Keysight / Agilent / HP E1538A Enhanced Frequency / Totalize / PWM SCP

The Keysight E1538A is an eight-channel Signal Conditioning Plug-On module for VXI systems that independently configures each channel for input or output functions. This non-isolated module delivers flexible digital I/O, frequency measurement, pulse timing, motor control, and sensor interface capabilities in a compact form factor.

Technical Specifications Channels & Configuration

8 channels, non-isolated with variable input level

Each channel independently configurable for input or output Input Functions

Static digital state measurement

Frequency measurement up to 100 kHz

Totalize: positive or negative transitions, 24-bit capacity (16,777,215 counts maximum)

Pulse width measurement: logical 1 widths from 1.5 µs to 1 s

Rotational velocity (RPM) measurement with variable reluctance sensors

Quadrature counting: uses two channels, supports 24-bit counts from 0 to 16,777,215

Low-level sensor inputs: two channels compatible with magnetic pickup or variable reluctance sensors Input Voltage Range

Direct sensing: 100 mV to 10 V

Extended range: up to 120 V with external resistor

Programmable threshold comparator: -48 V to +47 V Output Functions

Static digital state

Single pulse per trigger

Pulse width modulation (PWM): square wave or variable pulse width

Frequency modulation (FM)

Angular position pulse

Stepper motor control: 2- or 4-phase, full- or half-step modes, direct drive up to 100 mA per phase Output Characteristics

Open-drain MOSFET outputs: 0 V to 48 V switching

Sink capability: 100 mA maximum

Programmable output polarity

Configurable pull-up: 380 mA @ 1.2 V (on) or 0 mA (off)

Logic 1 voltage: 0 V (pull-up off) or 5 V no-load (pull-up on)

Logic 0 voltage: 0.1 V max @ 100 mA load (pull-up off) or 0.1 V max @ 100 mA (pull-up on) Frequency Counter & Timing

Gate time (aperture): 1 ms to 1 s, resolution of 1/fin

Square wave output range: 64 Hz to 40 kHz

Pulse width measurement periods: 1 to 255 averaged

Pulse source output: 7.87 µs to 1/f - 7.87 µs width

Key Features

Flexible eight-channel architecture supports simultaneous input and output operations

High-impedance sensor interfaces for magnetic pickup and variable reluctance applications

Direct stepper motor drive capability with external amplifier option for higher currents

24-bit totalize and quadrature counting for precision measurement applications

Programmable digital thresholds spanning ±48 V range

Typical Applications

Motor speed and position control in automated test environments

Pulse and frequency measurement in industrial instrumentation

Sensor signal conditioning for magnetic pickup and variable reluctance transducers

Digital event counting and rotational velocity measurement

PWM signal generation and frequency modulation in system-level testing

Compatibility & Integration Designed as a Signal Conditioning Plug-on (SCP) module for VXI instrument systems, enabling integration into modular measurement platforms requiring mixed-signal I/O and motor control functionality.