Measuring the current in an electrosurgical unit

[nateg]

I have been trying to find an ammeter that can perform a specific task and failing miserably. I would appreciate any help I can get. and as you may soon notice, I have no engineering background.
I am trying to find a non-invasive method for measuring the current generated in an electrosurgical unit (ESU) - the device that powers a bovie electrocautery device. The device changes voltage to keep power constant, depending on the amount of current passing through the a patient (resistance is constantly changing). The current that is used is in RF frequencies (350kHz-4MHz), to limit the effects on heart electrophysiology, and runs between 200-1000mA.
I need a clamp on device that can be connected to a computer to give me real time measurements of the current while the bovie is in use.
I cannot find an ammeter that will operate in RF frequencies and within those parameters.
Does anyone know of a device commercially available that can do this? Does this type of device have to be custom built?
I would appreciate any help I can get... thanks.

 

[zoki85]

You need a current probe. You can find plenty of them on market going up to few Mhz and several dozens of amps.

 

[nateg]

If you know of one that you think could work, I would really appreciate it. I have been trying to find one for some time and I cannot. Please let me know.

 

[Mike_In_Plano]

There are a variety of clamp-on probes intended for use with oscilloscopes. Of course, oscilloscopes are a natural instrument to visualize and measure in this range, but setting the ranges, zeroing, and capturing the information via labview might be a mess.

RF meters are readily available that will plug into the 50 ohm outlet of the probe. Unfortunately, these tend to have a lower range between 10 and 50 MHz.

So, as far as I've found you're either stuck with a PC controlled scope and probe or a probe with a custom RMS converter.

Sorry I couldn't cook up something easier.

- Mike

 

[meBigGuy]

I'd talk to these guys to start with:
http://www.powertekuk.com/cwt.htm

 

[nateg]

thanks for your help. i am calling these companies. I will let you guys know when i find a solution.

 

[nateg]

I am not endorsing any company. And I have not received any products yet. But, Tektronix was the only company that was able provide/sell an appropriate current probe. They were also very helpful. FYI, if anyone needs something similar.