Low level voltage programmable logic control

A programmable logic control device for monitoring a current of a circuit in a nuclear reactor environment and for activating a circuit control device if the current exceeds a selected level for a selected interval, the programmable logic control device including:

• (a) electrical power means for activating the circuit control device;
• (b) electrical circuitry means including integrated circuitry means for monitoring the current of the circuit, the electrical circuitry means including:
• (i) adjustable electrical signal input circuitry means to match the programmable logic control device to the current;
• (ii) adjustable pick-up circuitry means for adjusting the selected level for the current of the circuit;
• (iii) adjustable time circuitry means for adjusting the selected interval for the selected level for the current so as to command the electrical power means, the selected interval sufficient in duration to minimize nuisance tripping;
• and
• (iv) control means for controlling voltage level applied to the adjustable pick-up circuitry means and time circuitry means substantially without resistive burden, and the control means including spaced first and second thermisters, and only a resistor disposed directly between said first and second thermister and connected directly in series thereto so as to stabilize the voltage level for temperature fluctuations;
• wherein the integrated circuitry means is housed in a material that is resistant to nuclear radiation.

A programmable logic control device for monitoring a current of a circuit and for activating a circuit control device if the current exceeds a selected level for a selected interval, said programmable logic control device comprising:

• (a) electrical power means for activating the circuit control device;
• and
• (b) integrated circuitry means for monitoring the current of the circuit, the integrated circuitry means including:
• (i) control means including a shunt comprising spaced first and second thermistors and only a resistor disposed directly between the first and second thermister and connected directly in series thereto that varies inversely to temperature fluctuations for stabilizing the voltage level for said temperature fluctuations.

A programmable logic control device for monitoring a current of a circuit and for activating a circuit control device if the current exceeds a selected level for a selected interval, said control device comprising:

• (a) electrical power means for activating the circuit control device;
• and
• (b) electrical circuitry means for monitoring the current of the circuit, the electrical circuitry means comprising:
• (i) control means including a spaced first and second thermister, and only a resistor disposed directly between said first and second thermister and connected directly in series thereto.