse Width, Event Counter and Period Detection
IBRM-6 — Frequency, Duty Cycle, Pulse Width, Event Counter and Period Detection
IEPE-6 — Frequency, Duty Cycle, Pulse Width, Event Counter and Period Detection
NIDV-16 — Frequency, Duty Cycle, Pulse Width, Event Counter and Period Detection
DIOC-16 — Frequency, Duty Cycle, Pulse Width, Event Counter, Quadrature (X1, X2 & X4 with and without Z input Reset), Edge Separation, and Period Detection

The TMX is capable of the following counter types:

Frequency (Time Based) — Standard frequency which averages readings over a selected time period and updates based on that same period.
Frequency (Cycle Based) — Frequency counter that updates as fast as once every other cycle of the input waveform yielding the fastest updating counter at the expense of increased output jitter.
Duty Cycle — Percent of time that a rectangular wave input is high.