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Characteristic Impedance of BNC cable for BNC blocks

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Which impedance should the BNC cables have when they are connected to a BNC-2090A Connector Block?

 

Thank you.

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Accepted by topic author mmihovil@syr.edu

Typically BNC cables at 50 ohm characteristic but this matter only if the signal goes above several MHz.

Santhosh
Soliton Technologies

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Thank you for the answer. Our signal does go over MHz (80MHz for pulsed laser control), so this does matter to us. 

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Just make sure you get a good quality BNC coax cable, the cheap ones may not be 50 ohm.

 

Are you trying to capture 80MHz signal on a DAQ or count the pulses?

Santhosh
Soliton Technologies

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Sorry guys, simply using 50 Ohm cable to the BNC-2090A doesn't solve the impedance problem!

The 2090 is simply a mechanical adapter to the connected DAQ which mainly defines the input impedance. (with some 100 Ohm impedance for the twisted cable pair between the 2090 and the DAQ?)

The BNCs used seems to be 50 Ohm impedance ones.. BUT what the signal in the 50 ohm cable see as an impedance when 'hitting' the 2090 is not specified and I question that will be near 50 Ohm. That connector block is more for low frequency ...

 

If you want to do meaning full measurements in the  tenth of MHz region use hardware build for matched (50 Ohm) impedance. Add a powersplitter (resistive one DC to 2 GHz) and 50 Ohm terminations / feedthrougth to your shopping list.

 

Get a 10 (or higher)  MHz square wave source (with  50 ohm output impedance) hook it to a (100 MHz bandwidth) scope with and without 50Ohm termination , place some T connectors in between, add different cables ... see what that do to your signal.

 

 

   

 

 

Greetings from Germany
Henrik

LV since v3.1

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