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Measuring Stray Voltage


Stray voltage can be measured by a Digital Multi Meter (DMM) that has the capability to store events. I personally use a Fluke 189 DMM, which allows me to set the meter up at the test site and record over an extended time period all the electrical activity, without having to watch the meter or write down the readings. The 189 DMM will capture events as short one-quarter of a cycle (2 ms) duration set on Peak, Min, Max, and Average and retain that in internal memory. When set up to log True RMS data (an extremely easy feature to use) it will log all electrical events looking at three cycles and retain those events in the internal memory. The readings memory can be saved and viewed, at the test site, on the DMM display or downloaded to a computer where you can view the data or print it out both graphically and numerically.

Fluke has an application note titled "Is that a tingle she feels" [ PDF 180KB ]. The application note details how my wife and I used the Fluke DMM's to record the electrical activity, at the test site, over a 3-day period. We were able to actually see electrical events that happen so fast a human would not see it and the bar graph or the digital display may not show the events. However, the meter logging feature does capture and retain that activity in the internal memory.

Without the Fluke meters we would not have "tracked down" the stray voltage on our dairy farm, identified the source and most importantly, documented all the electrical events.

The Fluke Meters and software are extremely easy to use and allow you to use the factory preset settings or you can easily "customize" the meter settings on the meter or with the computer, to your specific needs.

The most important feature, to my wife and I, is the Fluke Technical Support. Fluke Tech Support will help you for FREE and answer all your questions and help you understand "ALL" the features and capabilities of the Fluke Meters and the phone call is free also (800 #). AND do not worry if your question is extremely simple or highly complex, they will help you to use the Fluke Meters and Fluke Software accurately and safely.

Fluke has training videos and CD's to teach you how to use the meters properly as well and I highly recommend them.

I am copying this email to Fluke. I am certain they will contact you directly.

I am willing to answer dairy stray voltage questions. I can certainly "talk cows" with any dairy person. They can call me at 507-839-3739 or email me at

Chuck Untiedt

Comment from Fluke Corporation


First, Chuck Untiedt has done a pretty good summary of how Fluke's 189 works - with one minor exception - while it is possible to view normal timed interval data stored in the meter on the front panel display, the shorter (50ms) event data may only be viewed after downloading to a computer - in the tables and graphs of the optional companion software, FlukeView Forms.

One alternative for viewing shorter events on the meter display is to use the meters MIN MAX recording function, however that will show only the single highest and lowest event that occurred over the recording period. The event-logging feature, on the other hand, will record hundreds of time-stamped events for later review after data is downloaded to a PC or laptop.

I know that Chuck, and wife Wanda, have both successfully setup these meters, recorded data, downloaded it to their computers, and then printed reports and analyzed the results. In one interesting case, I've seen logged meter data that tracked impulses in their ground measurements that resulted from passing thunderstorms - all time-stamped to correlate with the time of the passing storm.

In general, as I understand it, the test setup has consisted of selecting the AC volts measurement function, connecting the common test lead to an isolated ground rod away from farm buildings, and then connecting the Volts measurement lead to a point of interest (Cow contact, in the case of the dairy farm). In one case, I know they measured the voltage in the water flowing through plastic pipe into a plastic watering bowl during the time that the pump was running some distance away. Obviously, depending on the
application, one could make these connections between any two points of interest.

Fluke publishes several application notes and articles (available on our website) that describe the characteristics of the meter logging process and how that data is presented in a FlukeView Forms document on a PC.

An application note titled "Event logging with a Fluke 189" [ PDF 128KB ] which may be of some interest to you and your readers.

Finally Mike, I'd like to also take this opportunity to thank you for the forum you provide regarding such issues, and the valuable service you provide to electrical professionals in the pursuit of electrical safety.

Chuck Newcombe

Fluke Corporation

Mike Holt's Comment: The above was in response to my question on how to measure and record stray voltage.

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