Automatic contrast meter


Posted on Aug 17, 2012

The circuit arrangement consists of a photo-amplifier which feeds a voltage derived from varying light levels in an enlarger to a pair of peak detectors. One follows the peak positive voltage and the other the peak negative voltage. The capacitors used for storing the voltage peaks in the followers also form part of sample and hold circuits which are then switched to hold after the measurement. Their outputs represent the maximum and minimum values of light intensity


Automatic contrast meter
Click here to download the full size of the above Circuit.

A differential amplifier then computes the ratio of these values, and the result is displayed on an LED bargraph meter.




Leave Comment

characters left:

New Circuits

.

 


Popular Circuits

Stereo Audio Amplifier 2x2W or mono 5W ( TEA2025 )
Acid rain monitor
80W-3-30mhz-amplifier
Digital Miscellaneous Temperature Gauge
Logic Probe With Sound
Digital DC Motor Speed Control With LED Display
UHF Indicator - Wavemeter
Vacuum-Tube Voltmeters
Factory secondary low-voltage distribution electrical panel wiring diagram



Top