Yokogawa NFAP135-S50 Pulse Input Module

Overview

The NFAP135-S50 is an 8-channel isolated pulse input module developed by Yokogawa for use in CENTUM VP and ProSafe-RS control platforms. It is engineered to reliably capture high-speed pulse and contact signals from field devices while maintaining strong electrical isolation and signal integrity in electrically noisy environments.

This module supports both 2-wire and 3-wire pulse sources and can directly supply power to compatible transmitters, making it well suited for flow measurement, rotational speed detection, and frequency-based instrumentation.

Key Functional Characteristics

The NFAP135-S50 provides eight fully independent pulse input channels, each electrically isolated from the others and from the system backplane. This architecture prevents signal interference, ground loops, and cross-channel noise, ensuring accurate pulse counting and frequency measurement.

The module accepts a wide range of industrial pulse formats, including dry contact signals, voltage pulses, and current pulses. High-frequency input capability allows it to handle fast-changing signals commonly produced by turbine flowmeters and speed sensors.

Supported Input Signal Types

The NFAP135-S50 accommodates multiple field wiring configurations:

2-wire inputs
Contact ON/OFF signals
Voltage pulse signals
Current pulse signals
Built-in transmitter power supply support

3-wire inputs
Externally powered voltage pulse transmitters

This flexibility allows direct connection to a broad range of field instruments without additional interface hardware.

Performance Specifications

The module is designed for precise pulse acquisition across a wide operating range.

Input frequency range
Up to 10 kHz, depending on signal characteristics and system configuration

Channel isolation
Electrical isolation between all input channels
Isolation between field inputs and system bus circuitry

Counting and measurement functions
Pulse counting
Frequency measurement
Totalizing applications

Mechanical and Environmental Data

Compact construction allows efficient use of cabinet space while maintaining robustness for industrial environments.

Dimensions
32.8 × 107.5 × 130 mm

Weight
0.3 kg

Typical Application Scenarios

The NFAP135-S50 is commonly deployed in process and factory automation systems where accurate pulse acquisition is critical.

Flowmeters with pulse outputs
Turbine and magnetic flow measurement
Motor and shaft speed monitoring
Rotational encoders
High-speed counters and totalizers
Frequency-based instrumentation

FAQ

What distinguishes the NFAP135-S50 from standard digital input modules?

Unlike standard DI modules, the NFAP135-S50 supports high-frequency pulse signals and provides per-channel isolation, enabling accurate counting and frequency measurement without signal degradation.

Can this module power field transmitters directly?

Yes. For supported 2-wire pulse transmitters, the module can supply operating power, reducing the need for external power sources.

Is the module suitable for safety-related systems?

The NFAP135-S50 is compatible with Yokogawa safety and control platforms when used according to system design and certification requirements.