Tetra Replication

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Itsu

Re: Tetra Replication « Reply #175 on: 2025-02-28, 10:04:57 »

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Quote from: verpies on 2025-02-27, 22:01:29

Yes, you need a HV probe to acquire the voltage signal but why do you need a HV probe across the CSR ?

Well, i measure 600Vpp there using my P5100 HV probe, so i am hesitating to connect a normal probe acoss the csr.

But i can try using the alternative probe connections for the csr you suggested.

Itsu

verpies

Re: Tetra Replication « Reply #176 on: 2025-02-28, 14:42:05 »

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Quote from: Itsu on 2025-02-28, 10:04:57

Well, i measure 600Vpp there using my P5100 HV probe...

600V across a 1Ω CSR would mean 600A !!!. Are you sure about that?
Do you have 0.1Ω CSR ?

verpies	Re: Tetra Replication « Reply #177 on: 2025-02-28, 14:55:22 »
Group: Professor Hero Member Posts: 3670	Quote from: bte on 2025-02-28, 02:25:27 Raspberry pi has gpio exposed to userspace also. Can the GPIO be bitbanged from user mode without interruption or will the Task Scheduler preempt it ?

bte

Re: Tetra Replication « Reply #178 on: 2025-02-28, 15:50:03 »

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Quote from: verpies on 2025-02-28, 14:55:22

Can the GPIO be bitbanged from user mode without interruption or will the Task Scheduler preempt it ?

It's like a read() or write(), not fast relatively speaking.

Itsu	Re: Tetra Replication « Reply #179 on: 2025-02-28, 15:57:42 »
Group: Elite Experimentalist Hero Member Posts: 4236	Quote from: verpies on 2025-02-28, 14:42:05 600V across a 1Ω CSR would mean 600A !!!. Are you sure about that? Do you have 0.1Ω CSR ? Yes, i am sure, at least that's what the scope shows, but i think it might be bogus readout as i just used a 0.1 Ohm csr and it measures still 500Vpp across it I think the pulse is messing up this current reading. I used the P5100 HV probe. ------------------------ Tetra Replication 0.1 Ohm csr.png (21.97 kB, 640x600 - viewed 216 times.)

verpies	Re: Tetra Replication « Reply #180 on: 2025-02-28, 20:21:58 »
Group: Professor Hero Member Posts: 3670	Quote from: Itsu on 2025-02-28, 15:57:42 I think the pulse is messing up this current reading. I used the P5100 HV probe. HV probes can be susceptible to EMI ingress post the internal voltage divider. IMO if you use a regular probe across the 0.1Ω CSR your scope will be safe and you will get a different reading. You can try it with the Owon first if you have trepidations.

Itsu	Re: Tetra Replication « Reply #181 on: 2025-02-28, 21:25:23 »
Group: Elite Experimentalist Hero Member Posts: 4236	I used my normal probe (P6139B) on the 0.1 Ohm csr, but still the recorded voltage is way too high, 234.8V IMO (2348A??). See screenshot ------------------------ Tetra Replication 0.1 Ohm csr normal probe P6139B.png (20.11 kB, 640x600 - viewed 191 times.)

verpies	Re: Tetra Replication « Reply #182 on: 2025-02-28, 22:24:25 »
Group: Professor Hero Member Posts: 3670	Is it a high-quality CSR ? ...any inductance ?

verpies	Re: Tetra Replication « Reply #183 on: 2025-02-28, 22:53:53 »
Group: Professor Hero Member Posts: 3670	Quote from: Itsu on 2025-02-27, 15:36:42 The rise time always was longer as the fall time, but it gets worse when using more induction / capacitance in the DUT (50 Ohm induction free resistor is the best). It's important to remember that this nanopulser is a current source. A proverbial battery and a switch is a voltage source. Their response to loads are different by definition.

