Shunt calibration for electronic pressure switches

An electronic switch apparatus, comprising:

• a bridge circuit responsive to applied pressure to provide at an output a voltage proportional to applied pressures,
• a control circuit coupled to said bridge for receiving said output voltage and for providing an indication when said voltage exceeds a predetermined value indicative of an improper pressure,
• switching means responsive to said provided indication to operate an indicator capable of notifying a user of said improper pressures,
• an impedance having a first terminal coupled to an output of said bridge and a second terminal, and
• a selectively operated switch having one terminal coupled to said second terminal of said impedance with said other terminal coupled to a reference potential, said switch being operative in a first position to cause said impedance to shunt said bridge to cause said bridge to provide a voltage indicative of said improper pressure during the absence of an applied pressure to said bridge and operative in a second position to isolate said impedance from said bridge whereby a user can determine whether said switching means and indicator will be operative upon application of the applied pressure.

A monitoring system comprising:

• a resistive bridge for providing an output indicative of a sensed condition:
• an indicator being electrically coupled to said bridge and for providing an indication when the sensed condition satisfies a threshold condition;
• and,
• a switch for selectively shunting an electrical impedance into said bridge:
• wherein, said impedance is of a magnitude to cause said bridge output to be indicative of the sensed condition satisfying the threshold condition, regardless of said sensed condition, when shunted into said bridge by said switch, and wherein said threshold condition corresponds to a threshold pressure value.