Measurement Computing

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USB-CTR Series

Features

Synchronous Counter and Digital

Inputs

USB-CTR Series devices can and read digital and counter inputs

simultaneously at the supported data streaming rates (refer to

Counter I/O and Gating).

Timer Output

USB-CTR Series devices have four 32-bit timer outputs. Each

timer can generate a programmable width pulse with a software-

selectable frequency in the range of 0.02235 Hz to 48 MHz. At

higher frequencies, the timer output frequency and duty cycle

depend on the load impedance and the supply.

The timer output rate and pulse width can be updated asynchro-

nously at any time; however, doing so results in a pulse stream

that is not seamless.

The following timer output options are software-selectable:

• pulse frequency

• duty cycle (pulse width divided by the pulse period)

• number of pulses to generate

• time delay before starting the timer output after it’s

enabled

• resting state of the output (idle high or idle low)

Both the period and time delay ranges are 20.83 ns to 44.739 sec-

onds.

Timer

Generator

+5 V

TMRx Terminal

USB-CTR Series PWM timer channel

Trigger Input

USB-CTR Series devices can trigger synchronous acquisitions of

counter data internally with software or externally using the

digital trigger input connector.

The digital trigger input allows TTL-level triggering with laten-

cies guaranteed to be less than 20.83 ns. The acquisition can be

triggered on a rising or falling edge, or on a high or low level.

The trigger input is TTL logic. Latency is one sample period,

maximum. The input signal range is –0.5 V to 5.5 V maximum.

The logic level (1 or 0) and the rising or falling edge for the

discrete trigger input are software-selectable.

When using the external trigger, the counter begins counting

when the scan starts, even though acquisition of the count is

held off by the trigger. To coordinate the start of the acquisition

with the start of the count, you could use the trigger signal to

also trigger the gate of the counter in use. Clearing the counter

before starting the scan re-arms the gate trigger.

External Clock Pacing

You can pace synchronous acquisition of counter data by the

onboard clock or by an external clock connected to the external

clock input connector.

Power Output

Use the

+VO connector to supply power to external devices or

circuitry.

The maximum total output current that can be drawn from all

USB-CTR Series device connections (counter outputs, timer out-

puts, digital outputs, pacer clock output, and

+VO) is 240 mA.

This maximum applies to most personal computers and self-

powered USB hubs. Bus-powered hubs and notebook computers

may limit the maximum available output current to 100 mA.

If the device requires current that exceeds the current available

from the computer, connect the device to a self-powered hub or

power the computer with an external power adapter.

USB-CTR Series OEM Versions

OEM versions have board-only form factors with header con-

nectors for OEM and embedded applications. All devices can be

further customized to meet customer needs.

The OEM versions have the same specifications as the standard

devices, but come in a board-only form factor with header connectors

instead of screw terminals.