Clamp-on ammeter

[Sibi]

Hello all,

I have an NI USB 6009 product with me. I'm planning to use it for measuring the current on a prototype motherboard.
I have a few questions. I'd be thankful if you can answer these:

1) Has anyone used a clamp-on ammeter with USB 6009 before? If yes, which product?

2) The USB 6009 spec says that it's input impedance is 144KOhms. Typical clamp-on ammeters say that they are compatible
with Digital Multimeters with input impedance of several Mohms. Would such a clamp-on ammeter be compatible with the USB 6009? Do I have to perform impedance matching?

3) Also, typically, the ammeters have test leads that fit into a DMM. How do we connect the ammeter to the USB 6009? Is there an adaptor available or can I just snip off the ends of the test leads and connect it to the USB 6009?

Thanks in advance,
G.Sibi

[Erik_J]

Hi G.Sibi,

1) I have not used a clamp-on ammeter with the NI USB-6009 before, but it should work.

2) You should not have to perform impedence matching.

3) I don't know of any specific adaptor, but I would suggest to use alligator probes to clamp onto the wires in the NI USB-6009.  An ammeter usually takes a measurement by being in series with the circuit.  Meaning you would be required to break the circuit somewhere and insert the ammeter.

Regards,
Erik J.

[gwd]

The whole idea of a clamp-on ammeter is that you DON'T have to break the circuit.

Probably it will work fine. They are telling you the output resistance is low enough that megohm loads do not cause significant error. It MAY be low enough to work OK with 100 k loads.

You can

- look in the specifications (they may specify output resistance)
- try it by measuring the same current using a DMM and the USB to read the current.

[psgeorge]

I am currently using a clamp-on ammeter with the USB 6009.  I am using the model M1V-20-1 microclamp from Flex-Core (www.flex-core.com) along with their model RMS-01 true RMS converter to measure high currents.  They have models which will measure up to 300 amps.  I've had no problem with it.  Check out their website.

[Sibi]

Hi,

Thanks for the flex-core URL. I'll check it out. I see that these flex-core clamps have BNC leads. How did you adapt them for USB 6009? I know that there are BNC-to-banana plug converters, but I couldn't find any banana-to-normal wire adapter to connect with the USB 6009. What solution did you use?

Thanks,
G.Sibi

[psgeorge]

The microclamp has banan-clip female connectors which mate with the male banana-clip plugs on the RMS-to-DC-converter which has a BNC female output connector.  You can rig a cable with a bnc male connector to connect to the USB 6009.  My application is a QC test program to measure the amps of various components (motors, heaters, compressors, etc.) of a large cooling unit under controlled conditions on the factory test floor.  A .net windows application developed using NI's Measurement Studio prompts the user to place the probe and then take a measurement.