Itsu	Re: Tetra Replication « Reply #184 on: 2025-03-01, 09:27:33 »
Group: Elite Experimentalist Hero Member Posts: 4236	Quote from: verpies on 2025-02-28, 22:24:25 Is it a high-quality CSR ? ...any inductance ? Its a Ohmite 13FR100E which states: "100 mOhms ±1% 3W Through Hole Resistor Axial Current Sense, Non-Inductive Metal Element" I have some other brands / types which i can try too.

verpies	Re: Tetra Replication « Reply #185 on: 2025-03-01, 11:25:22 »
Group: Professor Hero Member Posts: 3670	Quote from: Itsu on 2025-03-01, 09:27:33 I have some other brands / types which i can try too. What happens if you use a 0Ω CSR, i.e. shorted probe ?

Itsu	Re: Tetra Replication « Reply #186 on: 2025-03-01, 13:43:38 »
Group: Elite Experimentalist Hero Member Posts: 4236	Using the normal probe ground lead (0.5cm between tip and ground) i get similar result as with the 0.1 Ohm csr, something like 230Vpp. Using a probe with ground spring (RF tip) like shown below (also about 0.5cm between tips) i get 41Vpp, see screenshot. Itsu ------------------------ Tetra Replication rf tip.png (73.49 kB, 323x322 - viewed 161 times.) Tetra Replication shorted probe with RF tips.png (18.81 kB, 640x600 - viewed 147 times.)

bte	Re: Tetra Replication « Reply #187 on: 2025-03-01, 15:36:40 »
Group: Moderator Sr. Member Posts: 308	Quote from: Itsu on 2025-02-27, 19:54:26 Well, the problem is more the fact that i need 2 HV probes, and i only have one which is reliable (tektronix). But i used 2, the Tek (x100) one for voltage (yellow) and the other one (x1000) for current (green). I have the 1 Ohm csr (again / still) on the low side (anode of the diode) with both probes ground leads on the anode. The current probe is then across the 1 Ohm csr and voltage probe across both 1 Ohm csr and spool of wire (so measuring the extra 1 Ohm). Diagram attached. I tuned the pulse driving the pulser to max, but there was not much gain. Screenshot below, green current, yellow Voltage: It seems the "10 units of time" that Spherics referred to may be "10 nanoseconds" or so. Seems to be a delay of 10ns from voltage ramp up to current flow. Interesting. From everything I've read and from simulation there should be no time delay at all. Very interesting.

bte	Re: Tetra Replication « Reply #188 on: 2025-03-01, 15:39:05 »
Group: Moderator Sr. Member Posts: 308	Quote from: Itsu on 2025-02-28, 21:25:23 I used my normal probe (P6139B) on the 0.1 Ohm csr, but still the recorded voltage is way too high, 234.8V IMO (2348A??). See screenshot It's strange that the voltage is so high, it's like it's picking up the pulse and not really measuring the current? Correct me if I'm wrong? Some sort of inductive coupling? I don't know what to make of the large voltage across such a small resistance like that. I would have predicted voltages in the millivolt range from a 0.1 ohm sense resistor.

bte	Re: Tetra Replication « Reply #189 on: 2025-03-01, 15:41:14 »
Group: Moderator Sr. Member Posts: 308	Does the voltage persist when the coil is kept far away from the probe (long leads)?

verpies	Re: Tetra Replication « Reply #190 on: 2025-03-01, 17:16:17 »
Group: Professor Hero Member Posts: 3670	Quote from: bte on 2025-03-01, 15:39:05 It's strange that the voltage is so high, it's like it's picking up the pulse and not really measuring the current? Correct me if I'm wrong? Some sort of inductive coupling? Induction in the ground lead - certainly ...with a touch of common mode error. I am more concerned with the latter. Anyway, an amplitude error should not cause a timing error. Quote from: bte on 2025-03-01, 15:39:05 I don't know what to make of the large voltage across such a small resistance like that. I would have predicted voltages in the millivolt range from a 0.1 ohm sense resistor. For small currents maybe. For e.g. 10A, the voltage drop across a 0.1Ω resistor is 1V.

