AD 590 control circuit

[Kevinand]

not sure where to post this.

My prof for measurment and instrumentation course gae us a hint to a question on the final exam and i was wondering if you guys could help explain how a circuit of this nature would work.

i am trying to use an op amp with positive voltage reference to control temperature between and upper setpoint and lower set point (IE hysterisis). to do this i was told to use an op amp, in a cicuit with an AD 590 temperature sensor. can comone explain simply how this would work? how the voltage divider is used as the hysterisis of the system.

To be more sepecific he said to control temperature between 17 and 22 degrees C

appreciate any clarification you can provide!

thanks

[johnsold]

This is a much more specific question.

I presume you are largely clueless when it comes to analyzing or designing circuits, because the circuit you posted with the AD 590 and AD 581 is pretty straightforward.  It has no hysteresis.  It also will not work.

The AD590 has an output current of 1 uA/K.  So you can calculate the voltage at the LM 311, pin 3. Assume you have selected RH, RL, and Rset for a setpoint of 20 degrees C and that the current temperature is 15 degrees C.  Now calculate the voltage across RB and determine whether current is flowing through the heater.

Lynn