Installing a Part-Count Proximity Sensor with Sealevel 170POE-ROHS

Overview

The Sealevel 170POE-ROHS provides two optically isolated digital inputs designed for dry-contact or NPN (sinking) proximity sensors. When powered by PoE, its inputs remain fully isolated from both the Ethernet and machine electrical systems, ensuring safe operation and reliable pulse counting for part detection.

This setup enables accurate part-count data collection directly from machines, improving production tracking and downtime analysis in MachineMetrics.

Feature Availability

How It Works

The 170POE-ROHS sources a small internal current (~12 mA max) through a 330 Ω resistor to each input.
When a proximity sensor detects a part, it sinks the black wire (signal) to ground, allowing current to flow through the opto-isolator. The input registers ON for the duration of the pulse, which MachineMetrics counts as one completed cycle or part.

⚠️ Electrical Isolation: The device provides 1000 V DC optical isolation between inputs and PoE power. It is safe to connect the machine’s 0 V line to the Input Common even when PoE-powered.
⚠️ Do not bond the machine ground to Ethernet or PoE ground — isolation provides the required protection.

How to Use It

Hardware Requirements

• Sealevel 170POE-ROHS

• NPN 3-wire proximity sensor (12–24 VDC)

• Shielded 3-conductor sensor cable

• Existing 12–24 VDC machine power supply

Wiring Instructions (PoE Model)

⚠️ Note: For PoE-powered systems, the Input Common is isolated from PoE ground.
Connecting the sensor’s 0 V (blue) lead to Input Common provides the required reference path without coupling the machine ground to the Ethernet system.

Example Diagram (PoE-Powered)

+24V ───── Brown ───────────────┐
 │
 [Sensor]
 │
Black ──→ Input 1 ◄───┘
Blue  ──→ Input Common ◄───────────── Machine 0 V

Verification Steps

• Apply power to the machine or press and ensure the proximity sensor’s LED operates normally.

• In MachineMetrics, confirm that Input 1 toggles with each part stroke.

• If no count is detected:

  • Verify the blue wire is tied to Input Common.

  • Confirm the black output switches cleanly to 0 V when triggered.

⚠️ If the sensor LED does not light: check for reversed polarity or an open 0 V connection.

MachineMetrics Configuration

Map the input channel as a Modbus device in MachineMetrics.
Each input channel can typically support part-count rates up to several hundred Hz.

Sample Modbus Script

version: 2
unit-id: 1
scan-interval: 0.1
coils:
  part_count_input: 
    address: 1 
    func: 2
variables:
  part_count:
    - source: part_count_input
    - rising-edge
    - count
data-items:
  - part_count

⚠️ Reminder: Confirm that the configured Modbus address matches the input channel you wired (e.g., Input 1 = Address 1).

Tips & Best Practices

• Use shielded sensor cable in electrically noisy environments to avoid false pulses.

• Keep cable runs short and grounded at one end only.

• Verify the sensor’s LED operation before configuring MachineMetrics.

• ⚠️ Never tie machine ground to PoE ground.

• If counts are inconsistent, inspect for loose wiring or electrical noise (EMI).

• Use the shortest possible wiring route between the 170POE-ROHS and the sensor to minimize interference.

FAQs & Troubleshooting

• Q: The counter isn’t incrementing — what should I check?
  A: Confirm the blue wire is connected to Input Common and that the black lead toggles between high and low voltage when triggered.

• Q: Can I connect multiple sensors?
  A: Yes. The 170POE-ROHS provides two isolated inputs; each can be used for a separate sensor.

• Q: Is this compatible with other Sealevel I/O modules?
  A: Yes. The same wiring and configuration principles apply to other Sealevel devices with isolated inputs.

Related Articles

• Sealevel 170POE Overview

• Sealevel 170POE — IP Configuration & Factory Reset Guide

• How to Install a Current Transducer

• Adding a New Machine to Your Account