Author Topic: Restoring a Rogowski coil calibrator  (Read 375 times)

Offline klugesmith

  • High Voltage Senior
  • *****
  • Posts: 741
  • Karma: +22/-0
    • View Profile
Restoring a Rogowski coil calibrator
« on: June 28, 2024, 07:56:46 AM »
This is to complete an unfinished thread from 4hv in 2010, about some DIY Rogowski coils and the beginnings of a calibrator.
https://4hv.org/e107_plugins/forum/forum_viewtopic.php?id=82880

Among boxes of stuff, I found some coils and the main part of original calibrator.
Originally powered by a 9 volt battery, it generated 40 amp oscillatory pulses, with similar shape and timing as can crusher pulses.
It's a simple LCR circuit where:
 C = 51.9 uF (as measured), about the same as my 22 KV Aerovox capacitor.
 L is an actual can crusher coil, roughly 2 uH if I recall correctly.
 Switch is a MOSFET, FDD8586 (now obsolete) with Rds on the order of 5 mΩ.
The loop has no intentional extra R. Total R and L can both be computed from measured frequency and damping. Then, from initial capacitor voltage, we can figure the peak current and initial di/dt value.

The main unit has a cable with 3 wires: charging power, gate drive, and common.
Not found was old solderless breadboard with 9V battery connector, 1500 ohm charging resistor, and 555 timer circuit for gate drive.
For check-out,  I substituted an existing breadboard circuit with a manual SPDT switch and debouncer.  Its 74HC00 gate IC limits voltage to 6 V, so peak current is about 26 A.  Each toggle from low to high produces one LCR discharge pulse. 
This was tested with both kinds of Rogowski coil. 

Got a phone picture of scope screen; measurement and analysis are a job for another day.
Yellow is capacitor voltage.   Blue and white are voltages from two different Rogowski coils.

The scope and simulation both show a detail mentioned at end of old 4hv thread.
Rogowski coil (RC) output is proportional to di/dt, which matches the voltage on ideal inductor.
Its phase noticably leads the capacitor voltage, by an angle that's larger when damping resistance is greater.
That means that at the end of initial step, when Q1 is fully On, the coil signal is beyond "top dead center" and is already sloping down.  That makes it tricky to use first high point in measurement of damping and/or period.

Next round here will be to measure the amplitudes, frequency, and damping.  Then solve for model parameters: L, R, and Rogowski coil sensotivity factors.   IIRC, the latter are expected to be about 32 nH and 39 nH based on geometric formulas given in the old 4hv report.
« Last Edit: June 28, 2024, 10:58:32 AM by klugesmith »

Offline klugesmith

  • High Voltage Senior
  • *****
  • Posts: 741
  • Karma: +22/-0
    • View Profile
Re: Restoring a Rogowski coil calibrator
« Reply #1 on: June 29, 2024, 10:23:10 PM »
Here's the schematic/sim file from previous post.   I think it will open in LTSPICE if extension is changed from .txt back to .asc.  A report of success or failure would be welcome!  * rlc_disch2.txt

Without Rogowski coils, I got some discharge waveforms before & after putting a can in the coil.
Also got waveforms from scope into a spreadsheet (which is not required for measuring amplitudes and frequency).

For these pictures the scope trigger is on Q1 gate instead of vC, so we can see proper time relation between Vc curves.  The spreadsheet plot includes an intermediate can position, with a small increase in frequency and damping.

Here the 52 uF capacitor was initially at 6.2 V, for energy of 1 mJ.
With 52 uF high voltage capacitor and suitable switch, we could turn the knob up to 6.2 kV.
Discharge should have exactly the same shape and timing, except 1000 times more current and 1 million times more energy.
Not counting minor increase in R from metal heating during the pulse, and major change in can geometry (it would end up in two pieces).

It will be interesting to match the can-presence effect in simulation model.  Have any can-crushing or coin-shrinking or disk-launching hobbyists worked on that?  We can lower the hurdle by ignoring changes in conductor geometry during the pulse.
« Last Edit: June 29, 2024, 10:44:01 PM by klugesmith »

Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2859
  • Karma: +134/-2
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: Restoring a Rogowski coil calibrator
« Reply #2 on: June 29, 2024, 11:40:56 PM »
Quote
I think it will open in LTSPICE if extension is changed from .txt back to .asc.  A report of success or failure would be welcome!  * rlc_disch2.txt
Yes, opens in LTSpice.  To simulate, needs a path to ground from one side or the other of L1.  Spice doesn't allow completely floating sets of nodes.  With that tweak, simulates fine.

