Active input voltage sensing for low voltage analog signal detection

Abstract

An input circuit for detecting low voltage analog signals in an electrically noisy environment receives the analog input signal at an input terminal. The analog input signal is compared to a variable reference signal at a comparator circuit. An active hysteresis circuit provides feedback to the comparator. In a first operating mode, the active hysteresis circuit may be disabled or be configured to output a constant voltage. In a second operating mode, the active hysteresis circuit may be enabled or configured to output a varying level of voltage. The output of the feedback circuit is summed with the variable reference signal and supplied as the input signal to the comparator, such that signal against which the analog input signal is compared is a general constant value in the first operating mode and varies with respect to time in the second operating mode.

Description

BACKGROUND INFORMATION[0001]The subject matter disclosed herein relates to the field of industrial automation, and more specifically, to an input module with active hysteresis and an adjustable reference to detect an analog signal in an electrically noisy environment.[0002]Industrial controllers are specialized computer systems used for the control of industrial processes or machinery, for example, in a factory environment. Generally, an industrial controller executes a stored control program that reads inputs from a variety of sensors associated with the controlled process and machine and, sensing the conditions of the process or machine and based on those inputs and a stored control program, calculates a set of outputs used to control actuators controlling the process or machine.[0003]Industrial controllers differ from conventional computers in a number of ways. Physically, they are constructed to be substantially more robust against shock and damage and to better resist external ...

AI Technical Summary

Benefits of technology

The solution effectively detects low voltage analog signals in noisy environments, expanding the sensor's operating range and reducing complexity and cost by minimizing the number of filters required, while maintaining robustness and precision in controlling industrial machinery.

Problems solved by technology

An electrically noisy environment includes sources of electromagnetic noise that may be radiated and / or conducted between the source of the electromagnetic noise and a circuit located within the environment.

One source of electromagnetic noise may be electric machines.

A sensor operating in this electrically noisy environment may have limitations imposed on its operation as a result of the environment.

In particular, detection of voltage signals having a low magnitude is challenging in such an environment.

As a result, the sensor may not be able to operate across its full sensing range, but rather operate only to a point where the output from the sensor yields a signal-to-noise ratio great enough to distinguish the signal from the noise.

However, additional filtering is commonly required and may require multiple filters such as a low-pass filter, a high-pass filter, a band-pass filter, or a combination thereof.

The differential amplifiers and additional filters require space on the circuit board for each input channel and add cost and complexity to the input module.

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