Down / Smooth Button; Primary Function - Down; Secondary Function - Smooth - AEMC 5070 User Manual

Megohmmeter

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The calculation is performed as follows:

The insulation resistance varies with the measurement temperature. This depen-

dence can be approximated by the expression:

where:

Rc: Corrected Insulation Resistance to the reference temperature Rc

Reference Temperature

RT: Measured Insulation Resistance at Probe Temperature

KT: Coefficient T defined as follows:

KT = (1/2)

T: Probe Temperature

ΔT: T emperature change for which the Insulation Resistance is

divided by 2

Rc Temperature Reference: Temperature to which the Insulation

Example: A motor winding is tested at 1000V in a 68°F environment. At the

end of the timed test, the Insulation Resistance Value is 991 megohms. All the

historical data is at 104°F. The corrected Insulation Resistance value corrected

to 104°F for this motor is calculated by the Model 5070 to be 284.4 megohms

using the formula above when temperature correction is activated.

4.5 ▼ / SMOOTH Button

4.5.1

Primary Function - ▼

Decreases the value of the flashing parameter displayed or selects the next para-

meter down.

4.5.2

The SMOOTH function (activated by pressing the 2nd + SMOOTH buttons) acti-

vates/deactivates an insulation measurement digital filter.

Only the display is affected (which is smoothed), not the measurements. This

function is useful if the insulation values displayed are very unstable.

The filter is calculated as follows:

RSMOOTH = RSMOOTH + (R – RSMOOTH) / N

Since N is set to 20, the time constant of this filter is approximately 20 seconds.

Therefore, displayed results are presented more smoothly.

Rc = KT * RT

((Rc Temperature Reference-T) / ΔT)

Resistance measurement is adjusted

Megohmmeter Model 5070

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