Working principle and operation steps of portable anti-corrosion layer insulation resistance measuring instrument

Used to evaluate the insulation performance of anti-corrosion coatings on buried metal pipelines, cables, etc., its operating principle is based on insulation resistance testing technology. The core method is to apply a high DC voltage and measure the leakage current, and calculate the insulation resistance value according to Ohm's law.‌

working principle

The internal DC high-voltage generator of the instrument generates a stable DC voltage (such as500VThe1000Vor2500V）Applied between the surface of the anti-corrosion layer and the metal conductor. At this point, the anti-corrosion layer, as an insulating medium, will generate a small leakage current. The instrument detects this current through a measurement circuit and uses the formula to( R = U/I )(Resistance)=voltage/Calculate the insulation resistance value (usually in megaohms) based on the current.‌

2 For example, applying1000VIf the leakage current measured during voltage is1μAThe insulation resistance is1000MΩ.‌

1 For buried pipelines, this principle combined with electromagnetic induction technology can non destructively locate the damaged points of the anti-corrosion layer.‌

operating steps

‌Preparation before measurement‌Ensure that the power supply of the tested equipment (such as pipelines) has been cut off and short circuited to ground for discharge. Clean the tested surface to reduce contact resistance.‌‌Instrument inspection‌Conduct open circuit and short circuit tests on the megohmmeter - the pointer should point to "∞" during an open circuit and to "∞" during a short circuit“0To confirm that the instrument is functioning properly.‌

‌Wiring method‌：

‌Lterminal‌(Line end): Connect the tested conductor (such as pipeline core).

‌Eterminal‌(Grounding terminal): Connect the pipe casing or grounding body.

‌Gterminal‌(Shield end): Connected to a shielding layer or protective ring, used to eliminate surface leakage interference (used when measuring cables or precision equipment).‌

‌measurement process‌：

Keep the instrument level and shake the handle (or power on) clockwise, gradually increasing the speed from slow to fast120turn/minute.

Continuous shaking15-60Wait for the reading to stabilize and record the insulation resistance value. If the pointer points to zero, it indicates that there may be a short circuit and the shaking should be stopped immediately.‌‌Measurement post-processing‌After the reading is completed, discharge the tested equipment (such as short circuiting with a ground wire) to ensure safetycomplete