IO Modules - Inputs and Outputs - Maximizing accuracy in analog signal transmission

Introduction

Analog inputs and outputs in devices like AAC20, IO modules, MAC36NL are sensitive to cable length and type, which can significantly affect measurement accuracy due to resistance and voltage drop. Ensuring optimal cable length is crucial for maintaining the integrity of the transmitted signal.

Good Practice

To optimize the performance and accuracy of analog inputs and outputs in devices such as AAC20, IO modules, MAC36NL, it is essential to consider both the cable type and length. Here are detailed best practices:

1. Choose the Right Cable Size and Type: For analog outputs, a 16 AWG cable is recommended due to its lower resistance of 13.17 Ohm per 1000 meters, which helps in minimizing voltage drops over longer distances.

2. Calculate Maximum Cable Length:

   • For analog outputs, use the formula:

     CODE

     Maximum Length = V_d / (R * n * I)
     V_d - the maximum permissible voltage drop (0.3V for the calculation)
     R - cable resistance
     n - number of receivers - elements controlled by the output
     I - maximum current (typically 20mA)

     For a single receiver and minimal interference, a safe cable length is approximately 100 meters.

   • For analog inputs operating as voltage inputs, a cable length of up to 500 meters is generally safe as resistance doesn’t have big impact on the measurement.

   • For resistance inputs, a length of up to 100 meters for a 16 AWG cable does not significantly impact measurement, considering the use of built-in temperature sensors characteristics and potential offset adjustments to compensate for cable resistance.

3. Consider Environmental Factors: Always account for potential environmental interferences such as electromagnetic disturbances in the installation area, which might necessitate shorter cable lengths or the use of shielded cables.

4. Regular Calibration and Testing: Implement regular checks and calibrations, especially when operating near the recommended maximum lengths to ensure accuracy is maintained over time.