Resistance-ratio detector


Posted on Jul 15, 2012

Applications such as photoelectric control, temperature detection and moisture sensing require a circuit that can accurately detect a given resistance ratio. A simple technique that uses an op amp as a sensing element can provide 0,5% accuracy with low parts cost. The reed-relay contacts close when the resistance of the sensor Rp equals 47% of the standard Rs. Adjusting either Rl or R2 provides a variable threshold; the threshold is controlled by varying R3. For the most part, the type of resistors used for Rl and R2 determines the accuracy and stability of the circuit.


Resistance-ratio detector
Click here to download the full size of the above Circuit.

With metal-film resistors, less than 0.5% change in ratio sensing occurs over the commercial temperature range (0 to 70 C) with ac input variations from 105 to 135 V.




Leave Comment

characters left:

New Circuits

.

 


Popular Circuits

Car PC MP3 Player
TRIAC Light Dimmer
High power mobile phone Jammer circuit
Motor Generator Stepper
12W Audio Amplifier Circuit with TDA2006
microphone CAD equitek E100
interface gps with avr
make tv transmitter
LM1881 LM1881 Video Sync Separator



Top