How to make more accurate high resistance measurements
QWhat should I be aware of when measuring high resistances more accurately with the Super Megohm Meter SM7110?
For stable measurement of high resistance, it is necessary to take measures against error factors such as noise and leakage current.
Please refer to the following notes for measurement:
- Leakage current
When measuring high resistance, guard it with a dedicated shielded measuring cable.
In this way, leakage current flows through the shield. Therefore, the leakage current does not pass through the current detection circuit in the instrument and does not affect the measured value.
- Friction noise
When measuring high resistances with a Super Megohm Meter, friction noise in the measuring cable can lead to errors. Since moving the measuring cable can cause loud noise, use low-noise cables that do not generate much noise.
- External noise
Electromagnetic external noise emitted from fluorescent lights, motors, and other sources can make measurements unstable.
Fluorescent lamps and commercial power lines are electrostatically coupled to the measurement leads and affect the measurement results, especially in high-resistance measurements where the detection current is small. External noise due to electrostatic coupling can be reduced by shielding the measurement leads. Magnetic fields radiated from transformers, etc., are magnetically coupled to the measurement leads and become external noise. External noise due to magnetic coupling can be reduced by making the loop of the measurement lead as small as possible or by moving the measurement lead away from the source of the magnetic field.
- Temperature change
Relatively large changes in ambient temperature will cause the displayed value of the instrument to fluctuate, resulting in a measurement error. Use within the guaranteed temperature range. When used in an environment outside of that range, multiply the accuracy range by the specified temperature coefficient. (Temperature coefficients are listed in the instruction manual that comes with the product.)
Also refer to the User's Guide.
Insulation Resistance Measurement Handbook
Hioki Super Megohm Meter SM7110, SM7120, SM7420, SM7810