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.
