APD 7500 - DC to Frequency Isolated Transmitter - Field Configurable

The APD 7500 DC to Frequency Isolated Transmitter is a versatile, field-configurable signal conditioning module designed to convert analog DC voltage or current signals into a proportional frequency output. Engineered for industrial automation and process control applications, the APD 7500 enables seamless integration of analog signals into digital systems such as PLCs, counters, totalizers, and data acquisition platforms.

With full 3-way isolation, a wide range of selectable input and output configurations, and robust diagnostic features, the APD 7500 provides a reliable and flexible solution for analog-to-frequency signal conversion.

Convert Analog Signals to Frequency with Precision

The APD 7500 accepts DC voltage or current inputs and converts them into a frequency output that is directly proportional to the input signal.

• Input ranges: 0–50 mV to ±10 VDC, and 0–1 mA to 4–20 mA

• Output ranges: 0–1 Hz up to 0–30 kHz

This conversion is ideal for applications where frequency signals are preferred due to their noise immunity, long-distance transmission capability, and compatibility with digital instrumentation.

Designed for Industrial Automation and Control

The APD 7500 is widely used in industrial environments where analog signals must be converted into frequency for processing or transmission.

Typical applications include:

• Interfacing analog sensors with PLC frequency inputs

• Pulse counting and totalizing systems

• Flow measurement and monitoring systems

• Long-distance signal transmission

• Data acquisition and process control

By converting analog signals into frequency, the APD 7500 ensures reliable signal transmission even in electrically noisy environments.

Wide Range of Field-Selectable Inputs and Outputs

The APD 7500 offers exceptional flexibility with 24 selectable input ranges and 30 selectable output frequency ranges.

Input Options:

• Low-level millivolt signals (0–50 mV)

• Standard voltage signals (0–10 V, ±10 V)

• Industrial current loops (4–20 mA and others)

Output Options:

• Low-frequency ranges for totalizing (0–100 Hz to 0–1500 Hz)

• High-frequency ranges for high-speed systems (0–2 kHz to 0–30 kHz)

These ranges are easily configured using rotary and slide switches, allowing for quick adaptation to a wide range of applications.

Full 3-Way Isolation for Reliable Signal Integrity

The APD 7500 provides full isolation between input, output, and power circuits:

• Isolation rating: 1200 VRMS minimum

This isolation ensures:

• Elimination of ground loops

• Protection of connected equipment

• Improved common-mode noise rejection

• Stable signal transmission in harsh environments

MOSFET or TTL Frequency Output

The APD 7500 features a flexible frequency output that can be configured for different interface requirements.

• MOSFET (open drain) output: requires external pull-up resistor

• TTL output: easily enabled via internal jumper

This allows the module to interface with a wide variety of devices, including PLCs, counters, and digital inputs.

Adjustable Low Frequency Cutout

The APD 7500 includes an adjustable low-frequency cutout feature that disables output below a defined input threshold.

• Adjustable from approximately 2% to 25% of input range

This feature is particularly useful for eliminating false readings caused by noise or low-level signal fluctuations.

Built-In Loop Power for Simplified Wiring

The module includes an integrated loop power supply:

• 13 VDC loop excitation

• Up to 25 mA capacity

This allows the APD 7500 to power passive current loop devices, reducing the need for additional external power supplies.

Sink/Source Input Flexibility

The APD 7500 supports both powered and unpowered current loop inputs.

• Can be wired for sinking or sourcing inputs

• Compatible with a wide range of transmitter configurations

This flexibility simplifies integration into existing systems.

LoopTracker® LEDs for Real-Time Monitoring

The APD 7500 includes API’s exclusive LoopTracker LEDs:

• Green LED indicates input signal level

• Red LED indicates output frequency activity

• LED brightness varies with signal intensity

These indicators provide a quick visual reference for system status and can greatly assist during startup and troubleshooting.

Output Test and Override Function

A built-in test function allows users to simulate an output signal independent of the input.

• Adjustable from 0 to 100% of output span

• Activated via front-panel button or remote contact

This feature simplifies system commissioning and verification.

High Accuracy and Stable Performance

The APD 7500 delivers reliable performance across a wide range of operating conditions:

• Linearity: ±0.4% of span

• Temperature stability: ±0.02% of span per °C

• Response time: ~70 ms typical

These specifications ensure accurate signal conversion and consistent system performance.

Rugged Industrial Design

The APD 7500 is built for demanding industrial environments:

• Operating temperature: –10°C to +60°C

• DIN rail mounting (35 mm standard)

• Compact housing (22.5 mm width)

• Removable terminal blocks for easy installation

Its robust construction ensures long-term reliability in industrial applications.

Flexible Power Options

The APD 7500 supports multiple power configurations:

• 85–265 VAC or 60–300 VDC

• Optional low-voltage version: 9–30 VDC or 10–32 VAC

This flexibility allows the module to be used in a wide range of systems.

Typical Applications

The APD 7500 is ideal for applications requiring analog-to-frequency conversion:

• Flow totalizing and monitoring

• Industrial process control systems

• Signal transmission over long distances

• PLC and SCADA integration

• Pulse-based measurement systems

Why Use a DC to Frequency Transmitter?

Frequency signals offer several advantages over analog signals:

• Greater immunity to electrical noise

• Reliable transmission over long distances

• Compatibility with digital systems

• Improved accuracy in counting and totalizing applications

The APD 7500 provides a reliable way to convert analog signals into frequency for these applications.

Why Choose the APD 7500?

The APD 7500 stands out as a high-performance signal conditioning solution due to its:

• Wide range of input and output configurations

• Field-configurable setup

• Full 3-way isolation

• Flexible MOSFET and TTL outputs

• Built-in loop power supply

• Adjustable cutout functionality

• Diagnostic LEDs and test features

• Rugged industrial design

A Flexible Solution for Analog-to-Frequency Conversion

The APD 7500 DC to Frequency Isolated Transmitter provides a reliable, flexible solution for converting analog signals into frequency outputs. Its combination of configurability, performance, and durability makes it an essential component in modern industrial systems.

Optimize Your Signal Conditioning System

Whether you are integrating sensors into a PLC system, designing a totalizing application, or improving signal reliability, the APD 7500 delivers the performance needed for accurate and dependable operation.

Contact us today to learn more or configure a solution tailored to your application.