Hi new user,
Just assembled edu09 find that calibrate fails. Signals displayed but at too great y amplitude. Changing volts/div has no effect. All three voltages are correct. Pins 1,5,2 & 4 of ic1 are floating (a few millivolts varying).
Any thoughts please.
The calibration is only to eliminate the offset voltage of the input amplifier section.
Calibration does not affect the gain.
Please check carefully the input voltage divider resistor values.
The voltage at pins 1,5,2 & 4 of IC1 should be proportional to the voltage divider resistor ratio.
E.g. when the input voltage is 10V DC the voltage at pin 1 of IC1 should be:
10V*(15+7.5+1.5+1)/(75+15+7.5+1.5+1) = 2.5V DC
If OK, then please check all resistor values around IC2.
Hi thanks for prompt reply, the culprit was r16 1k5, all working ok now. Pleased with product, good for my purpose.
Regards
J