David Knierim

Offline klugesmith

  • High Voltage Senior
  • *****
  • Posts: 741
  • Karma: +22/-0
    • View Profile
Re: Restoring a Rogowski coil calibrator
« Reply #3 on: June 30, 2024, 03:03:04 AM »
Good point Dave. It's a mystery why it works in my version of ltspicevii. I had overlooked that rule when I disconnected L1 from GND before original post,  to make a point. When I'm at computer, will investigate using .op directive, and also try disconnecting L1 from the E element (which is just for plot scaling convenience) to see if that breaks it.
« Last Edit: June 30, 2024, 03:09:31 AM by klugesmith »

Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2859
  • Karma: +134/-2
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: Restoring a Rogowski coil calibrator
« Reply #4 on: June 30, 2024, 03:57:13 AM »
Quote
It's a mystery why it works in my version of ltspicevii.
LTSpice has an option to automatically add a small parallel conductance to inductors to speed up simulation.  Perhaps other SPICE variants have options to automatically add small conductance to ground on floating nodes.
David Knierim

Offline klugesmith

  • High Voltage Senior
  • *****
  • Posts: 741
  • Karma: +22/-0
    • View Profile
Re: Restoring a Rogowski coil calibrator
« Reply #5 on: July 01, 2024, 08:48:53 PM »
You nailed it, Dave.  In LTspiceXVII under .OPTIONS, I found gfloat with default value of 1e-12.   
Setting .OPTIONS gfloat 0
brought a fatal error message saying "This circuit has floating nodes".
Correctable by adding an explicit DC path, even 1e12 ohm resistor, between L1 and another node.

In other news, I got the alpha and omega of first spreadsheeted Vc waveform. https://en.wikipedia.org/wiki/RLC_circuit
Damped omega is 91600 (14.58 kHz) and alpha is 7400.   Q is 6.21, zeta is 0.081, undamped omega is 91900 (14.63 kHz).
Consistent with C = 51.9 uF, L = 2.28 uH, R = 33.7 mΩ.
A next step is to get the di/dt values and Rogowski coil M values analytically.
And maybe experiment with different Q1 gate voltages, to see change in damping as Rds changes.
« Last Edit: July 01, 2024, 09:04:42 PM by klugesmith »

Offline klugesmith

  • High Voltage Senior
  • *****
  • Posts: 741
  • Karma: +22/-0
    • View Profile
Re: Restoring a Rogowski coil calibrator
« Reply #6 on: July 11, 2024, 06:30:00 PM »
Before sending any PCB Rogowski coils to friends, I wanted to check the matching of 5 specimens that have been cut out from their original big heavy disks. They are from at least two different fab lots.   

Didn't get to Rogowski coil sensitivity (mutual inductance), where we expect very close matching.

DC resistance ranges from about 0.9 to 1.2 ohms.  Might be attributed to variation in etch widths, copper foil thickness, and plating thickness in vias (which represent around 40% of the path length).

I was surprised to see self-inductance range from about 2.7 to 2.9 uH, in initial quick-and-dirty test. Any ideas how that could vary so much?
Measurement used another artifact from same old box:  a breadboarded oscillator copied from "PIC  based LC meter" by AADE (the late Neil Heckt).  Who needs a PIC when a frequency counter and spreadsheet calculator are at hand?   In this case, fixed capacitor is labeled 0.1 uF and fixed series inductor is labeled 51 uH.