Itsu	Re: Tetra Replication « Reply #191 on: 2025-03-01, 21:21:37 »
Group: Elite Experimentalist Hero Member Posts: 4236	Quote from: bte on 2025-03-01, 15:41:14 Does the voltage persist when the coil is kept far away from the probe (long leads)? I don't think so as the longer (csr) leads would introduce more inductance in the circuit, but i did not try. Itsu

bte	Re: Tetra Replication « Reply #192 on: 2025-03-04, 23:03:16 »
Group: Moderator Sr. Member Posts: 308	I want to try to visualize the fields current induction effects. Thinking of making an array of single loop probes to map out the field intensity at each point. Spherics said the field should corkscrew around the toroid as the spherical waves intersect. With no external magnetic field the frequency needed is in the mhz range, but with a strong magnetic field, he stated the pulse repetition rate can be as low as 3khz. I'd like the understand this more. My hypothesis is, if the effect is real, then the waves are probably still propagating near the speed of light, but the magnetic field is causing the "reset" or "relaxation" period to be much much longer. This allows the time separated pulses to cause field rotation. I'd like to explore this thoroughly if I get positive results (current induction in my output coil). My theory is if you wind the output coil such that the windings are exactly in line with the corkscrewing action of the field, you should get enormous voltages and currents.

verpies	Re: Tetra Replication « Reply #193 on: 2025-03-04, 23:12:56 »
Group: Professor Hero Member Posts: 3670	Quote from: bte on 2025-03-04, 23:03:16 Thinking of making an array of single loop probes to map out the field intensity at each point. Here is a video about making an H-probe for your oscilloscope (it only picks up pulsating or alternating magnetic fields). This probe will not pick up constant magnetic fields. For those use a Hall sensor like the one Itsu has. Quote from: bte on 2025-03-04, 23:03:16 With no external magnetic field the frequency needed is in the MHz range, but with a strong magnetic field, he stated the pulse repetition rate can be as low as 3khz. I'd like the understand this more. If this decrease of frequency involves metallic iron, then I understand it. If it involves copper only - then I do not understand it. « Last Edit: 2025-03-05, 01:24:17 by verpies »

bte	Re: Tetra Replication « Reply #194 on: 2025-03-04, 23:24:52 »
Group: Moderator Sr. Member Posts: 308	It must relate to how iron behaves in some way.

verpies	Re: Tetra Replication « Reply #195 on: 2025-03-05, 01:23:04 »
Group: Professor Hero Member Posts: 3670	Quote from: bte on 2025-03-04, 23:24:52 It must relate to how iron behaves in some way. Is there Iron anywhere in the Tetra device ?

bte	Re: Tetra Replication « Reply #196 on: 2025-03-05, 01:26:49 »
Group: Moderator Sr. Member Posts: 308	No, all air core coils. Spherics stated not to use iron anywhere as it will only cause heat buildup and nullify the effect completely (odd). I've ordered a high voltage power supply today. Should be here end of March. Experimenting is so expensive. Timing board should be done this weekend.

verpies	Re: Tetra Replication « Reply #197 on: 2025-03-05, 01:31:58 »
Group: Professor Hero Member Posts: 3670	Quote from: bte on 2025-03-05, 01:26:49 No, all air core coils. "Air core coils" can still be wound with iron wire Quote from: bte on 2025-03-05, 01:26:49 I've ordered a high voltage power supply today. What voltage and amperage ?

bte	Re: Tetra Replication « Reply #198 on: 2025-03-05, 01:56:23 »
Group: Moderator Sr. Member Posts: 308	300V, 3A

bte	Re: Tetra Replication « Reply #199 on: 2025-03-08, 14:57:18 »
Group: Moderator Sr. Member Posts: 308	Wow the power supply arrived today! Great! The driver boards also shipped. Need to get timing board sent out for fabrication and order some solder paste/flux.