Input module
AssigneeModicon, Inc.
InventorJerard I. Herman
Life of this patent
Estimating the term…
Abstract
An improved input module is able to sense the ON and OFF states associated with an external signal, wherein that signal complies with standards denoting the ON and OFF condition thereof. The improved input module includes a fixed impedance and a parameter sensor, such as a voltage sensor, which senses at least a portion of the voltage drop across the impedance. In addition, the module includes a current limiter in series with the impedance so as to limit the current flow through the impedance when the threshold parameter has been exceeded. An additional embodiment of the input module includes a second current limiter which is able to selectively detect broken wires associated with the connection of the external signal to the input module.
Claims14
An improved input module for sensing the ON and OFF states of an external signal comprising:
- A) input means for receipt of the external signal;
- B) means for sensing a parameter of the external signal,so as to generate an ON output signal if a threshold of said parameter is exceeded and for generating an OFF output signal otherwise;
- C) input impedance means effectively electrically connected across said input means;
- and
- D) current limiting means connected to the input impedance means so as to limit the current flow through said input means when said parameter is greater than said threshold.
An improved input module for sensing the ON and OFF states of an external signal which for a direct current signal has an OFF voltage level of -3 VDC to 5 VDC, and OFF current level of 0 to 30 milliamps, an ON voltage level of 11 to 30 VDC, and an ON current level of 6 milliamps to 30 milliamps, comprising:
- A) input means for receipt of the external signal;
- B) impedance means connected at one end to said input means;
- C) current limiting means connected at one end to the input means and to second end of the impedance means, for limiting the current flow through the impedance means after the ON threshold voltage is exceeded;
- and
- D) means for sending the voltage across at least a portion of the impedance means so as to generate an ON output signal if the ON threshold voltage is exceeded and an OFF output signal otherwise.
An improved input module for detecting the ON and OFF states of an external signal based upon the external signal respectively exceeding or not exceeding an ON threshold voltage, comprising:
- A) input means for receipt of the external signal;
- B) first impedance means (Z.sub.in) connected at one end to the input means;
- C) second impedance means (Z.sub.sense) connected at one end to the second end of the first impedance means;
- D) first current limiting means connected to the second end of the second impedance means for limiting the current flow through the second impedance means;
- E) means for sensing the voltage across at least the second impedance means so as to generate an ON output signal if the voltage across the second impedance means is indicative of the ON threshold voltage being exceeded and generating an OFF output signal otherwise;
- F) second current limiting means connected to the voltage sensing means for limiting current flow through the voltage sensing means;
- and
- G) means for selectively inhibiting the first current limiting means so as to effectively prevent current flow through the second impedance means, thereby causing at least most current flow passing through the first impedance means to pass through the voltage sensing means so as to allow said voltage sensing means to generate an ON type signal when the input voltage is less than the ON threshold value provided that the external signal is able to generate current flow through the first impedance means;
- whereby the generation of the ON type signal by the voltage sensing means when the first current means is inhibited is indicative of no broken wires connected to the input means and failure to generate the ON type signal under such circumstances is indicative of at least one broken wire to the input means from the external signal.
A method of detecting the ON and OFF states of a signal, comprising the steps of:
- 1) sensing a parameter of the signal so as to generate an ON output signal if a threshold of said parameter is exceeded and for generating an OFF output signal otherwise;
- 2) providing a fixed impedance to the signal so that the current flow through said fixed impedance is substantially proportional to the voltage of the signal;
- and
- 3) further limiting the current flow through the fixed impedance if the signal threshold is exceeded by at least some amount.
Dependencies are inferred from the claim text.