If you own a 30 MHz 4285A LCR meter, you may have discovered that you should perform a cable compensation if using 1 m or 2 m cables. You need

* Supplied 100 ohm resistor?

* 42090A open

* 42091A short?

The latter are over $1200 each. The 4285A LCR manual tells you how cobble together the open and short using BNC adapters if you don’t have the 42090A and 42091A, but I decided to make them up. Here’s an internal view of the short. There are two suboptimal things here, but I decided to ignore them.

1) One should use metal boxes That would short the braids with a lower inductance, but I had the plastic boxes and believe that the tags on the BNC connectors which are about 3 mm wide, are not going to present much inductance.

2) I shorted the inner conductors with a scrap of FR4 PCB. A bit of wide copper would have been better, but again I don’t think it will matter. At the maximum frequency (30 MHz), the wavelength is 10 m.?

The only difference between the open and short is that the open joins the two pairs of outer BNCs, but doesn’t short all 4.?

Tomorrow I will make up some proper labels for these.?

I also a photograph that I made some time ago to use with a 1 MHz 4284A. It has red and black connectors for the DUT - there’s no provision for adding DC bias. That seems to work okay with the 30 MHz 4285A. I intend making another of these, with 100 mm spacing between the connectors, to handle larger inductors.?

The LCR meter in the photographs in a 4284A, but the 4285A looks identical.?

Note, that you don’t need the open and short for the 4284 - only the 4285A. I don’t know what other LCR meters these are used with. Keysight discontinued the 4285A, and do not have a replacement.?

Dave

--

Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...

Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales, company number 08914892.
Registered office:
Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom

On Mon, 13 Apr 2020 at 01:53, Tam Hanna <tamhan@...> wrote:

Hello David,

may I have these pictures for my Instagram?

Sure

I would give you full credit of course.

I was going to ask that anyway. But feel free to use?

Tam

With best regards
Tam HANNA 

Dave

--

Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...

Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales, company number 08914892.
Registered office:
Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom

On Mon, 13 Apr 2020 at 02:01, Tam Hanna <tamhan@...> wrote:

Hello Dave,

giving credit is life blood. I treat my Instagram as a public rolodex, and hope that someone who needs sh*t you sell slinks over to your firm.

If he just does it, and does not even email me, I am even happier. I am not in it for ego...

Tam

I will create some better pictures later with some printed labels, rather then ones I scribbled with a pen.?

I have been thinking about how best to make a fixture able to handle a wide range of lengths of coils ?I was thinking of use earth blocks like these

?

Preferably not at Farnell prices!

Dave

--

Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...

Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales, company number 08914892.
Registered office:
Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom

On Mon, 13 Apr 2020 at 04:57, Jared Cabot via <jaredcabot=[email protected]> wrote:

Hi David.

?

Where did you get the BNC connectors for your open and short?
Were they taken from test fixtures or can they be purchased separately?

Thanks!

?

You can get them on eBay. Search for BNC levers or BNC handles. One does need to cut some BNC plugs up to make these, as you only want the inner part of the plug. I use a grinder and hacksaw.?

?

HP do make some fixtures with 4 levers, and some with none. Two is a compromise.

?

I want to make a fixture that allows one to apply a DC offset of up to 30 kV. That will be a challenge. I will probably restrict its use to a lower specification LCR meter I have, as I wrote not want to risk damaging these. At 30 kV, some precautions will be necessary.?

--

Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...

Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales, company number 08914892.
Registered office:
Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom

If you own a 30 MHz 4285A LCR meter, you may have discovered that you should perform a cable compensation if using 1 m or 2 m cables. You need

* Supplied 100 ohm resistor?

* 42090A open

* 42091A short?

The latter are over $1200 each. The 4285A LCR manual tells you how cobble together the open and short using BNC adapters if you don’t have the 42090A and 42091A, but I decided to make them up. Here’s an internal view of the short. There are two suboptimal things here, but I decided to ignore them.

1) One should use metal boxes That would short the braids with a lower inductance, but I had the plastic boxes and believe that the tags on the BNC connectors which are about 3 mm wide, are not going to present much inductance.

2) I shorted the inner conductors with a scrap of FR4 PCB. A bit of wide copper would have been better, but again I don’t think it will matter. At the maximum frequency (30 MHz), the wavelength is 10 m.?

The only difference between the open and short is that the open joins the two pairs of outer BNCs, but doesn’t short all 4.?

Tomorrow I will make up some proper labels for these.?

I also a photograph that I made some time ago to use with a 1 MHz 4284A. It has red and black connectors for the DUT - there’s no provision for adding DC bias. That seems to work okay with the 30 MHz 4285A. I intend making another of these, with 100 mm spacing between the connectors, to handle larger inductors.?

The LCR meter in the photographs in a 4284A, but the 4285A looks identical.?

Note, that you don’t need the open and short for the 4284 - only the 4285A. I don’t know what other LCR meters these are used with. Keysight discontinued the 4285A, and do not have a replacement.?

Dave

--

Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...

Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales, company number 08914892.
Registered office:
Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom

On Mon, 13 Apr 2020 at 20:20, Tam Hanna <tamhan@...> wrote:

Hello,

and it's off:

With best regards
Tam HANNA 

When I get some labels on them, I will send some photographs. I will also send a photograph of the 4285A, as the photo of the 4284A could confuse someone into thinking you need the opens and shorts for cable compensation of the 4284A, which you do not.? The two instruments look identical though.

The 4284A, all the lower frequency models and the higher frequency 4295A need opens and shorts for fixture compensation. But they are quite simple. Only the 4285A needs the additional ones I made, which is for cable compensation. On of the lower frequency models, you just set the cable length. I expect that's good enough for use to 1 MHz, but on the 30 MHz 4285A, which two stages of compensation are needed.

* Cables

* Fixtures