Test leads and dual banana female jack to male BNC adapter

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KimAndersen
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Test leads and dual banana female jack to male BNC adapter

Post by KimAndersen »

I would like to share some hard earned experience with you picoscope users.

As this topic title shows has it somethings to do with the combination of a picoscope test leads and a dual banana female jack to male bnc adapter manufactured bye Fluke (PM9082) and a milliamp current clamp (K2) which I used to measure a wideband oxygen sensor.
FLUKE PM9082 BNC TO FEMALE BANANA (PLASTIC)
FLUKE PM9082 BNC TO FEMALE BANANA (PLASTIC)
It´s nearly two years ago since I buyed a current clamp (500 mA) and a very expensive dual banana female jack to male bnc adapter (PM9082) - this banana plug cost the double of a ordinary banana female jack - my thoughts about this Fluke banana plug were very high as Fluke are a good brand.

When you are measuring a wideband oxygen sensor in the range of +- / 2mA and are using a current clamp with a of conversion factor of 10mV/1 mA - you must be absolut sure that your test leads and current clamp are fully connected to your picoscope without any loose connections.

This current clamp are connected directly to the picoscope with this dual female jack in between those two units. When the current clamp are connected - must you reset this by turning the knob in the bottom of the current clamp.

Now the milli amps readings suddenly drift or sometimes the they are higher or lower - I try to reset the clamp again and reposition it, but with the same result. What else could make this happen - off course if the the test leads from picoscope are loose in the BNC connector or the leads are damage in any way, but they are in fine condition and fits the BNC connector very well.

I was sure that this millimap reading from the picoscope was wrong, but I couldnt find any solution to this problem and there is nothing as mistrust to your equipment and how it operates. The pattern was diffrent every time you connected the current clamp - very frustrating. As the milliamp current clamp and dual banana female was new, I was sure that those units were just fine.

Then by accident or not did I look at the picoscope and at the same time did I observe the dual banana female bnc jack when I pushed this a bit and to my big surprise could see some big changes in th signal at the picoscope.

My first thought was a loose BNC connector, but that was checked earlier and this was very tight, so it couldn't be that !!!.

Next thing I did was to take a closer look at dual banana female BNC jack and to be more specific at the BNC adapter and how it connects to the picoscope BNC adapter.

We all know at the BNC adapter on the picoscope is made by a metal at the outerside of the BNC and which are connected to the black test leads of the picoscope and finally connected to ground of the picoscope.

Then I got suspecius to the black colour of this Fluke PM9082 dual banana female jack to male BNC adapter and the matriale it´s made of and to my big suprise - was it made of plastic !!!!!!!.

Just to sum this up.I now know why the signal changes so much and it's because it loses the metal to plastic connection on the BNC adapter - that's why !!!.

If I may give a advice regarding the use of dual banana female BNC to male adapter - use this adapter instead which also is from Fluke (BP880_BNC_TO_FEMALE_BANANA). This bnc adapter is made of metal on the outside which give electrical connection all the time.
FLUKE BP 880 BNC TO FEMALE BANANA (METAL)
FLUKE BP 880 BNC TO FEMALE BANANA (METAL)
Here at the end I will just say - always check your test leads and other equipment you are using for any damages. Also doubt the signal you are getting on the picoscope as in my case - I was so close to replace that oxygen wideband sensor with a new one on the basis of this weird looking sensor signal.

Regards
Kim

Steve Smith
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Re: Test leads and dual banana female jack to male BNC adapt

Post by Steve Smith »

Hello Kim and thank you for taking the time out to share this glitch.

Such events can turn what should be a rapid measurement into hours of confusion with no outcome.

Something you mentioned also rang true and I often quote when we believe we have found a fault or an anomaly.

"Always check your test leads and other equipment you are using for any damages. Also doubt the signal you are getting on the Picoscope as in my case"

To follow up on the above, always blame your measurement technique, equipment, connection or test condition when you find something wrong. Once you have proven all the above are OK, what you have found is a true and relevant fault.

Thank you again Kim

Take care.......Steve

martinr
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Joined: Tue Mar 06, 2018 4:06 pm

Re: Test leads and dual banana female jack to male BNC adapter

Post by martinr »

Thank you very much, Kim. What an excellent, helpful post. That is certainly something I’m going to look at, although my current clamp has a BNC connector. I deliberately did not buy any clamps with banana connectors because of the possibility of problems with any interface. But I do need to look at the possibility of a bad BNC connector. And I also have one of those Fluke banana-to-BNC connectors. I need it for my Fluke pressure transducer to connect, so your post was valuable even if the BNC connection is not the cause of my problem.

Thanks again, very valuable information.

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