Swain Meter

QUESTION 1:
What is the minimum diameter of a conductor you can use a 14 inch inductive shunt and still be able to resolve 1mA?

ANSWER:
At our facility, we have accurately measured 1.002 ampere on a 28 gauge conductor inside of a clamp with 82” inside diameter. Please note that our test was under very controlled conditions and we were able to interrupt the current source to negate the earth field effect on the sensor. If your conditions are similar, you should not have a problem with measuring any size conductor in the 14” sensor. For measurements of small amounts of current, it is extremely important to negate the earth field effect. The earth field changes with time and position and must always be considered if current is not interrupted. If you have the ability to interrupt the current, earth field is not much of a problem, but an effort must be made to keep the sensor in exactly the same position with the current on and off. For small measurements you must also collect the baseline (with current off) once the meter reading is very stable and leave the current on long enough to get a very stable reading as well. The difference between the two readings will be the current in the conductor. Also, try to keep the conductor centered in the sensor. If the conductor is close to the openings, there will be error in the reading.