Coils aren't going to be mailed until next week.   I want time to properly enlarge the central holes from 4 mm to 25 mm, using same old hole saw which I found in a tool drawer.
« Last Edit: July 11, 2024, 06:36:09 PM by klugesmith »

Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2859
  • Karma: +134/-2
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: Restoring a Rogowski coil calibrator
« Reply #7 on: July 11, 2024, 07:38:26 PM »
Quote
Any ideas how that could vary so much?
First thought would be ECB thickness.  Trace width would have some effect too.
David Knierim

High Voltage Forum

Re: Restoring a Rogowski coil calibrator
« Reply #7 on: July 11, 2024, 07:38:26 PM »

 


* Recent Topics and Posts

post Re: Problem with SSTC
[Solid State Tesla Coils (SSTC)]
Nunu00
July 12, 2024, 10:17:36 PM
post Making a HV prove
[Electronic Circuits]
Alberto
July 12, 2024, 09:01:08 PM
post Re: Problem with SSTC
[Solid State Tesla Coils (SSTC)]
davekni
July 12, 2024, 01:33:37 AM
post Re: Problem with SSTC
[Solid State Tesla Coils (SSTC)]
Nunu00
July 12, 2024, 12:17:32 AM
post Re: Restoring a Rogowski coil calibrator
[Capacitor Banks]
davekni
July 11, 2024, 07:38:26 PM
post Re: Restoring a Rogowski coil calibrator
[Capacitor Banks]
klugesmith
July 11, 2024, 06:30:00 PM
post LOD No Double Resonant SSTC?
[Solid State Tesla Coils (SSTC)]
ColinHeath
July 11, 2024, 06:08:30 PM
post Re: FIRST DRSSTC SKM400GB128D OCD SETTING
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Admiral Aaron Ravensdale
July 11, 2024, 12:24:56 PM
post Re: Strange QCW Streamer Behavior
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
July 11, 2024, 06:42:23 AM
post Re: Syntherrupter Lightsaber Sender Programming
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
Cameron Prince
July 11, 2024, 05:46:07 AM
post Syntherrupter Lightsaber Sender Programming
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
Cameron Prince
July 11, 2024, 05:26:51 AM
post Re: Strange QCW Streamer Behavior
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ZakW
July 11, 2024, 02:50:54 AM
post Strange QCW Streamer Behavior
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Coupling
July 11, 2024, 12:59:55 AM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic Circuits]
petespaco
July 10, 2024, 07:10:34 PM
post Re: Understanding and tracking upper and lower poles of QCW DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
July 10, 2024, 06:52:42 PM
post Re: Understanding and tracking upper and lower poles of QCW DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Anders Mikkelsen
July 10, 2024, 06:28:19 PM
post Re: FIRST DRSSTC SKM400GB128D OCD SETTING
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Alex_1996
July 10, 2024, 01:34:09 PM
post Re: Silicon(e) plasma
[General Chat]
alan sailer
July 10, 2024, 12:09:06 AM
post Re: Problem with SSTC
[Solid State Tesla Coils (SSTC)]
Nunu00
July 09, 2024, 11:52:00 PM
post Understanding and tracking upper and lower poles of QCW DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Simranjit
July 09, 2024, 07:37:22 PM
post Re: Silicon(e) plasma
[General Chat]
MechatEng2023
July 09, 2024, 07:30:05 PM
post Re: UD2.7C outputs very odd single square wave pulses
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
July 09, 2024, 03:30:49 AM
post Re: UD2.7C outputs very odd single square wave pulses
[Dual Resonant Solid State Tesla coils (DRSSTC)]
verliebt_in_neukölln17
July 09, 2024, 12:51:02 AM
post Re: UD2.7C outputs very odd single square wave pulses
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
July 08, 2024, 11:30:44 PM
post Re: Why so cheap?
[General Chat]
alan sailer
July 08, 2024, 10:57:10 PM
post UD2.7C outputs very odd single square wave pulses
[Dual Resonant Solid State Tesla coils (DRSSTC)]
verliebt_in_neukölln17
July 08, 2024, 10:21:01 PM
post Why so cheap?
[General Chat]
MRMILSTAR
July 08, 2024, 09:55:24 PM
post Re: Syntherrupter - A Feature-rich, Polyphonic Interrupter
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
Cameron Prince
July 08, 2024, 09:18:21 PM
post Re: Syntherrupter - A Feature-rich, Polyphonic Interrupter
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
Max
July 08, 2024, 05:17:49 PM
post Re: Syntherrupter - A Feature-rich, Polyphonic Interrupter
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
