auto shut off with high negative dc voltages

[pascal88]

I have a circuit that has constant current but the load drops in resistance over time. I need to be able to shut off the circuit once a voltage level drop is reached. The voltage starts at -95vdc and reaches -10vdc when I would like the circuit to shut off. Any ideas would be great appreciated? Thank you!

i attached the current regulating circuit. i need a circuit shutoff circuit.

 

[chuckey]

When you say "shut the circuit off", do you mean open circuit the input voltage or short out the output current?
Frank

 

[pascal88]

What I meant was once a negative voltage is reached, the circuit should perform an action. In this case, I used an op-amp to check the voltage level measure against the reference voltage. The issue was as I changed the reference voltage level on one opamp input, it would effect the measured level on the other input. In other words, the voltage input on the -input effected the +input level. I resolved this feedback issue with a feedback resistor on the -input with a gain of 0.