REVERSE DISCRIMINATION

[kt315]

50 or 100uA. use this schema. tune resistors on edge max needle position at both left and right side/sector.

[kt315]

i just ordered the mini oscilloscope kit that you showed...i dont really have extra room in my surf pi housing for extra electronics for another sample circuit...so i will try the oscilloscope method but i will have to get a project box with a transparent window for the scope...not sure if i can a ready made one ???

warning - do not connect a probe of the oscope to a coil, or to DRAIN pin of mosfet, another way you get a trouble. connect on output of preopamp. but better would be
connect to schema i uploaded -- phasevariator + BF245 + opamp, then you get a possibility to choice a optimal point on the decay for the discrim.

[daverave]

can you show me the phasevariator + bf245 + opamp.

[kt315]

marked by red

[daverave]

would i have to add this circuit to my surf pi...or can i just connect mini oscilloscope to the output of the NE 5534 op amp ????

[kt315]

at first connect to output of NE5534. if you do not see a result (no visual lucid disc) then add this circuit. you can take
the similar part from surf PI schema (phasevariator U4C/D/B + BF245 + opamp).
or only add U4D/B, also be connected to U4C and change R28 on a pot, i think ~470k.

[daverave]

ok thanks kt315

[daverave]

Hi kt315
can you tell me approx the timing of the late sample for the circuit schematic that you showed us to get a negative swing on the meter on iron.

[kt315]

hi Dave, not mine matter. alien schematic, alien issue. i am not pole to be in the subj and answer to you.
alien issue always is suspecting full lack of detailed data. this is rule. registered in polish forum to find up something http://www.poszukiwanieskarbow.com/F...4183d17cffce0f
be cause the forum is closed from aliens and no access to threads simply clicking.
NOTHING. as exspected. looks you have to experiment yourself learning a reaction on metal on pocket o-scope screen.

br

[daverave]

i got my mini scope today just got to build it....it only cost £15 uk pounds which is very good value...just got to find a box now with a window for the display...which will not be easy cause of size of pcb...i may build that disc circuit on verro board and experiment as you said.

[kt315]

seaching something on the matter... Having some fun with my brother about metal detecting with pulse induction tecnique. Oscilloscope style displayig of decay curve, time range 14to52 microseconds after pulse-off, not so fast&elegant coil, lots of interferences but it's enought to observe the diff decay curve of gold, copper, alu, iron.
How many opamps do you use for examening the pulse
just 1 good railt-to-rail opamp without too much gain

[kt315]

[kt315]

[daverave]

Hi kt315
did this person use the output of the ne 5534 op amp direct to scope or did he add the extra circuitry that you showed me ???

[kt315]

thinking he did use directly the output. i did search all his videos in his youtube channel, nothing tells about his skills in electronics.