Cameron Prince
July 08, 2024, 04:49:20 PM
post Re: Tesla coil in FEMM
[Beginners]
Simranjit
July 08, 2024, 04:28:43 AM
post Re: Tesla coil in FEMM
[Beginners]
davekni
July 08, 2024, 04:06:53 AM
post Tesla coil in FEMM
[Beginners]
Simranjit
July 08, 2024, 03:46:49 AM
post Re: Best core material for QCW Buck modulator ?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Simranjit
July 08, 2024, 02:42:00 AM
post Re: QCWDRSSTC - Project Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ZakW
July 08, 2024, 01:37:55 AM
post Re: First DRSSTC Build- Issues with Fibernet project
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Sebigamer
July 08, 2024, 12:53:08 AM
post Re: QCWDRSSTC - Project Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Anders Mikkelsen
July 08, 2024, 12:49:48 AM
post Re: Silicon(e) plasma
[General Chat]
alan sailer
July 07, 2024, 11:15:35 PM
post Silicon(e) plasma
[General Chat]
MechatEng2023
July 07, 2024, 11:04:43 PM
post Re: QCWDRSSTC - Project Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ZakW
July 07, 2024, 09:39:07 PM
post Re: First DRSSTC Build- Issues with Fibernet project
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
July 07, 2024, 05:32:56 PM
post Re: QCWDRSSTC - Project Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Anders Mikkelsen
July 07, 2024, 02:52:19 PM
post Re: No change in Phase Lead
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Anders Mikkelsen
July 07, 2024, 02:50:04 PM
post Re: Best core material for QCW Buck modulator ?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Anders Mikkelsen
July 07, 2024, 02:20:11 PM
post Teardown of a APC SmartUPS VT 40 kVA
[Electronic Circuits]
Mads Barnkob
July 07, 2024, 10:02:22 AM
post First DRSSTC Build- Issues with Fibernet project
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Sebigamer
July 07, 2024, 09:23:58 AM
post Re: QCWDRSSTC - Project Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ZakW
July 07, 2024, 12:44:53 AM
post Re: FEMM tesla coil simulation
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Simranjit
July 07, 2024, 12:08:50 AM
post Re: FEMM tesla coil simulation
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
July 06, 2024, 10:35:49 PM
post FEMM tesla coil simulation
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Simranjit
July 06, 2024, 09:42:43 PM
post Re: No change in Phase Lead
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
July 06, 2024, 06:06:23 PM
post Re: No change in Phase Lead
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Admiral Aaron Ravensdale
July 06, 2024, 10:21:16 AM
post Re: No change in Phase Lead
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Admiral Aaron Ravensdale
July 06, 2024, 10:15:42 AM
post Re: QCWDRSSTC - Project Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Simranjit
July 06, 2024, 04:53:56 AM
post Re: No change in Phase Lead
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
July 06, 2024, 04:42:16 AM
post Re: QCWDRSSTC - Project Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
July 06, 2024, 04:09:50 AM
post Re: Best core material for QCW Buck modulator ?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
July 06, 2024, 03:07:11 AM
post Re: No change in Phase Lead
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
July 06, 2024, 03:05:18 AM
post Re: QCWDRSSTC - Project Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ZakW
July 06, 2024, 02:37:16 AM
post Re: QCWDRSSTC - Project Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Simranjit
July 06, 2024, 02:20:14 AM
post QCWDRSSTC - Project Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ZakW
July 06, 2024, 01:55:14 AM
post Re: No change in Phase Lead
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
July 05, 2024, 11:50:37 PM
post Best core material for QCW Buck modulator ?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Simranjit
July 05, 2024, 10:07:04 PM
post 230v Tesla coil and krypton gas
[Spark Gap Tesla Coils (SGTC)]
gravitysrainbow
July 05, 2024, 07:13:25 PM
post Re: No change in Phase Lead
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Admiral Aaron Ravensdale
July 05, 2024, 06:17:13 PM
post Re: Phase lead inductors
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
July 04, 2024, 11:40:45 PM
post Re: Sling Psychrometer
[Laboratories, Equipment and Tools]
