Counter Inputs; Tips For Making High-Speed Counter Measurements (> 1 Mhz); Mapped Channels - Measurement Computing USB-1616HS-BNC User Manual

USB-1616HS-BNC User's Guide
No pre-trigger, infinite post-trigger
In this mode, no pre-trigger data is acquired. Instead, data is acquired beginning with the trigger event, and is
terminated when you issue a command to halt the acquisition.
Fixed pre-trigger with infinite post-trigger
You set the amount of pre-trigger data to acquire. Then, the system continues to acquire data until the program
issues a command to halt acquisition.

Counter inputs

Four 32-bit counters are built into the USB-1616HS-BNC. Each counter accepts frequency inputs up to 20
MHz.
USB-1616HS-BNC counter channels can be configured as standard counters or as multi-axis quadrature
encoders.
The counters can concurrently monitor time periods, frequencies, pulses, and other event driven incremental
occurrences directly from pulse-generators, limit switches, proximity switches, and magnetic pick-ups.
Counter inputs can be read asynchronously under program control, or synchronously as part of an analog or
digital scan group.
When reading synchronously, all counters are set to zero at the start of an acquisition. When reading
asynchronously, counters may be cleared on each read, count up continually, or count until the 16-bit or 32-bit
limit has been reached. See counter mode explanations below.
Tips for making high-speed counter measurements (> 1 MHz)
 Use coax or twisted-pair wire. Connect one side to Digital Common.
 If the frequency source is tolerant, parallel-terminate the coax or twisted-pair with a 50 Ω or 100 Ω resistor
at the terminal block.
 The amplitude of the driving waveform should be as high as possible without violating the over-voltage
specification.
 To ensure adequate switching, waveforms should swing at least 0 V to 5 V and have a high slew rate.

Mapped channels

A mapped channel is one of four counter input signals that can get multiplexed into a counter module. The
mapped channel can participate with the counter's input signal by gating the counter, latching the counter, and
so on. The four possible choices for the mapped channel are the four counter input signals (post-debounce).
Figure 9. Typical USB-1616HS-BNC counter channel
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Functional Details
DB 37
connector