Revised August, 2004
10 TEGAM WAY • GENEVA, OHIO 44041 • 440-466-6100 • FAX 440-466-6110
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3-2
OPERATING INSTRUCTIONS
3.2
General Theory Of Operation
A 2-terminal measurement method is used to determine the
resistance of the item under test. The R1M-A calculates the
resistance of the item under test utilizing Ohm's law and
displays it on a 3 ½ digit display.
To obtain the best accuracy, allow the R1M-A to warm up for
15 to 30 minutes before making measurements. In any case,
a minimum warm-up of 30 seconds is advised.
Depress the TEST pushbutton, which switches on the high
voltage. Note that the red LED will light, indicating that high
voltage is present on the terminal. Allow for a brief settling
time and read the resistance on the digital display. Note that
the operating range of resistance values which may be read
on any given range extends from 5% to 199.9% of the
nominal value of the selected range. Note that readings
greater than 100% will take more time. Thus, the 1 MΩ
range may be used to measure resistors from 50 kΩ to
1.999 MΩ. Note that the test voltage must be 50 V for
resistances less than 1 MΩ. If the resistance measured
exceeds the maximum value for the selected range, the
display will show blanks; in that case, set the range switch to
a higher range. If the resistance measured is less than 5% of
the nominal value of the selected range, the display will
show a minus sign; if so, switch to a lower range, since the
readings may be inaccurate.
If readings are noisy, especially at very high values of
resistance, it may be caused by 60 Hz coupled to the test
resistance from the power line. Note that at 100 GΩ, an
extremely small capacitance will couple many volts into the
test resistance from a power line. If so, it may be necessary
to interpose a grounded shield plate or to put the unknown
resistor into a metal box, connected to the GUARD alligator
clip.
To close up the R1M-A, first reattach the lid to the main
case, if it has been removed. Then store the power cord and
test cables in the side compartment.
