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THE AM BULLETIN BOARD => Technical Forum => Topic started by: w9jsw on January 13, 2023, 08:02:08 AM



Title: LC Meter/Bridge
Post by: w9jsw on January 13, 2023, 08:02:08 AM
What are you folks using for an _accurate_ LC meter. I am working on tank coil values and suspect that my inexpensive hobby LC100 unit is not accurate at low inductance values. What is a good choice for accurate uH measuring that is reasonable cost?

John


Title: Re: LC Meter/Bridge
Post by: KA3EKH on January 13, 2023, 09:02:32 AM
I have a huge General Radio 650 Impedance bridge that I picked up for $20, it got to be at least fifty or sixty years old if not older but with the internal 1 Kc oscillator and just a pair of headphones you can get real good readings on the impedance of chokes and transformers. Donít know what the highest usable frequency would be using external excitation and an external detector but can see it working up to 10 or 12 Mc without issue. Also allows you to do real accurate DC resistances, like out to a decimal point on low value resistances.
Think the trick is to start out and learn how to use it working with items of know quantity and then you can progress to unknown values. The huge size and Walnut case along with the overall look of something from the nineteen thirties were a plus for me, but in this world of everyone wanting micro size Chinese junk can see where that may not appeal to everyone.


Title: Re: LC Meter/Bridge
Post by: W1ITT on January 13, 2023, 09:49:12 AM
John..  Keep on the lookout for an AADE LC meter.  Almost All Digital Equipment was a one-man shop and is out of business now.  Neil is SK.  His LC meter is handy, palm sized and self contained.  You can zero out fixtures on both the L and C ranges so as to measure just the component and not the strays.  I have taken mine all over the world to do the initial setup on phased arrays and it saves time and stress.    I think they cost about $100 a decade or so ago. 
73 de Norm W1ITT


Title: Re: LC Meter/Bridge
Post by: KD1SH on January 13, 2023, 10:03:48 AM
This has been my go-to for a few years now: https://www.deree.com.tw/de-5000-lcr-meter.html
I have no calibrated laboratory gear to compare it to, but it seems accurate and provides a lot of information.


Title: Re: LC Meter/Bridge
Post by: w9jsw on January 13, 2023, 10:19:49 AM
Wondering if I should be looking for an Autek RF-1 so I can check the tank L at frequency, as well as do all sorts of antenna experiments?

The DE-5000 also has my eye. How accurate does it seem to be when extrapolating the inductance at measurement vs. a coil at 1.9MHz for instance?

Does the Q feature bring more to the party? I have been using SimSmith lately and being able to measure inductance and Q would be quite useful.

John


Title: Re: LC Meter/Bridge
Post by: KD1SH on January 13, 2023, 10:46:55 AM
I've used it to read the inductance and Q of brand-new 1% tolerance small value inductors, and it seems very accurate. I've also compared its readings to my own extrapolated predictions arrived at by various methods including sweeping with my RF generator and using a grid dip meter, and it all seems right on. I'm sure it's not the equivalent of a kilo-buck lab instrument, but my use it's fantastic.

Wondering if I should be looking for an Autek RF-1 so I can check the tank L at frequency, as well as do all sorts of antenna experiments?

The DE-5000 also has my eye. How accurate does it seem to be when extrapolating the inductance at measurement vs. a coil at 1.9MHz for instance?

Does the Q feature bring more to the party? I have been using SimSmith lately and being able to measure inductance and Q would be quite useful.

John


Title: Re: LC Meter/Bridge
Post by: Carl WA1KPD on January 13, 2023, 03:03:26 PM
John..  Keep on the lookout for an AADE LC meter.  Almost All Digital Equipment was a one-man shop and is out of business now.  Neil is SK.  His LC meter is handy, palm sized and self contained.  You can zero out fixtures on both the L and C ranges so as to measure just the component and not the strays.  I have taken mine all over the world to do the initial setup on phased arrays and it saves time and stress.    I think they cost about $100 a decade or so ago. 
73 de Norm W1ITT


I love mine and am sorry they are no longer available.
But in doing some BC work I discovered it will not measure coils that large.

Not a deal killer, to me,  just something to be aware.


Title: Re: LC Meter/Bridge
Post by: km6sn on January 13, 2023, 08:56:26 PM
Best LC meter I ever had is homebrew, measuring to 1%, from this article
https://www.qsl.net/wm5z/cq199301b.pdf

I wrote arduino code to do the calcs and display, and calibration.\
email me at  km6sn@fastmail.com for the code.

The configuration is simple:  a 74AC74 doing a divide-by-4 prescaler,
a 16 MHz arduino, and the human interface is via the serial port on the arduino.

The 74AC74 was mounted dead-bug, with a s/m 100n bypass right at the power pin.
 Be aware that the 74AC74 clock input  will trigger on analog signals, so no A/D is required. I probably biased the input clock line to vcc/2 .

The whole thing, arduino and  all, mounted on perfboard with a ground plane.

I used an Arduino Uno R3, which has a USB-B (large) connector for the serial port. I mounted the Arduino  so the USB connector stuck out  from a hole in
the chassis for ease of serial connection.

Then a USB serial board (FTDI) at the laptop end.


