Impedance measurement clamp - URGENT - diyAudio
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Old 20th August 2003, 09:22 AM   #1
Vikash is offline Vikash  United Kingdom
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Default Impedance measurement clamp - URGENT

I'm building a clamp to hold drive units for impedance measurements today. The material at hand is mild-steel rectangular tubing.

I'm worried about the magnetic flux in the air gap being affected when the metal tube is in direct contact with the driver magnet assembley. Will this affect impedance measurements of the driver? i.e. do I need to use a non magnetic material to actually clamp the driver?
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Old 20th August 2003, 10:15 AM   #2
Doug is offline Doug  Canada
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I use a Workmate opened up enough to mount the driver on its back firing upwards. I put a couple of rubber pads between the Workmate and the driver with just 2 small clamps ( one on each side of driver ) to keep it from vibrating, especially during resonance. I always get a nice clean impedance curve using the LMS system.

Works for me
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Old 20th August 2003, 10:38 AM   #3
Doug is offline Doug  Canada
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PS:

The clamps I use are the plastic squeeze on types found at any build it center eg. Home Depot. I use various sizes depending on the size of the driver being tested.

In case you don't know what I mean by a Workmate in the UK I've attached a photo.
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Old 20th August 2003, 10:47 AM   #4
Doug is offline Doug  Canada
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Here is a photo of the clamps I use.
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Old 20th August 2003, 11:03 AM   #5
Vikash is offline Vikash  United Kingdom
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Hi Doug,

Quote:
mount the driver on its back firing upwards
I've read several references that recommend measuring the driver in its natural position i.e. firing forwards.

Since I've got the materials and will probably be doing this a lot, I want to build a dedicated jig for driver measurement. It should have the ability to hold a driver 3' in the air, firing forward , and handle magnet assemblies up to 25cm diameter (my sub magnet is 20cm).

This is my idea:
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Old 20th August 2003, 11:04 AM   #6
Vikash is offline Vikash  United Kingdom
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pic
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Old 20th August 2003, 11:40 AM   #7
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That looks very posh!

I use this...
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Old 20th August 2003, 12:09 PM   #8
Vikash is offline Vikash  United Kingdom
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Oh that's just me getting carried away as usual. My approach is to just go OTT and never have to worry about it again.

I think I'll settle for this inherently more sturdy design, and i won't have to worry about anything touching the magnet assembly either.
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Old 20th August 2003, 12:21 PM   #9
-CGL- is offline -CGL-  Finland
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Hi. Im using an engine vise and a large bench vise. Like the one in the link.

http://www.linearx.com/products/soft...p/EncShp05.htm

Mid page.


CL
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Old 21st August 2003, 10:29 AM   #10
Doug is offline Doug  Canada
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I've read several references that recommend measuring the driver in its natural position i.e. firing forwards.

Vikash;

I've made the impedance measurements with driver facing upwards and foreward but have not noticed any difference in the impedance plot.

Awesome looking designs you came up with though

Doug
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