Functional Overview

The Tektronix 5A18N is a dual-channel vertical amplifier plug-in designed to expand the measurement capabilities of the Tektronix 5100 and 5400 series oscilloscope mainframes. By providing two fully independent vertical channels, it allows users to observe the relationship between two different signals simultaneously. This is particularly useful for measuring phase shifts, comparing input versus output signals in an amplifier circuit, or timing pulses in digital logic gates.

Operating within a 2 MHz bandwidth, the 5A18N is optimized for accuracy in the audio frequency and low-radio frequency (LF) spectrum. It serves as a reliable workhorse for general-purpose electronic testing where high-frequency transients are not the primary concern, but where DC stability and low-level signal amplification are essential. The module's "N" suffix indicates its simplified design, which omits on-screen readout characters in favor of a direct, knob-controlled user interface that emphasizes tactile reliability and immediate feedback.

Technical Specifications

Based on official Tektronix instrumentation standards, the 5A18N follows the specifications below:

Common Mode Rejection At least 10:1 at 2 MHz (in ADD mode with CH 2 inverted)

Core Features and Display Flexibility

Multiple Vertical Operating Modes

The 5A18N provides several ways to view your data, selectable via the front panel pushbuttons:

• ALT (Alternate): Switches between Channel 1 and Channel 2 at the end of each sweep. This is ideal for viewing two signals at faster sweep speeds.

• CHOP (Chopped): Switches between channels at a high internal rate (approx. 100 kHz). This mode is preferred for viewing two slow-moving signals simultaneously to see their real-time relationship.

• ADD (Algebraic Addition): Displays the sum of Channel 1 and Channel 2. When Channel 2 is inverted, this mode provides a differential measurement capability, showing the difference between two signals.

Independent Channel Control

Each channel on the 5A18N features its own Volts/Div selector and position control. The "Variable" knob allows for uncalibrated continuous adjustment between the fixed steps, providing the ability to overlap two signals for visual comparison. Both channels also feature independent AC/DC/GND coupling switches, allowing for the removal of DC offsets when inspecting small AC ripples on high-voltage rails.

Industrial and Laboratory Applications

The 5A18N Dual Trace Amplifier is a staple in diverse technical environments:

• General Electronics Repair: Comparing waveforms in power supplies, audio amplifiers, and consumer electronics.

• Education: Used in university labs to teach students the fundamentals of oscilloscope operation and signal analysis.

• Industrial Control Systems: Monitoring 4-20mA loops and low-frequency PLC outputs to ensure timing and voltage levels are correct.

• Automotive Diagnostics: Analyzing sensor signals such as oxygen sensors and crankshaft position sensors that operate in the kilohertz range.

Installation and Calibration

The 5A18N is a standard plug-in module that slides into any vertical compartment of a Tektronix 5000-series mainframe. For optimal performance, the following steps are recommended:

1. Insertion: Ensure the mainframe is powered off. Slide the module in until the latch snaps. 2. Warm-up: Allow at least 20 minutes for the internal components to reach thermal equilibrium before performing critical measurements. 3. DC Balance: Periodically check the DC balance by switching between sensitivity ranges; if the trace jumps vertically, the internal DC balance adjustment may be required as per the service manual. 4. Probe Compensation: Always perform a probe compensation adjustment when using a 10x probe to ensure a flat frequency response.

Conclusion

The TEKTRONIX 5A18N remains a highly respected and reliable vertical amplifier module for the 5000-series oscilloscope platform. Its dual-trace capability, combined with a user-friendly analog interface and microvolt-level sensitivity, ensures it meets the needs of modern low-frequency signal analysis. Whether used for circuit design, system maintenance, or educational purposes, the 5A18N delivers the precision and signal clarity that has made Tektronix a leader in test and measurement instrumentation for decades.