AAM21-S2 Yokogawa Thermocouple and RTD Input Module

The Yokogawa AAM21-S2 is an analog input module designed to measure low-level voltage signals, thermocouple outputs, resistance temperature sensor (RTS) signals, and three-wire potentiometer inputs. It accepts configurable input types and ranges, allowing temperature and resistance measurements to be processed by the control system. The module provides a 100 ms data update period, input signal isolation between systems, and selectable burnout detection for supported inputs.

Technical Specifications

Input Configuration and Measurement

The module supports several sensor types, but each input must be configured for the connected signal. Thermocouples generate millivolt-level signals, while Pt100 and JPt100 sensors use resistance changes to represent temperature. A three-wire potentiometer provides a resistance-based position or displacement signal, subject to the specified resistance and span conditions.

For thermocouple measurements, reference junction compensation is required. The manufacturer specifies a temperature compensation module for each thermocouple input channel. Type B thermocouples do not receive temperature compensation through this function.

Wiring and Signal Handling

The module installs in an AMN11 analog I/O module nest and connects through M4 screw terminals. For three-wire RTS measurements, the wiring resistance of terminals A and C must match; the specified wiring-resistance effect is limited to +/-40 milliohm at 10 ohm wiring resistance.

The input signals are isolated between systems, with a withstand rating of 1500 V AC for one minute. The auxiliary 1 to 5 V DC output shares its signal ground with the system, so it should not be treated as an independently isolated output.

Burnout Detection and Operating Limits

Burnout detection can be set to UP, DOWN, or OFF, with detection occurring within 60 seconds. When the module is used with a Zener barrier or similar device, the burnout function should be disabled if the barrier impedance and burnout current could cause measurement errors.

For potentiometer measurements, the total resistance can be combined up to 30000 ohm, but guaranteed input conversion requires a total resistance of 100 to 2000 ohm and a measurement span of at least 50% of the total resistance.

Frequently Asked Questions

Q: Which sensors can the AAM21-S2 accept?

A: It supports mV signals, the listed thermocouple types, three-wire JPt100 or Pt100 resistance temperature sensors, and three-wire potentiometers. The input type and range must be selected through software configuration.

Q: Does the AAM21-S2 provide thermocouple reference junction compensation?

A: Thermocouple measurement requires a temperature compensation module for each input channel. Type B thermocouples do not receive temperature compensation through this function.

Q: What should be checked before replacing an existing module?

A: Verify the full model designation, including the S2 suffix, the installed AMN11 nest, the configured sensor type, and the required compensation hardware. Confirm the existing system configuration before selecting a replacement.