Multimeter  (220-0179)    Resistance Measurements     Faxback Doc. # 6268

The resistance measuring circuit compares the voltage gained through a
known internal resistance with the voltage developed across the unknown
measured resistance.

Before making resistance checks, be sure you remove power from and
discharge all capacitors connected in the circuit to be measure, then
follow these steps to make resistance measurements.

1.  Set the function switch to Kohms

Caution: Do not connect the test leads to a source of voltage when
         you set the function switch to Kohms.  Doing so might damage
         the multimeter.

Note:  During resistance checks, when there is not a specific
       resistance connected across the test leads, it is normal for
       the display to show OL (over-load indication) because the
       multimeter detects it as an infinite resistance.

2.  Connect the probes across the circuit to be measured.  The range
    automatically shifts to the one that gives the best reading.

Notes:

  During resistance measurements, an over-voltage circuit
  protects the multimeter (240V AC, 1 minute).

  When you short the test leads in the 400ohm range, the
  multimeter displays a small value (no more than 0.3ohms).
  This is due to internal circuit and test lead resistance.
  You might need to take note of this value and subtract it
  from the measured value when you measure a very small
  resistance.

  The current applied to a circuit during resistance measurements
  could damage some devices.  The applied voltage and current
  for each range is shown below.

Range            A*                B**              C***
400 ohms         2.99V             315mV            760 microA
4 K ohms         0.86V             183mV            335 microA
40 K ohms        0.58V             164mV            50  microA
400 K ohms       0.57V             165mV            5.7 microA
4 M ohms         0.53V             165mV            0.5 microA

*    A is the open circuit voltage at the jacks.
**   B is the voltage across a resistance equal to full scale value.
***  C is the current through a short circuit at the input jacks.

(RLR/smc-05/16/94)