Measuring the current in an electrosurgical unit

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Discussion Overview

The discussion revolves around the challenge of measuring current in an electrosurgical unit (ESU), specifically focusing on finding a suitable ammeter or current probe that can operate effectively at RF frequencies (350kHz-4MHz) and provide real-time measurements. The context includes the technical requirements for the device, including non-invasive methods and compatibility with computer systems.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant seeks a non-invasive ammeter for measuring current in an ESU, noting the difficulty in finding a commercially available device that meets the RF frequency requirements.
  • Another participant suggests using a current probe that can handle several MHz and high current levels.
  • A further response mentions the availability of clamp-on probes for oscilloscopes, but raises concerns about the complexity of using them with software like LabVIEW.
  • One participant points out that RF meters are available but typically operate at lower frequency ranges (10-50 MHz), which may not meet the needs of the original poster.
  • A suggestion is made to contact a specific company for potential solutions, indicating that they may have relevant products.
  • A later reply mentions Tektronix as a company that has provided a suitable current probe, although the participant does not endorse them or confirm receipt of products yet.

Areas of Agreement / Disagreement

Participants generally agree on the need for a specialized current measuring device for RF applications, but there is no consensus on a specific solution or product that meets all the requirements outlined by the original poster.

Contextual Notes

There are limitations regarding the availability of devices that can operate effectively at the specified RF frequencies and current levels. The discussion reflects uncertainty about the best approach to take and the potential need for custom solutions.

Who May Find This Useful

This discussion may be useful for individuals involved in medical device engineering, electrical engineering, or those seeking to measure RF currents in medical applications.

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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.
 
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You need a current probe. You can find plenty of them on market going up to few Mhz and several dozens of amps.
 
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.
 
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
 
thanks for your help. i am calling these companies. I will let you guys know when i find a solution.
 
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.
 

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