Twospoons
July 04, 2024, 11:02:32 PM
post Phase lead inductors
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
July 04, 2024, 06:28:08 PM
post Re: Sling Psychrometer
[Laboratories, Equipment and Tools]
klugesmith
July 04, 2024, 12:31:40 AM
post Re: FIRST DRSSTC SKM400GB128D OCD SETTING
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Alex_1996
July 04, 2024, 12:07:21 AM
post Re: FIRST DRSSTC SKM400GB128D OCD SETTING
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Alex_1996
July 04, 2024, 12:06:17 AM
post Re: FIRST DRSSTC SKM400GB128D OCD SETTING
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
July 03, 2024, 10:51:23 PM
post Re: FIRST DRSSTC SKM400GB128D OCD SETTING
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
July 03, 2024, 09:44:14 PM
post Re: Coax cable for DRSSTC interrupter?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Admiral Aaron Ravensdale
July 03, 2024, 08:48:13 PM
post Re: Coax cable for DRSSTC interrupter?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Simranjit
July 03, 2024, 08:24:50 PM
post Re: FIRST DRSSTC SKM400GB128D OCD SETTING
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Alex_1996
July 03, 2024, 08:12:55 PM
post Re: Coax cable for DRSSTC interrupter?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Admiral Aaron Ravensdale
July 03, 2024, 07:29:53 PM
post Re: FIRST DRSSTC SKM400GB128D OCD SETTING
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Admiral Aaron Ravensdale
July 03, 2024, 07:21:38 PM
post Re: FIRST DRSSTC SKM400GB128D OCD SETTING
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
July 03, 2024, 05:05:39 PM
post Re: FIRST DRSSTC SKM400GB128D OCD SETTING
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Alex_1996
July 03, 2024, 04:29:53 PM
post Re: FIRST DRSSTC SKM400GB128D OCD SETTING
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
July 03, 2024, 04:09:11 PM
post FIRST DRSSTC SKM400GB128D OCD SETTING
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Alex_1996
July 03, 2024, 02:47:18 PM
post Re: Eliminating discharges from a SSTC
[Solid State Tesla Coils (SSTC)]
Alex_1996
July 03, 2024, 01:35:24 PM
post Re: Coax cable for DRSSTC interrupter?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
July 03, 2024, 02:19:03 AM
post Re: Coax cable for DRSSTC interrupter?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
verliebt_in_neukölln17
July 03, 2024, 01:19:50 AM
post Coax cable for DRSSTC interrupter?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Simranjit
July 02, 2024, 11:29:18 PM
post Re: Is this a good pulse experiment capacitor?
[Capacitor Banks]
Mads Barnkob
July 02, 2024, 09:59:07 PM
post Re: LabCoatz Staccato QCW No straight sparks
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ZakW
July 02, 2024, 09:55:53 PM
post Re: Capacitor wiring for single phase 240 to split phase (180 degree) 240v
[Capacitor Banks]
klugesmith
July 02, 2024, 09:44:55 PM
post Re: LabCoatz Staccato QCW No straight sparks
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Admiral Aaron Ravensdale
July 02, 2024, 07:51:37 PM
post Re: LabCoatz Staccato QCW No straight sparks
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ZakW
July 02, 2024, 06:14:07 PM
post Is this a good pulse experiment capacitor?
[Capacitor Banks]
FPS
July 02, 2024, 06:02:38 PM
post Re: LabCoatz Staccato QCW No straight sparks
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Admiral Aaron Ravensdale
July 02, 2024, 11:37:46 AM
post Re: Building my first DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
July 02, 2024, 05:22:10 AM
post Re: Coulometric hourmeters
[Laboratories, Equipment and Tools]
davekni
July 02, 2024, 05:16:30 AM
post Re: Building my first DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
drobotk
July 01, 2024, 11:50:12 PM
post Re: Restoring a Rogowski coil calibrator
[Capacitor Banks]
klugesmith
July 01, 2024, 08:48:53 PM
post Uses for Weston's Little Bee probe
[Laboratories, Equipment and Tools]
klugesmith
July 01, 2024, 08:40:59 AM
post Re: Coulometric hourmeters
[Laboratories, Equipment and Tools]
klugesmith
July 01, 2024, 08:09:42 AM
post Re: Coulometric hourmeters
[Laboratories, Equipment and Tools]
davekni
June 30, 2024, 06:49:45 AM

Sitemap 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 
SimplePortal 2.3.6 © 2008-2014, SimplePortal