LM318 and uA709

[sharky]

I am using a 2 coil Pi, one for TX and one for RX both electrically isolated with optocoupler, I have to imagine the rx coil doesnt reduce the signal level from the target, can anyone measure this with a nce sensitive scope. Is there a better IC other than LM318 with slew rate of 50, and noise figure of < 4nV, can we replace the schematic directly by LM318 removing the uA709 in the project
Twin Loop Treasure Seeker (Robert & David Crone, ETI LINK http://geotech.thunting.com/cgi-bin/...loop/index.dat), Just look at the compensation and the pin8 connection, can we eplace the schematics uA709 withLM318. whats the noise figure for LM318...

regards

[Max]

I am using a 2 coil Pi, one for TX and one for RX both electrically isolated with optocoupler, I have to imagine the rx coil doesnt reduce the signal level from the target, can anyone measure this with a nce sensitive scope. Is there a better IC other than LM318 with slew rate of 50, and noise figure of < 4nV, can we replace the schematic directly by LM318 removing the uA709 in the project
Twin Loop Treasure Seeker (Robert & David Crone, ETI LINK http://geotech.thunting.com/cgi-bin/...loop/index.dat), Just look at the compensation and the pin8 connection, can we eplace the schematics uA709 withLM318. whats the noise figure for LM318...

regards

Hi sharky,
that one was a very old project and also a bad one... bad sens.
Anyway, 50V/us is a big slew-rate but often you don't need as higher.
Best preamp. I've found suitable and used in PI are:

NE5534 (SR = 13 V/us typ)
LF356 (SR = 12 V/us typ)

Many good PI have one or the other...
Both are low noise. Of course you can use some OP37 etc but then don't expect miracles.

If you need a good PI for depth I suggest you make the DeltaPulse.

Kind regards,
Max

PS
noise for LM318 is 15 nV/√Hz
noise for NE5534 is 3.5 nV/√Hz
noise for LF356 is 12 nV/√Hz

[sharky]

Hi MAX

Are u sure 10V/us slew is sufficient !!!!

Can I replace a mono IC opamp(not dual opamp) or op37 directly into the IC socket of below project,lookat pin 5,8 of uA709.

What I find in National datasheet is these are not recommended for sonar and radar, they recommend a Slew of 300V/us and noise of 5nV and our PI is variable from 100hz to 1.5Khz

I have redesigned the Circuit of twinloop(Twin Loop Treasure Seeker Robert & David Crone) and am using the same pcb(as i have no time for new pcb design, exhausted by now) as these are leftout with me apart from Stuarts PI PCB's.

I removed one coil, changed the resistors at Ne555's timing, PW,PD, frequency resistors and inserted in series Pots to get variable PW,Freq,PD. changed the TIP transistor to IRF740, lets see how this works till I get a Guru, even if a better detector is there we need a Guru as these places are haunted,protected.

Can we replace the uA709 directly with those bal/comp around, and taking the +ve input to somewhere may be across the coil

[Max]

Hi MAX

Are u sure 10V/us slew is sufficient !!!!

Can I replace a mono IC opamp(not dual opamp) or op37 directly into the IC socket of below project,lookat pin 5,8 of uA709.

What I find in National datasheet is these are not recommended for sonar and radar, they recommend a Slew of 300V/us and noise of 5nV and our PI is variable from 100hz to 1.5Khz

I have redesigned the Circuit of twinloop(Twin Loop Treasure Seeker Robert & David Crone) and am using the same pcb(as i have no time for new pcb design, exhausted by now) as these are leftout with me apart from Stuarts PI PCB's.

I removed one coil, changed the resistors at Ne555's timing, PW,PD, frequency resistors and inserted in series Pots to get variable PW,Freq,PD. changed the TIP transistor to IRF740, lets see how this works till I get a Guru, even if a better detector is there we need a Guru as these places are haunted,protected.

Can we replace the uA709 directly with those bal/comp around, and taking the +ve input to somewhere may be across the coil

Hi,
PI is not GPR. You can't detect e.g. hollows with it. Just conductive items, metals.

About the comp/bal pins if you watch at datasheets of op. amps. you'll see on some pins the label NC that means "not connected" internally.
If that's the case you can leave there the comp/bal circuitry cause no alteration occours by that components.
In some cases you need to change the e.g. bal. trimmer and connection with some pins as explained in the datasheet, to gain zero voltage (about) at output when inputs are held at zero volt.
That's the offset adjustement. Often not required in PI, with that newer components cause devices offsets are so small that don't require you'll adjust them.

Best regards,
Max

[Carlos]

look this post, I change the uA709 for the Lm318 and put the mosfet IRF740, I modificated the PCB of the Gerber PI

Carlos


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