Introduction: For an automated inspection fixture, the key question is whether a single-axis DRO can latch the exact axis position the instant a probe or foot switch fires.
A stationary fixture usually inspects by stopping the axis, waiting for the readout to settle, and then reading a number. That sequence adds a deceleration ramp, a settling window, and a restart to every cycle. The value recorded belongs to where the stage ended up, not where the part was when the probe touched it. Engineers building non-standard inspection stations usually want the opposite: keep the axis moving, capture position on the trigger edge, and send the value straight to the host controller. Probe latching, a foot switch input, and two digital outputs in one embedded readout can support that approach. The timing question is whether the readout, fixture, and host handshake can keep up with the inspection cycle.
The stop-and-read habit comes from manual measuring stations, where an operator moves the axis, stops it, waits for the display to settle, and writes down the number. In an automated fixture, that habit costs real cycle time because every stop adds a deceleration ramp, a settling delay, and a restart before the next feature can be checked. Worse, the number you end up reading describes where the axis came to rest, not where the part surface was at the moment of contact. On a fixture checking shoulder height, step depth, or bore position, that gap is the measurement. Stopping the axis also gives thermal drift and servo hunting time to move the stage after the touch, which can widen the spread between readings. Latching captures the counter value on the trigger edge. A contact probe or foot switch fires, the readout freezes the position that was valid at that instant, and the axis can keep moving or stop on its own schedule without changing the captured number. The only timing that matters is the gap between the physical event and the captured value. At 10 mm/s, an axis covers 10 µm in a single millisecond, so a slow, soft latch smears the result. Touch-trigger probing in machine tool metrology follows the same principle: trigger, latch, then transmit.
The ES-19 embedded single-axis readout combines three capture paths in one compact module. A probe latch captures position from a contact trigger while the axis is moving, a foot switch input captures position on a manual command, and two digital outputs hand the latched value to a PLC or fixture controller. Because they are part of one readout module, the inspection cell can use a single position reference instead of stitching together values from different devices.
On the ES-19, probe latching is an optional microsecond-grade circuit that captures the position counter when a contact probe closes. The input stage accepts standard TTL or RS-422 quadrature signals at up to 250 kHz, so the counter is already tracking the axis closely before the trigger arrives. Resolution is selectable at 5 µm, 1 µm, or 0.1 µm depending on the scale and the task, and the DP-20 processor applies linear and non-linear error compensation plus vibration filtering to the live count. The latched number is tied to the trigger event rather than to a later position after the axis has moved farther down the travel.
The second path is manual. One foot switch input latches the current position on demand, which suits a station where an operator seats a part in a nest and wants the readout to hold that seated position without reaching for a keypad. The two digital position outputs then signal the fixture controller so the host can pick up the value at the right point in the sequence. Data leaves the module through USB 2.0, a 3.3V UART, or optional RS232C, and the API documentation shows how a host program reads the latched value and clears it for the next part.
Cycle time is a budget, and the readout’s input bandwidth sets its first limit. The ES-19 counts quadrature edges at up to 250 kHz. With a 1 µm scale, that ceiling corresponds to roughly 250 mm/s of axis travel, often faster than most inspection moves. A 0.1 µm scale produces ten times as many edges per millimetre, so the same bandwidth is reached at one-tenth of the speed. That is still suitable for fine probing moves, but it is worth checking against your fastest traverse. If a fixture rapids the axis past the probe and only slows near contact, remember that the bandwidth limit applies to the rapid, not just to the probing feed. The second half of the budget lives in the host. Latching on the readout side is one thing; getting the value into the fixture software before the next move begins is another. USB 2.0 and UART both work well when the host reads the latched value on an event or interrupt rather than in a slow polling loop, and optional RS232C helps when a serial port is easier to wire into an existing controller. The practical way to settle the question is a bench test with the real fixture wiring, the real scale, and the real host program, because the handshake between the digital outputs and the controller decides how much of the cycle the transfer consumes. Microsecond-grade probe latching is an optional configuration, and final timing depends on fixture wiring, host response, and integration testing. Before you commit, ask a digital readout manufacturer for the I/O specification and API notes; that is the fastest way to see whether the module fits the fixture you are designing.
For a fast position capture fixture, the deciding factors are straightforward: does the readout latch position at the trigger edge, does it offer the input and output paths your controller needs, and can the host read the latched value inside your cycle time? A single-axis DRO with probe latching, one foot switch input, and two digital outputs covers most non-standard inspection stations without adding a separate data acquisition box. Easson publishes the ES-19 resolution options, I/O configuration, and API documentation, and MOQ is one set. Send your axis speed, scale resolution, trigger type, and host interface; as a digital readout system supplier, we can confirm whether the probe latching option and I/O setup suit your fixture.
A：Probe latching captures the position counter the moment a contact probe closes, instead of waiting for the axis to stop and the display to settle. On the ES-19, it is an optional microsecond-grade circuit that works with the same counter used for normal display, so the frozen value matches where the probe touched the surface. The axis can continue moving or decelerate afterward without disturbing the captured number.
A：Yes. The ES-19 includes one foot switch input alongside two digital position outputs, and that input latches the current position on demand. It suits stations where an operator seats a part into a nest or fixture and wants the seated position held without using the keypad. The latched value is then available to the host over USB 2.0, the 3.3V UART, or optional RS232C.
A：The two digital position outputs provide hardware signals between the readout and the fixture controller. When a position is latched—by probe, foot switch, or command—the outputs can signal the PLC or host that a value is ready to read. The controller then reads the latched value through the communication interface and clears it, ready for the next part in the cycle.
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Easson ES-19 Single Axis Embedded Digital Readout Systems for Metrology