GL,

Rod


Title: Re: LC Meter/Bridge
Post by: WA4WAX on January 14, 2023, 09:33:53 AM
I have a DE-6000 and love it.  It is out of production and a bit hard to find.  DE-5000 is fairly easy to find, and just as good for most applications.

I have an All Digital L/C meter and will sell it. It is like new.


Title: Re: LC Meter/Bridge
Post by: K9MB on January 14, 2023, 10:36:35 AM
What are you folks using for an _accurate_ LC meter. I am working on tank coil values and suspect that my inexpensive hobby LC100 unit is not accurate at low inductance values. What is a good choice for accurate uH measuring that is reasonable cost?

John

John,
I have several meters and my favorite is the Tenma 73-960
Excellent range and good accuracy.

https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313&_nkw=tenma+72-960&_sacat=0



https://datasheet.octopart.com/72-960-Tenma-datasheet-20064.pdf

Here are several for sale on Ebay used.

I also like my M4070 for smaller inductors
The 4070 and the Tenma give very close results in uH ranges.
Tenma better to measure big reactors and chokes and mod tranny windings.

https://www.amazon.com/s?k=M4070+lcr+meter&crid=3D3QH8SVL094R&sprefix=m4070+lcr+meter%2Caps%2C110&ref=nb_sb_noss

73, Mike


Title: Re: LC Meter/Bridge
Post by: WU2D on January 21, 2023, 09:34:37 PM
I use the Boonton 160A. It gives Q and measures L and C and works great right where we need it in the HF band.

I also have a Boonton 250 RX Meter that would work as well, but the 160 is so fast and its the balls for seeing what happens to Q at specific frequencies.


Title: Re: LC Meter/Bridge
Post by: w9jsw on January 22, 2023, 07:02:21 AM
Is anyone familiar with the B&K offerings? 2 of them offer ESR capabilities.

https://www.mouser.com/datasheet/2/43/87xB_datasheet-2487040.pdf

John


Title: Re: LC Meter/Bridge
Post by: w9jsw on January 22, 2023, 09:35:52 AM
I use the Boonton 160A. It gives Q and measures L and C and works great right where we need it in the HF band.

I also have a Boonton 250 RX Meter that would work as well, but the 160 is so fast and its the balls for seeing what happens to Q at specific frequencies.

A good video of the unit. This is something I will look for at the hamfests.

https://www.youtube.com/watch?v=L2005LTmE7Q


Title: Re: LC Meter/Bridge
Post by: WD5JKO on January 22, 2023, 12:41:56 PM
Wondering if I should be looking for an Autek RF-1 so I can check the tank L at frequency, as well as do all sorts of antenna experiments?

Hi John,

  I have an RF-1, and for me it is a keeper. Sure, it is old now, low end, and suffered from build quality issues. Mine needed many connections within resoldered, or soldered for the first time!
I saw one on Ebay yesterday for $80.

   Whatever you use, the connection to the device under test is where a lot of the the inaccuracies come from. Some have a calibration kit, to take out lead-length with an "open", "short", and "50 Ohm" standard. With something like an RF-1, that option does not exist, so you must measure at the connector (SO-239) with minimal lead length. The RF-1 does measure at the frequency of interest between 160-10m, a big advantage. It is quite useful measuring low value capacitors, like 47pf, or to measure the series resonance of a 0.01uf cap versus lead length (usually around 7-9 Mhz). I recently wound some toroids using mine, and the measurements closely matched the coil calculations.

   As the frequency of interest goes up, those LCR boxes using a fixed low frequency test signal become pretty darn inaccurate.

Good luck with your search!

Jim
Wd5JKO





Title: Re: LC Meter/Bridge
Post by: DMOD on January 25, 2023, 07:01:27 PM
Is anyone familiar with the B&K offerings? 2 of them offer ESR capabilities.

https://www.mouser.com/datasheet/2/43/87xB_datasheet-2487040.pdf

John

I have an older B&K, have had it for 11 years, it is very accurate, and has never failed.

Phil


Title: Re: LC Meter/Bridge
Post by: MikeKE0ZUinkcmo on January 26, 2023, 03:15:37 AM
If you're interested in the Boonton, I would also suggest you look for the 260 as well.   A bit more modern and easier to use.  

(https://photos.smugmug.com/TEST-EQUIPMENT/BOONTON/Q-Meter-Model-260/i-3q4dqbG/0/f191f460/L/103%20Test-L.jpg) (https://mikeharrison.smugmug.com/TEST-EQUIPMENT/BOONTON/Q-Meter-Model-260/i-4JnB9c9/A)  

Another Boonton meter thats handy for RF, is the 250 Rx meter.

(https://photos.smugmug.com/TEST-EQUIPMENT/BOONTON/Rx-meter-Model-250/i-MJfWXW6/0/5b7797a7/XL/PA1-XL.jpg) (https://mikeharrison.smugmug.com/TEST-EQUIPMENT/BOONTON/Rx-meter-Model-250/i-hLNPmb2/A)

Be sure to take a small coil of roughly known inductance, and the value of capacitance needed to resonate at your chosen test frequency, with you to test what ever bridge you may find.   The Boonton's often have blown thermocouples because of misadjustment during the testing process by those that won't or can't read manuals, making them useless.  To that end, I'd recommend a quick read of the manual beforehand to familiarize yourself with the meter.

These old guys are slow to use, but accurate.
AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands